Recommended Machining Parameters for Copper and Copper Alloys

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Recommended machining parameters for copper and copper alloys

DKI Monograph i.18 Issued by: German Copper Institute / Deutsches Kupferinstitut Information and Advisory Centre for the Use of Copper and Copper Alloys Am Bonneshof 5 40474 Düsseldorf Germany Tel.: +49 (0)211 47963-00 Fax: +49 (0)211 47963-10 [email protected] www.kupferinstitut.de

Print run 2010

Revised and expanded by: Laboratory for Machine Tools and Production Engineering WZL at RWTH Aachen University Prof. Dr.-Ing. Dr.-Ing E.h. Dr. h.c. Fritz Klocke Dipl.-Ing. Dieter Lung Dr.-Ing. Klaus Gerschwiler Dipl.-Ing. Patrik Vogtel Dipl.-Ing. Susanne Cordes Fraunhofer Institute for Production Technology IPT in Aachen Dipl.-Ing. Frank Niehaus

Translation: Dr. Andrew Symonds BDÜ

Picture credits: TORNOS, Pforzheim; Wieland-Werke, Ulm

Kindly supported by International Copper Association, New York Contents

Contents...... 1 6 Cutting-tool geometry...... 35 Foreword...... 2 6.1 Rake and clearance angles...... 35 1 The situation today...... 3 7 Cutting fluids...... 37 2 Fundamental principles...... 5 8 Calculating machining costs...... 38 2.1 Tool geometry and how it influences 9 Ultra-precision machining of copper...... 40 the cutting process...... 5 9.1 Principles of ultra-precision machining...... 40 2.1.1 Tool geometry...... 5 9.2 Example applications involving copper alloys.40 2.1.2 Effect of tool geometry on the 9.3 Work material properties and their cutting process...... 6 influence on ultra-precision machining...... 41 2.2 Tool wear...... 10 10 Recommended machining parameters 2.3 Chip formation...... 11 for copper and copper alloys...... 43 3 Machinability...... 13 10.1 Turning of copper and copper alloys...... 43 3.1 Tool life...... 13 10.2 Dr illing and counterboring of copper and copper alloys...... 44 3.2 Cutting force...... 15 10.3 Reaming copper and copper alloys...... 46 3.3 Surface quality...... 18 10.4 T apping and thread milling copper 3.4 Chip shape...... 21 and copper alloys...... 46 4 Classification of copper-based 10.5 Milling copper and copper alloys...... 47 materials into machinability groups...... 23 11 Appendix...... 49 4.1 Standardization of copper materials...... 23 11.1 Sample machining applications...... 49 4.2 Machinability assessment criteria...... 23 12 Mathematical formulae...... 56 4.3 The effect of casting, cold forming and age hardening on machinability...... 24 12.1 Equations...... 56 4.4 Alloying elements and their effect 12.2 symbols and abbreviations...... 58 on machinability...... 25 13 References ...... 61 4.5 Classification of copper and copper alloys 14 Standards, regulations and guidelines...... 63 into main machinability groups...... 28 5 Cutting-tool materials...... 32 5.1 High-speed steel...... 32 5.2 Carbides...... 32 5.3 Diamond as a cutting material...... 33 5.4 Selecting the cutting material...... 34

DKI Monograph i.18 | 1 Foreword

“Recommended machining parameters Like its predecessors, this edition of for copper and copper alloys” contin- the handbook has been designed to ues a long tradition established by address the concerns of practitioners, the German Copper Institute (DKI). The helping them to find the most effec- publication “Processing Copper and tive and economical solutions to their Copper Alloys” (“Das Bearbeiten von metal cutting problems. It also aims Kupfer und Kupferlegierungen”) first to assist designers and development appeared in 1938 and again in 1940. engineers when comparing the machin- The handbook “Metal cutting tech- ability of different materials, making niques for copper and copper alloys” it easier for them to estimate the fab- (“Die spanabhebende Bearbeitung rication costs of a particular part. Ma- von Kupfer und Kupferlegierungen”) chinability index ratings have therefore by J. Witthoff, which was published in been added to the tables included in 1956, represented a thorough revision the handbook. Machinability ratings and rewriting of the earlier work. The are commonplace in the specialist new handbook included for the first literature and not only help to make time a complete overview of all the comparisons between different copper standardized copper materials and materials but also comparisons with metal cutting data known at the time. other metallic materials such as steel In addition to the easily machinable or aluminium. free-cutting brass, the handbook also gave an account of copper alloys that The tables have also been brought had been developed for specific appli- up to date to reflect the most recent cations and that were often far harder materials standards, and the tables to machine. In 1987 large sections of reference values for the various of the handbook were reorganized, machining methods have been revised revised and updated by Hans-Jörn and expanded. As the machinability Burmester and Manfred Kleinau and of a material is highly complex and re-issued under the current title depends on a large number of fac- “Recommended machining parameters tors, the benchmark values provided for copper and copper alloys” (German here can only offer broad guidance. To original: “Richtwerte für die spanende establish the optimal machining pa- Bearbeitung von Kupfer und Kupferle- rameters for a specific production pro- gierungen”). The handbook included cess and thus optimize the productivity recommended machining parameters and cost-efficiency of that process, for all relevant machining techniques additional cutting and machining tests for a broad range of copper alloys. under the actual production conditions must be carried out. In order to take account of recent technical developments in the field, the handbook has once again been revised and updated while retaining the previous title.

2 | DKI Monograph i.18 1 State of the art

Compared to other metallic structural als. In order to meet a very wide range ters for the machining of copper and materials, most copper-based materials of technical and engineering require- copper alloys – particularly in view of are relatively easy to machine. The free- ments, a great number of copper-based the ongoing developments in the metal cutting brass with the designation materials have been developed over cutting sector. Furthermore, optimizing CuZn39Pb3 has established itself as the years. Examples of more recent machining operations by selecting and an excellent material for manufactur- developments include the low-alloyed adapting the relevant machining data ing all kinds of form turned parts. The copper alloys, copper-nickel alloys and is of huge commercial importance in excellent machining properties of these lead-free copper alloys. The spectrum high-volume serial production. copper-zinc alloys is so well-known of materials available ranges from the that they are often used as benchmarks high-strength copper-aluminium alloys Material development is focused on for describing the machining properties to the very soft pure coppers with their the continuous improvement of a of copper and copper alloys high elongation after fracture. material’s properties. In order to lower machining costs, fabricators frequent- Machining copper alloys is considerably The differences in the machinability ly demand materials with improved easier than machining steels or alumin- of one material compared to that of machinability properties but with ium alloys of the same strength (see another can be traced to the differences mechanical and physical properties that Figure 1). This is reflected in the signif- in their mechanical and physical prop- are essentially unchanged. Examples icantly lower cutting forces as shown erties. Many machine operators have of this trend are the CuTeP and CuSP in Figure 2. Unless specific technical only a limited knowledge of the ma- alloys. Although pure copper has very requirements dictate the use of another chinability of the less commonly used high conductivity values, the fact that it material, free-cutting brass CuZn39Pb3 copper materials. As a result, the ma- produces long tubular or tangled chips Abb. 1: Vergleichis the material der of Zerspanbarkeit choice in contract chining data von assumed Kupferwerklegierungen for one and the can make it difficult to machine. For mit einem turning and machining shops and CNC same material may differ considerably this reason alloys have been developed Automatenstahlturning und shops. einer Aluminiumlegierungfrom one machining shop to another. [THIE90 in which ,tellurium, DKI10 sulphur, or WIEL10] lead There is therefore a very definite need have been added to the pure copper Parts that are mass-manufactured are for up-to-date reference values and as chip-breaking alloying elements. typically machined from copper materi- recommended processing parame- The conductivity of these alloys is only

100 * 80 ex d *** tsin 60 rkei a * anb p 40 * * ers Machinability index Machinability Z

20 ** * AL Stahl 0 CuZn36Pb3 CuZn21Si3P CuZn35Pb1 CuZn39Sn1 CuZn36* AlCu6BiPb 11SMnPb3 (Cu Zn39Pb3) WerkstoffMaterial

** Zerspanbarkeitsindex CDA machinability ratings gemäß using CDAthe ASTM nach E618 Testmethode test method with ASTM CuZn36Pb3 E618 mit as CuZn36Pb3 the reference als material Referenzwerkstoff(in Europe the reference (in Europa material ist is der the Referenzwerkstoffcopper-zinc alloy CuZn39Pb3) die Kupfer-Zink-Legierung CuZn39Pb3) **** CCuZnuZn36: 36 :Machinability Zerspanbarkeitsi rating ndex based nach on the DKI DKI Werksto materialff ff datenblattdata sheet *** CuZn21Si3P: Machinability rating as specified by manufacturer *** CuZn21Si3P: Zersppganbarkeitsindex nach Herstellerangabe

Fig. 1: Comparison of the machinability of copper alloys with a free-cutting steel and an aluminium alloy [1, 2, 3] Quell e: * Compara tive Mac hina bility of fB Brasses, St eel s and dAl Alumi num All oys: CDA‘ CDA‘Uis Universal lM Machi nabilit bilitIdy Index, www.copper.org, DKI Monograph i.18 | 3 **CuZn36: Zerspanbakrisindex nach DKI Werkstoffdatenblatt ***CuZn21Si3P: Zerspanbarkeitsindex nach Herstellerangabe (Wieland)

v k 1-m MaterialWerkstoff c c1.1 c m/min N/mm² CuZn39Pb3 200 539 0,7886 2000 Free-cuttingAutomatenmessing brass 400 521 0,7458 ²)

m 200 1137 0,8211 mm m 1500 CuSn8P

N/ Kupfer-Zinn-Legggierung ( Copper-tin alloy 400 1020 0,8059 / /

c CuZn37MnAl2PbSi 200 845 0,7561 t k f SpecialSondermessing brass

ra 400 715 0,7036

k 1000 tt i 16MnCr5+N n 200 1302 0,7092 h Case-hardenedEinsatzstahl steel c S Specific cutting force Specific cutting z. CuZn 39P b3 N10 - N20 e

p CuSn8P α = 7°; γ = 0°; λ = 0° s ο ο σ vc = 200 m/min CuZn37MnAl2PbSi κr = 93°; εr = 55°; 500 vc = 400 m/min rε = 0,4 mm; ap = 1 mm 16MnCr5+N P10 010,1 020,2 040,4 060,6 101,0 202,0 αο =5= 5°; γο =6= 6 °; λs =0= 0 ° UndeformedSpanungsdicke chip thicknessh/mmh / mm κr = 70°; εr = 90°; rε = 0, 8 mm; ap = 3 mm

Fig. ©2: WZL/Fraunhofer Comparison of IPTthe specific cutting force of three copper alloys with a case-hardened steel based on data from DKI and from reference [4]Seite 3 slightly below that of pure copper, but ting tool materials makes it difficult and recommendations provided in this the presence of the alloying elements for today’s manufacturers to provide handbook can help machine operators means that they can be processed on recommended cutting parameters or to find the optimal machining parame- automatic screw machines or other benchmarks that remain valid for a ters for a specific machining task. If only high-speed machine tools. longer period of time. If supplement- low-volume production is required, ed and/or verified by cutting tests the reference values provided in the The continuous improvements being conducted under realistic machining handbook should be sufficient to yield made to both workpiece and cut- conditions, the guideline parameters a satisfactory machining result.

4 | DKI Monograph i.18 2 Fundamental principles

In this section explainations are given on the basic terminology of metal Direction of primary cutting relating to cutting tool geo- WerkzeughalterTool holder Schnittrichtungmotion metry, tool wear and chip formation, using a standard turning tool (single- point cutting tool) for illustrative purposes. The terminology applies equally to any other machining procedure that uses a tool with a defined cutting DirectionVorschubrichtung of feed motion edge. Being acquainted with the basic SSpanRake fläfaceche h Aγ Major cutting edge terminology is fundamental to under- Hauptschneide S S standing the machining properties of Minor cutting HauptfreiflächeMajorp flank face Aα Aα ‘copper and copper alloys. Nebenschneideedge S، S CornerSchneidenecke ، 2.1 Tool geometry and how it MinorNNebenf bflank fre ifläfaceche h A A‘αα influences the cutting process

Fig. 3: Face, flanks, cutting edges and corner of a turning tool (DIN 6581) The fundamental terminology of metal cutting technology has been standardized in DIN 6580, DIN 6581, DIN 6583 and lative orientation of these surfaces to one The tool-in-use system is defined in DIN 6584 standards. The surfaces and another determines the tool angles. relation to the relative speeds of the cutting edges of a single-point cutting cutting tool and the workpiece during tool are shown in Fig. 3. To explain the terms and angles used the machining operation. The working to describe a cutting tool, it is useful to reference plane Pre passes through a distinguish between the so-called ‘tool- selected point on the cutting edge and 2.1.1 Tool geometry in-hand’ system and the ‘tool-in-use’ is perpendicular to the resultant cutting As Fig. 3 shows, the cutting part of a system (see Fig. 4). The two systems are direction. The orientation of the resultant turning tool comprises the rake face and based on different sets of orthogonal cutting direction is given by the resultant Abb. 4 (()athe) Wirk-major and minor und flank (() faces.b) WerkzeuThe re- referenceg planes.-Bezuggysystem (nachof the cutting DIN and feed 6581 speed vectors.)

Resultant cutting Wirkrichtung direction Direction of primary Assumedangenommene direction of Schnittrichtung motion Schnittrichtungprimary motion v ve c Werkzeug- WorkingWirk- cutting WorkingWir k- Tool cutting edge Orthogonal- Schneidenebene edgeSchneidenebene plane Pse orthogonal plane Ps ebene Ps Pse plane Poe Poe Assumedangenommen directione DirectionVorschub- of feed ofVorschubrichtung feed motion WkWTooler korthogonalzeug- richtungmotion Orthogonalebeneplane Po Selectedbetrachteter point on P vf o cuttingSchneidenpunkt edge

AuflageebeneTool base AuTool flagee base bene WkWerkzeug-BbBezugsebene WorkingWirk-Bezugsebene reference Toolsenkrecht reference zur plane ang enommenenperpendicular planesenkrecht perpendicular zur toSchnittrichtung assumed direction und of parallel primary toWirkrichtung resultant cutting motionzur Au and flagee parallel bene to tool base Pr directionPre Pre a b Pr

Fig. 4: (a) Tool-in-use reference system (b) Tool-in-hand reference system (DIN 6581)

DKI Monograph i.18 | 5

© WZL/Fraunhofer IPT Seite 5 In the tool-in-hand system, the tool The sum of these three angles is cutting tools with a geometrically reference plane Pr is parallel to the tool always 90°: defined cutting edge. base. The tool cutting edge plane Ps is tangential to the cutting edge and αo + β o + γ o = 90° (1) perpendicular to the tool reference plane 2.1.2 Effect of tool geometry on the Pr. The geometry of the cutting tool is ● The tool cutting edge angle κr is the cutting process measured in the tool orthogonal plane angle between the assumed direction The choice of cutting angles has a Po. This plane passes through the select- of feed motion and the tool cutting major effect on the results of a ma- ed point on the cutting edge perpendic- edge plane Ps measured in the tool chining operation and on the tool life. ular to both the tool reference plane Pr reference plane Pr. The greater the emphasis on achieving and tool cutting edge plane Ps. cost-effective material processing, the ● The tool included angle εr is the greater the importance of determining In the tool-in-hand system, the angles angle between the tool cutting edge an optimal tool geometry. The stability of the wedge-shaped cutting tool are plane Ps and the tool minor cutting and therefore the life of the cutting defined as follows (see Fig. 5): edge plane Ps' measured in the tool tool can be raised by selecting ap- reference plane Pr. propriate cutting angles and by using ● The tool orthogonal clearance αo chamfered and rounded cutting edges. is the angle between the flank Aα and ● The tool cutting edge inclination λr Optimizing the geometry of a cutting the tool cutting edge plane Ps mea- is the angle between the major cutting tool always means taking into account sured in the tool orthogonal plane Po. edge S and the tool reference plane the specific requirements of the ma- Pr measured in the tool cutting edge chining operation to be performed and ● The tool orthogonal wedge angle plane Ps. the machining conditions to be used. βo is the angle between the flank Aα and the face Aγ measured in the tool We have chosen here to describe the It is also important to remember that orthogonal plane Po. terminology and tool angles using a the effect of modifying tool angles is single-point cutting tool, specifically a two-fold. Changing the tool angles ● The tool orthogonal rake γo is the turning tool, as it permits the clearest to strengthen the tool impairs chip angle between the face Aγ and the tool illustration of the different quantities. formation and increases the cutting reference plane Pr, measured in the In principle, however, the definitions forces and the extent of tool wear. Abb.5tool Wichtigste orthogonal plane Winkel Po. am Schneidteilprovided here can (nach be applied DIN to 6581)all Conversely, changing the tool angles to

SectionSchnitt A — AA –in A the A Aγ plane P Z in Po o Aγ

Aα A - κr

εr +

- +

Aα

View alongAnsicht Z in theZ αo = ToolOthOrth ogonaorthogonal lfilfreiw ikliclearancenkel planein P sPs γo = Tool Orthogonalspanwinkel orthogonal rake βo = ToolOrtho orthogonalgonalkeilwinkel wedge angle κr = ToolEinstellwinkel cutting edge angle εr = ToolEkEckenw included iklinkel angle λs = ToolNeigungswinkel cutting edge inclination Aα = FlankFreifläche Aγ = FaceSpanfläche P = Tool Werkzeug reference-Bezugsebene plane λs r - Po = ToolWerkzeug orthogonal-Orthogonalebene plane + Ps = ToolWerkzeug-Schneidenebene cutting edge plane

Fig. 5: The most important tool angles (DIN 6581) © WZL/Fraunhofer IPT Seite 6

6 | DKI Monograph i.18 improve chip formation results in a de- to improve chip formation and chip the clearance can be increased. As the crease in tool strength and hence tool removal. clearance angle increases, heat can life. Any choice of tool angles therefore build up in the tool tip thus increasing represents a compromise that can only When machining copper materials with the risk of material break-out at the partially meet the different machining a high-speed steel cutting tool, the tip. The bending moment resistance requirements. It is important that this clearance is typically between 6° and of the tip also decreases strongly with is understood when using the tables of 8°; if a cemented carbide cutting tool increasing clearance angle. recommended tool geometry parame- is used, the clearance lies in the range ters included in this handbook. The 8° to 10°. Large clearances tend to Of all the tool angles, the tool rake γ0 recommended tool geometry will also reduce flank wear and make it easier has the greatest significance. The ma- need to be modified based on prac- for the wedge-shaped cutting tool gnitude of the deformation energy and tical operating experience whenever to penetrate the workpiece materi- cutting energy dissipated during chip other factors have to be taken into al. For a given constant value of the formation depends on the tool rake. account. In such cases, it is important flank wear land VB, small increases in to know how a specific change in a the clearance angle will lengthen the When machining copper materials, the cutting angle will affect the machining service life of the cutting edge due to tool rake typically lies within the broad parameters. In view of the consid- the increased wear volume. Removing range 0° to 25°. When machining with erable progress that has been made a larger wear volume requires a longer a cemented carbide tool, the largest in the field of cutting tool materials, period of time so that the tool life in- rake angles are chosen for the softest modifying tool geometry in order to creases accordingly. However, a larger materials with the lowest cutting forces reduce tool wear is not so important clearance angle also means a weaker (pure copper, CuZn10) as these are the Abb. 6 Eingggriffsverhältnissetoday as it once was. The predomi- beimtool Läncutting tipg ands-Runddrehen this therefore only materials (()nach that do not DIN result in 6580) nant reason for altering tool angles is places a limit on the extent to which overloading of the cutting edge.

DirectionSchnittbewegung of primary motion / cutting direction(Werkstück) (workpiece)

ap κr: ToolEinste cuttingllwink edgee l angle a : DepthSchnitttiefe of cut b p f: FeedVorschub (here: distance travelled per revolution) κ r h b: Undeformed Spanungsbreite chip width a p h: Undeformed Spanungs di chipck e thickness b = sin κr a p ⋅ f = ⋅hb : AreaSpanungsquerschnitt of uncut chip

h = f ⋅sin κr DirectionVorschubbewe of feed motiongggung (Werkzeug)(tool)

Fig. 6: Geometry of tool engagement during cylindrical turning (oblique cutting con-figuration) (DIN 6580)

DKI Monograph i.18 | 7

© WZL/Fraunhofer IPT Seite 7 The larger the tool rake, the lower the chining copper-based materials, the copper alloys. In the case of work ma- deformation and cutting energy and smallest tool rakes are used for high- terials that are liable to smear, such as thus the lower the pressure exerted on strength copper alloys. Strong cutting soft copper or gunmetal, a tool cutting the cutting edge. The cutting forces are tools enable the workpiece to undergo edge angle of κr = 90° is preferred. On reduced accordingly and the tempera- high-speed turning. The disadvantage the other hand, if the depth of cut is ture of the cutting edge decreases. The is that as the rake angle is reduced, held constant, a reduction in the tool chip compression ratio is reduced and the cutting forces increase therefore cutting edge angle results in an increa- the quality of the machined surface raising the required machine power. se in the undeformed chip width b as improves accordingly. Large rake angles the stress is distributed over a longer facilitate chip flow when machining For a fixed depth of cut ap and a fixed portion of the cutting edge. The tool ductile copper materials, but they also tool feed f, the undeformed chip width life rises accordingly and this permits facilitate the formation of ribbon chips b and the undeformed chip thickness a slight increase in the cutting speeds. and tangled chips. h depend on the tool cutting edge The machining parameters listed in the angle κr (Fig. 6). If the tool cutting tables apply to large tool cutting edge The rake angle must be reduced if edge angle is too small (or equally if angles from about 70° to 90°. the specific cutting force is increased, the tool’s nose radius is too large), the or if the undeformed (i.e. uncut) passive forces will be greater, which The tool cutting edge inclination λs chip thickness is increased, or if the facilitates deformation and chattering (Fig. 5, Fig. 7) offers a simple means of transverse rupture strength of the tool if the work material being machined is stabilizing the cutting edge if the cut is material is lowered. This improves the weak. A large tool cutting edge angle interrupted, and of influencing chip stability of the cutting tool and reduces κr in the range 70° to 95° is typically flow. If the angle of inclination of the the risk of tool breakage. When ma- chosen when machining copper and tool cutting edge is negative, the first Abb. 7: Einfluss der Schneidengeometrie auf den Zerspansvorg ggang

Sharp Scharfkantigcutting edge (tool tip) increasingsteigende tool SchnittSection A – AA — > reducedgeringere tool stability Sc hne id ens ta bilität stabilitySc hne idens ta bilität A in the plane Po > smallkleine undeformed Sppganun gchipsdicken thickness in Po

γo = 00°° bitos 25° 25°

improvedbessere Ob surfaceer fläc hqualitye lowerverminderte cutting Schnittkräfte forces = 6° to 10° abnehmender Verschleiß ααoo= 6° bis 10° less wear chip Tool withmit Fbevelled ase cutting edge formsgegeb mayenen bef a llworses schl ec htere > greatererhöhte tool stabilitySchneidenstabilität Spanformen increasingsteigende > largergroße undeformed Spanungsdicken chip thickness less wear toolSchneiden - abnehmender stabilitystabilität Verschleiß

steigende lessabnehmender wear ViewAnsicht along Z Z in the κr better surface quality rε Ober fläc henqua lität Verschleiß planein P Pss lessvermindertes chatter Rattern decreasingsink end e P passiveassi vk r äfforceste lessvermindertes chatter Rattern decreasingsinkende Passivkräftepassive forces

guidedgelenkter chip flow Spanabl au f λs größere Passivkräfte larger passive forces steigende increasing tool stability Schneidteilstabilität

8 | DKI Monograph i.18 point of contact between the work- the cutting edge corner to withstand is too small, the corner of the cutting piece and the tool occurs above the stresses. The smaller the tool included edge will suffer premature damage. tool tip thus protecting the tip, which angle, the lower the mechanical load- Small corner radii are consequently is the most vulnerable part of the tool. ing that can be sustained by the cut- reserved for fine machining work. If As high impact loading of the cutting edge. In addition, heat generated the selected nose radius is too large, ting edge is unlikely when machining during machining is less well conduct- there is a tendency for the tool’s minor copper materials, λs is often set to 0°, ed away from the cutting edge corner cutting edge to scrape against surface particularly when only light machining so that the tool is exposed to greater of the workpiece creating notch wear of the workpiece is required. A nega- thermal stress. The tool included angle on the flank of the minor cutting edge tive tool cutting edge inclination is pre- should be as large as possible. For (see Fig. 8) that has a detrimental ferred for rough machining work and most machining operations on copper affect on the quality of the machined for interrupted cuts in high-strength materials εr is chosen to be 90°. How- workpiece surface. The optimal value copper alloys. A positive angle of ever, when machining a right-angled of the nose radius rε depends on the inclination improves chip flow across corner in the workpiece, a tool includ- undeformed chip thickness h and thus the tool face and is therefore preferred ed angle of less than 90° is required. on the feed displacement f. The nose when machining materials such as In many cases a compromise has to be radius rε should generally be between pure copper that show a propensity to found between the tool cutting edge 1.2 and 2 times the feed f; for copper adhere to the working surfaces or to angle and the tool included angle. rε should be chosen to be less than undergo strain hardening. 1.5·f. For soft copper materials, such as The size of the nose radius (also Cu-DHP, the machined surface quali- The tool included angle εr (Fig. 5 / Fig. known as the tool corner radius) rε ty is strongly dependent on the nose 7) is the angle between the major and (Fig. 5 / Fig. 7) should be selected for radius rε. When machining very ductile minor cutting edges. The size of εr has the particular machining operation materials, a small nose radius can a significant effect on the capacity of to be performed. If the nose radius improve cutting in the region of the

Flank wear land VB Verschleißmarkenbreite VB N KB: KB: cr Kolkbreiteater width α B B V V B KM: dist ance of centre of crater S C

KM: Kolkmittenabstand ax. B B V from tool edge rε m KT: Kolktiefe V

B b/4 KT: maximum crater depth SVα: Schneidenversatz in VB SVα: FlRichtungank-side Freifläche displacement of C B A N SVγ:cuttingSchneidenversatz edge in SV : FRichtungace-side Spanflächedisplacement of NotchVerschleißkerbe wear on major γ b an der cutting edge cuttingHauptschneideHauptsc edgehneide SchnittSection AA- A— A NotchVerschlei wearßkerben on minor an dercutting Nebenschneide edge

CraterKolk

A PlaneEbene P Ps s (ISONach: 3685) ISO 3685:93

Fig. 8: Types of wear and wear parameters on turning tools (ISO 3685)

DKI Monograph i.18 | 9 minor cutting edge. This is because the 2.2 Tool wear primarily the wear on the tool’s flank larger minimum thickness of cut means During the machining process, wear and face that are used as the criteria that the material can be cut more marks will appear on the tool. The for assessing tool life. The wear that easily and does not therefore tend extent of tool wear will depend on the develops on the tool’s flank is known as to smear so much. This reduces the stresses to which the tool is subject- flank wear land (VB). A tool is deemed roughness and improves the quality of ed. Wear marks appear on the major to be worn and therefore at the end of the cut surface. As a rule, if the feed and minor flanks of the cutting tool its useful service life if the flank wear is held constant, a larger nose radius where it is contact with the workpiece, land VB has reached a specified width will lead to the formation of shal- and on the tool face where it is in (Fig. 8). The width of the permissible lower and less pronounced feed marks contact with the chip being removed. flank wear land depends on the specific on the workpiece. The kinematic As a rule, the greater the amount of workpiece requirements. roughness is reduced and the quality wear, the greater the mechanical and A large flank wear land VB results in of the workpiece surface, expressed by thermal stress experienced by the tool. a large face-side displacement of the the two surface parameters Ra and Rz, Tempering in the tool material, which cutting edge SVγ causing dimensional is improved. This effect is used in tools occurs in tool steel at about 300 °C and inaccuracies. Furthermore, the greater with so-called wiper geometry. A wiper in high-speed steel at around 600 °C, area of frictional contact between the nose radius insert features additional causes a loss in tool hardness and can tool and the workpiece results in a de- larger radii that are located along result in the sudden tool failure as a terioration in the quality of the work- the minor cutting edge behind the result of so-called ‘bright braking’. piece surface and an increase in cut- tool nose. Compared to inserts with a In the case of tool inserts made of ting temperature. When machining on conventional nose radius, wiper inserts cemented carbide, which at 1000 °C still an automatic lathe, the maximum per- can produce an improved surface finish exhibits the same hardness that high- missible width of the flank wear land with the same feed, or the same sur- speed steel does at room temperature, is 0.2 mm if cemented carbide tools are face quality at higher feeds [5]. the wear is predominantly abrasive in used, for rough machining the width nature. In practical applications, it is of the flank wear land should not ex-

StructuringStruktur in im workpiece Werkstück

Shear v Scher- c plane ebene StructuringStruktur withinim Span chip 5 1 3

2 4

FlankFreifläche SpanflächeFace

Cut surface of ToolWkWerkzeug Scworkpiecehni ttfl äch e TurningDrehmeißel tool 1.1 Primary primäre shear Scherzone zone 2.2 Secondary sekundäre shear Scherzone zone on the an tool der rake Spanfläche face 3.3 Se sekundärecondary shear Scherzone zone at the an stagnation der Stau- and und separation Trennzone zone Material:Werkstoff: Cu-ETPCu-ETP 4. Secondary shear zone on the flank face Cutting speed: vc = 80 m/min 4 sekun däre Sc herzone an der Fre ifläc he Sc hn ittgesc hw in dig ke it: vc = 80 m /m in 5.5 Elastic-plasticVfVerformungsvor deformation lau fzone zone FeedVorsc per hbh urevolution:b: f = 0,02f =mm 0 ,02 mm

Fig. 9: Material deformation zones during chip formation (Source: [6])

10 | DKI Monograph i.18 ceed a value between 0.4 and 0.6 mm, The details of chip formation process zones (see Fig. 9). These shear stresses depending on the diameter of the part can be most readily seen using the or- cause plastic deformation in the sec- being made, the specified tolerances thogonal cutting model. In the ortho- ondary shear zones thereby compress- and the required surface quality (Fig. gonal model, chip formation is consid- ing the chip. The result of this defor- 8). Wear land widths of 1 mm or more ered to occur as a two-dimensional mation is that the thickness of the chip can arise during heavy roughing work process in a plane perpendicular to the after separation hch is greater than the involving feeds rates of 1.0 to 1.8 mm/ cutting edge, as depicted photograph- original thickness of cut h (= thick- rev and cutting depths of 10–20 mm. ically and schematically in Fig. 9. ness of the undeformed chip), and the The wear on the tool’s rake face (Fig. 8) width of the chip bch is greater than is generally less significant than the During the machining process, the cut- the original width of cut b (= width of wear on the flank and is expressed in ting tool penetrates the work material, the undeformed chip): terms of the crater ratio K = KT/KM. K which deforms first elastically and then is a measure of the weakening of the plastically. As soon as the shear stress cutting tool as a result of cratering on induced by the tool reaches or exceeds the rake face and should never signif- the shear strength of the work material Chip thickness icantly exceed a value K = 0.1. in the shear zone, the material begins compression: (2) to flow. Depending on the tool geometry used, the deformed work material Chip width b 2.3 Chip formation forms a chip that flows across the face compression: ch > 1 (3) Abb. 10:SpanartenChip formationin Abhän and effectiveggg chipig keitof thevon cutting tool.den Werkstoffeigenschaften b [[]VIER70] removal are important in those cutting techniques in which the cutting zone Friction between the contact planes of is spatially limited, such as drilling, the tool and the underside of the chip Four main types of chip can be formed: reaming, milling and all turning oper- or the new workpiece surface creates continuous chips, continuous segment- ations on automatic lathes. shear stresses in the secondary shear ed chips, semi-continuous segmented

(2) Continuous segmented (3) Semi-continuous segmented (1) Continuous chip 1 Fließspan 2(or serrated)Lamellenspan chip 3(or serrated)Scherspan chip

elastischerelastic zone FormationLamellen- ,of Scher segmen- und Fließspan- Formation of con- plastischeplastic zoner tedReißspanbereich or discontinuous bereich (4) DiscontinuousReißspan chip tinuous chips Fließbereich 4 chips

τ flow zone it it e igk

t 1 B

rfes 2 EZ Shear strength Shear che

S 3 4 ε

ε0 εο VfVDegreeerformungsgra of deformationd in the DegreeVerformungsgrad of deformation ε inshear der planeScherebene

Fig. 10: Influence of mechanical properties of workpiece material on type of chip formed (Source: [7])

DKI Monograph i.18 | 11

© WZL/Fraunhofer IPT Seite 11 chips and discontinuous chips of chip sections that were completely built-up edge may periodically break (see Fig. 10). separated in the shear zone. This type off and become deposited between of chip forms when the degree of the tool flank and the surface of the Continuous chips form when the mate- deformation in the shear zone exceeds workpiece, or may become dislodged rial being cut flows away continuously the material’s ductility. This applies with the chip. As a result the quality from the machining point. The regions not only to brittle materials, but also of the workpiece surface deteriorates, of deformed material undergo lamel- to materials in which the deformation tool wear increases, the dimensional lar sliding but without exceeding the induces brittleness in the microstruct- accuracy of the machined workpiece shear strength of the material. ure. Semi-continuous segmented worsens and the relative percentage of chips can also form at extremely low dynamic cutting forces rises. If the work material being machined is cutting speeds. Discontinuous chips of sufficient ductility, the chip formed typically form when brittle materials The occurrence of built-up edges is will usually be continuous in form, with an inhomogeneous microstructure temperature dependent. When copper provided that the cutting process is not are machined. These chips are not cut and materials with a high copper impaired by the influence of external but rather torn from the surface of the content are machined, BUE formation vibrations. work material, with the result that the always occurs in a specific range of workpiece surface is frequently damag- the cutting speed vc and the thickness If the workpiece material is of lower ed by these small chip fragments. of cut h. BUE formation also depends ductility, if it has an inhomogeneous on the tool’s angle of rake. To avoid microstructure or if it is subjected to Machining highly ductile materials, the formation of a built-up edge, external vibrations, machining will such as Cu-ETP or Cu-DHP, at low the machine operator can select a result in the formation of continuous cutting speeds can lead to the forma- greater thickness of cut h, can raise the segmented (or serrated) chips. tion of a so-called built-up edge (BUE) cutting speed vc and/or can increase Compared with continuous chips, the on the tool’s cutting edge and rake the rake angle γ. If that is not possi- upper surface of the chip in this case face. A built-up edge is made up of ble, vc should be reduced to below the exhibits a pronounced sawtooth-like strain-hardened layers of the work- lower limit for BUE formation (e.g. in structure. Continuous segmented (or piece material that adhere around the reaming, tapping). In the latter case, serrated) chips can form at high feed cutting edge, giving the cutting edge it is important to reduce friction at the rates and at high cutting speeds. an irregular shape and preventing the cutting interface by achieving the best chip from coming into direct contact possible cooling lubrication of the tool. Semi-continuous segmented (or serrat- with the tool. Depending on the speed) chips, on the other hand, consist cific cutting conditions employed, the

12 | DKI Monograph i.18 3 Machinability

There is no unique or unambiguous cutting zone than short spiral chips, formation. The emphasis in finishing definition of the term ‘machinability’. chip curls or discontinuous chips. work, in contrast, is primarily on the It can be understood as summarizing These longer chips can form tangled quality of the final surface, with chip those properties of a material that balls within the machine, resulting shape and chip formation playing a determine the ease or difficulty with in the interruption of the machining secondary role. However, when ma- which that material can be machined process and damage to the workpiece chining on an automatic lathe, chip by various machining operations or and tool. They are also a safety hazard shape and chip formation may be the techniques. The machinability of a to the machine operator. In most sole criterion used to assess the ma- material can vary very strongly de- cases, ribbon chips and tangled chips chinability of a workpiece material. pending on the geometry and material have to be removed manually from of the cutting tool, the machine tool the workpiece or cutting tool, which and machining technique used and introduces machine downtimes thus 3.1 Tool life the machining conditions. The main lowering productivity. As ribbon and The tool life T is defined as the time goal of any machining operation is the continuous chips have a tendency to in minutes during which a cutting fabrication of a workpiece of the deform snarled and tangled balls, their tool performs a machining operation sired geometry. In view of the complex formation should, wherever possible, under specified cutting conditions relationships between the numerous be avoided. But fine needle-like chips from the start of the cut to the point at factors involved, it is not possible to can also cause problems as they can which the tool has become unusable assess machining operations in terms block cutting fluid filters or get under by reaching a predetermined tool-life of one single standardized machining the machine housing where they can criterion. criterion. cause increased wear. The tool life depends on numerous We will assess the machinability of The forces generated in metal cut- factors, including: copper and copper alloys in terms of ting operations determine the power the following four machining crite- requirements and the structural ● the material to be machined, ria: tool wear; chip formation; cutting rigidity of the machine tool. They have forces and surface quality. Although a considerable influence on tool wear ● the tool material, these four quantities are mutually and therefore on tool life. Generally interdependent, the additional influ- speaking, the harder a material is to ● the cutting speed, the feed and the ence of factors such as the condition machine, the greater the forces that depth of cut, of the workpiece material, the cutting have to be applied. Cutting forces operation, the specifics of the machine tend to decrease in magnitude with ● the cutting tool geometry, tool and cutting tool used and the role increasing cutting speed, because at of lubricants and cooling fluids, means higher cutting speeds, the cutting ● the quality of the cutting edge that it is not possible to create a single temperature is greater, which in turn (‘tool finish’), unambiguous machinability criterion. results in a reduction in material strength (so-called thermal softening). ● the vibrations and motional ac- Tool wear is understood to mean The cutting force components increase curacy of the workpiece, tool and the progressive loss of material from proportionally with increasing depth of machining equipment, the surface of the cutting tool. The cut and also increase with feed though processes that cause tool wear during the rate of increase is less pronounced ● the tool-life criterion, i.e. the machining are abrasion, adhesion, at higher feeds. threshold value of tool wear, typi- scale from high-temperature oxida- cally expressed as the width of the tion, diffusion, thermal and mechanical High dimensional accuracy and good flank wear land VB. stresses and surface fatigue. surface quality are frequently required when machining copper and copper The cutting speed has the strongest in- Chip formation and chip shape play an alloys. The resulting quality of the fluence on tool wear. The effect of feed extremely significant role in determin- machined workpiece surface (rough- on tool wear and thus on tool life is ing efficient chip removal, process ness) is very often the most important also significant. The depth of cut also safety and high productivity. This is machining criterion. influences tool wear, but the effect is particularly true for those machining very minor in comparison. operations in which the cutting zone The relative weighting of the four main is of limited size. This is the case for machinability criteria mentioned above The dependence of the tool life on machining techniques with restricted will depend on the goal of the particu- cutting speed can be represented in a chip flow, e.g. drilling, tapping, plunge lar machining operation being used. tool-life graph. The tool-life graph is a cutting, broaching, grooving and all For example, in rough machining work, log-log plot with cutting speed data vc cutting and shaping operations on CNC the machinability criterion of greatest (in m/min) plotted on the abscissa and machines. Long ribbon and tubular relevance is tool wear, followed by the corresponding tool life T (in min) chips are harder to remove from the cutting forces, chip shape and chip plotted on the ordinate (see Fig. 11).

DKI Monograph i.18 | 13 33 Der Der Begriff Begriff Zerspanbarkeit Zerspanbarkeit 17 17

aufgetragen,aufgetragen, Abb. Abb. 11. 11. Die Die sich sich ergebende ergebende Kurve Kurve lässt lässt sich sich über über eineneinen großen großen Bereich Bereich durch durch eineeine Gerade,Gerade, diedie .sogenannte.sogenannte Standzeit-GeradeStandzeit-Gerade oderoder „Taylor-Gerade“„Taylor-Gerade“ annähern,annähern, diedie sichsich ausgehendausgehend von von der der Geradengleichung Geradengleichung

yy==mmxx++nn (4)(4)

unterunter Berücksichtigung Berücksichtigung der der doppeltlogarithmischen doppeltlogarithmischen Darstellung Darstellung wie wie folgt folgt darstellt: darstellt:

logT = logC + k logv logT = logCvv+ k logvcc (5)(5)

NachNach dem dem Entlogarithmieren Entlogarithmieren ergibt ergibt sich sich dann dann die die sog. sog. "Taylor-Gleichung” "Taylor-Gleichung” 3 Der Begriff Zerspanbarkeit 17 3 Der Begriff Zerspanbarkeit T = v kk C 17 T = vcc Cvv (6)(6) aufgetragen, Abb. 11. Die sich ergebende Kurve lässt sich über einen großen Bereich durch aufgetragen, Abb. 11. Die sichAs can ergebende be seenDarinDarin in bedeuten: Fig. bedeuten:Kurve 11, the lässt resulting sich T: T: die dieüber Standzeit Standzeit k:einen Gradient großen in in ofmin min the Bereich straight linedurch in the life curve, is of particular relevance to eine Gerade, die .sogenanntecurve canStandzeit-Gerade be approximated overoder a large„Taylor-Gerade“ tool-life annähern,plot (k = tan dieα) sich practical applications as it expresses eine Gerade, die .sogenannte Standzeit-Gerade oder „Taylor-Gerade“ vc: die Schnittgeschwindigkeit annähern, die in sichm/min part of the plot as a straight line with vc: die Schnittgeschwindigkeit in m/min how the tool life T varies as a function ausgehend von der Geradengleichung the standard straight line equationk:k: die die Steigung Steigung Cv: Tool lifeder der T Geraden forGeraden unit cutting im im Standzeitdiagramm Standzeitdiagrammspeed of the cutting (k (k speed= = tan tan v c.) )The steeper C : die Standzeit(vc = 1 m/min.) T für v = 1 m/min. the gradient of the tool life plot, i.e. y = m x + n Cv:v die Standzeit T für vc c= 1 m/min. y = m x + n (4) (4) the smaller the angle of inclination The Taylor equation can be rearranged α, the greater the dependence of tool As the plotDurch Durchis a log-log Umstellen Umstellen representation, der der Taylor-Gleichung Taylor-Gleichung to yield: ergibt ergibt sich sich life on cutting speed. At low cutting unter Berücksichtigung der thisdoppeltlogarithmischen equations becomes: Darstellung wie folgt darstellt: speeds, the relationship between log unter Berücksichtigung der doppeltlogarithmischen Darstellung wie folgt11 darstellt: v = Tkk C (6a) T and log vc is no longer linear due to vcc= T CTT (6a)(6a) built-up edge formation at the cutting logT = logCv + k logvc (5) logT = logCv + k logvc (5) log logdabeidabeiv ist ist log c where(5) tool edge. Taking the antilogarithms to transform 11 back to the original variables generates C = C kk While the Taylor equation is completely Nach dem Entlogarithmieren ergibt sich dann die sog. "Taylor-Gleichung”CTT = C (7) (7)(7) Nach dem Entlogarithmierenthe ergibt so-called sich Taylor dann equation: die sog. "Taylor-Gleichung” adequate for most practical appli- C , C and k are quantities that charac- cations, this simple-to-use tool-life k CT, Cv und k sind kennzeichnendeT v Größen der Schnittbedingungen, die sich mit dem Werk- T v k CT, Cv und k sind kennzeichnende Größen der Schnittbedingungen, die sich mit dem Werk- T = vc Cv terize(6) the cutting conditions and that relationship does not have general va- T = vc Cv (6) (6) Abb. 11: Standzeit-Schnittgeschwindigkeits-Diagrammstoff,stoff, demdem Schneidstoff,Schneidstoff, derdervary Schneidkeilgeometrie, Schneidkeilgeometrie,depending on the work material, im demdem doppeltlogarithmischen Spanungsquerschnitt Spanungsquerschnittlidity. For example, milling undund dessenoperationsdessen Darin bedeuten: T: die Standzeitwhere: Aufteilung Aufteilungin min inin VorschubVorschub undundthe SchnitttiefeSchnitttiefe cutting tool geometryusw.usw. ändernändern and the (nach(nach VDIVDItend RichtlinieRichtlinie to exhibit 3321). tool-life3321). Der Derrelationships Expo-Expo- Darin bedeuten: T: die Standzeit T: Tool life in in min minutes area of the undeformed (i.e. uncut) that cannot usually be approximated vc: die Schnittgeschwindigkeitnentnent k, k, das das Maß Maß in derm/minder Steigung Steigung der der Geraden, Geraden, ist ist besonders besonders wichtig wichtig für für die die Praxis. Praxis. Er Er drückt drückt die die Syyystem mit Standzeit vc: diebzw. Schnittgeschwindigkeit Taylor-Geraden in m/min chip, which is itself determined by by the Taylor expression. vc: CuttingVeränderungen speed in metres per der Standzeitthe chosen in Abhängigkeit feed and depth von of cut der (cf. Schnittgeschwindigkeit vc aus. Je k: die Steigung Veränderungender Geraden im derStandzeitdiagramm Standzeit in Abhängigkeit (k = tan ) von der Schnittgeschwindigkeit vc aus. Je k: die Steigungminute der Geraden im StandzeitdiagrammVDI Guideline (k 3321).= tan The ) exponent k, To deal with these cases, so-called Cv: die Standzeitgrößergrößer T für vdiediec = Neigung1Neigung m/min. derder GeradenGeraden ist,ist, alsoalso jeje kleinerkleiner derder NeigungswinkelNeigungswinkel ist,ist, destodesto mehrmehr ver-ver- Cv: die Standzeit T für vc = 1 m/min. which determines the slope of the tool extended Taylor equations have been ändert sich die Standzeit mit der Schnittgeschwindigkeit. Bei developedniedrigen that Schnittgeschwindig- take into account other ändert sich die Standzeit mit der Schnittgeschwindigkeit. Bei niedrigen Schnittgeschwindig- variables that can influence tool life. Durch Umstellen der Taylor-Gleichungkeitenkeiten ergibt wirdwird sich derder geradlinigegeradlinige VerlaufVerlauf derder StandzeitbeziehungStandzeitbeziehung dadurchdadurch gestört,gestört, dassdass sichsich Auf-Auf- Durch Umstellen der Taylor-Gleichung ergibt sich One example is the extended Taylor 1 1 bauschneiden100 an der Werkzeugschneide bilden. v T k bauschneidenC an der Werkzeugschneide bilden. equation that has been modified to vc = T k CT (6a) vc = T CT (6a) account for the effects of feed and 3 Der Begriff Zerspanbarkeit depth of cut: 18 dabei ist FürFür die die BelangeBelange der der Praxis Praxis ist ist die die einfache einfache Taylor-Gleichung Taylor-Gleichung meist meist völlig völlig ausreichend. ausreichend. Diese Diese 1 1 k recht einfach zu handhabende Standzeitbeziehung besitzt allerdings keine allgemeine Gül- C C krecht einfach zu handhabende αStandzeitbeziehung besitzt allerdings keine allgemeine Gül- CT = C k (7) C1 T = tigkeit. So werden z.B. beim(7) Fräsen Standzeitbeziehungen gefunden,T = die sich nur (8)in Aus- (8) tigkeit. So werden z.B. beim Fräsen Standzeitbeziehungen gefunden,ca diec fsich knur in Aus- ap f vc CT, Cv und k sind kennzeichnende Größennahmefällen der Schnittbedingungen, mit „Taylor“ annähern die lassen. sich mit dem Werk- CT, Cv und k sind kennzeichnende nahmefällenGrößen der Schnittbedingungen,mit „Taylor“ annähern die lassen. sich mit dem Werk- where: stoff, dem Schneidstoff, der Schneidkeilgeometrie, dem SpanungsquerschnittMit: und dessenT Werkzeugstandzeit in min in T Tool life in minutes Aufteilung in Vorschub und SchnitttiefeEsEs gibtgibt usw. daherdaher ändern nochnoch (nach diedie sog. sog.VDI erweitertenerweitertenRichtlinie = 3321). αTaylor-Gleichungen,Taylor-Gleichungen, Der Expo-v Schnittgeschwindigkeitdiedie weitereweitere diedie StandzeitStandzeit in m/min eineseines Aufteilung in Vorschub und Schnitttiefem usw. ändern (nach VDI Richtliniek tan 3321). Der Expo-c [min] [min] nent k, das Maß der Steigung der Geraden,WerkzeugesWerkzeuges/ ist besonders beeinflussendebeeinflussende wichtig GrößenfürGrößen die Praxis. berücksichtigen.berücksichtigen. Er drückt f die EinEin BeispielBeispiel Vorschub v C uttinghierfürhierfür (pro speed Umdrehungistist indiedie metres denden per Vor-)Vor- in mm nent k, das Maß der Steigung der Geraden,T ist besonders wichtig für die Praxis. Er drückt die c 10 ap Schnitttiefe in mm

it minute Veränderungen der Standzeit in Abhängigkeitschubschub und und die die von Schni Schni dertttiefetttiefe Schnittgeschwindigkeit enthaltende enthaltende erweiterte erweiterte vc Taylor-Gleichung aus.Taylor-Gleichung Je Veränderungen der Standzeit in Abhängigkeite von der Schnittgeschwindigkeit vc aus.k Je die Steigung der Geraden im Standzeitdiagramm (k = tan )

größer die Neigung der Geraden ist, dz also je kleiner der Neigungswinkel ist, desto mehr ver- größer die Neigung der Geraden ist, also je kleiner der Neigungswinkel ist, desto mehr Cver-1 dimensionsbehaftete, f Feed in mm per revolution empirisch ermittelte Konstante n C dimensionslose Konstante: Exponent der Schnitttiefe ändert sich die Standzeit mit der Schnittgeschwindigkeit.ta Bei niedrigen Schnittgeschwindig-a ändert sich die Standzeit mit der Schnittgeschwindigkeit.T [min] life Tool Bei niedrigen Schnittgeschwindig-

S a Depth of cut in mm keiten wird der geradlinige Verlauf der Standzeitbeziehung dadurch gestört,LinearStandzeitgerade tool-life dass sich function CAuf-f dimensionslosep Konstante: Exponent des Vorschubs keiten wird der geradlinige Verlauf der Standzeitbeziehung dadurch gestört, dass sich Auf- k Gradient of the straight line in bauschneiden an der Werkzeugschneide bilden. Den Einflüssen entsprechend ist derthe Exponent tool-life plot k (krelativ = tan groß,α) während Ca und insbesondere

Für die Belange der Praxis ist die einfache Taylor-Gleichung meist völligCf nur ausreichend. kleine Werte Diese annehmen. In der Zahlenwertgleichung ist C1 eine dimensionsbehaftete Für die Belange der Praxis ist die einfache Taylor-Gleichung meist völlig ausreichend. Diese C1 Dimensioned, empirically Konstante, die von Werkstoff, Schneidstoffdetermined und constant Zerspanungsverfahren abhängt. recht einfach zu handhabende Standzeitbeziehung besitzt allerdings keine allgemeine Gül- tigkeit. So werden z.B. beim Fräsen Standzeitbeziehungen1 gefunden, die sich nur in Aus- C Dimensionless constant: the 10 C 100 a nahmefällen mit „Taylor“ annähern lassen. T exponent of the depth of cut

Sc hn ittgesc hw in dig ke it 100 Cf Dimensionless constant: the Es gibt daher noch die sog. erweiterten Taylor-Gleichungen,Cutting speed[m/min] die v cweitere [m/min] die Standzeit eines Es gibt daher noch die sog. erweiterten Taylor-Gleichungen,vc / (m/min) die weitere die Standzeit eines exponent of the feed Werkzeuges beeinflussende Größen berücksichtigen. Ein Beispiel hierfür ist die den Vor- The size of the parameters k, C and C schub und die Schnitttiefe enthaltende erweiterte Taylor-Gleichung a f schub und die Schnitttiefe enthaltendeFig. 11: Taylor tool-life erweiterte diagram Taylor-Gleichung (log-log plot of tool life against cutting speed) reflect the strength of their influence © WZL/Fraunhofer IPT Seite 12 14 | DKI Monograph i.18

10 Standzeit T / min Standzeitgerade

1 10 C 100 T k tan Schnittgeschwindigkeit= v / (m/min) c

Abb. 11: Standzeit-Schnittgeschwindigkeits-Diagramm im doppeltlogarithmischen System mit Standzeit bzw. Taylor-Geraden 3 Der Begriff Zerspanbarkeit 19

3.2 Zerspankraft

Zur Beurteilung der Zerspanbarkeit eines Werkstoffs wird als weitere Kenngröße die entste- hende Zerspankraft herangezogen. Die Kenntnis der Zerspankräfte ist Grundlage für die on tool life; the exponent −k is rela- chinery. To determine the drive power where: tively large,Werkzeugmaschinen-, whereas Ca and particularly die Werkzeug-requirements undor to diedimension Vorrichtungs-Konstruktion. a tool Fc Cutting Außerdem force in N erlaubt Cf assume dieonly Kenntnis small values. der C 1Zerspankräfte, is a holding anfallende system it is Zerspanaufgaben generally suffi- leistungsgerecht auf vorhande- dimensioned constant that depends on cient to make a rough estimate of the b Chip width in mm the workpiecene Werkzeugmaschinenmaterial, the tool mate- zuexpected verteilen. cutting Dabei forces. genügt für den Betrieb im Allgemeinen eine rial and theüberschlägige cutting operation. Abschätzung der Zerspankräfte, um z. B. die erforderliche h Undeformed Leistung chip zu thicknesserrech- As shown in Fig. 12, the total cutting in mm nen oder das Werkzeugspannforcesystem F can be zu resolved dimensio intonieren. three 3.2 Cutting force components: the cutting force Fc, the mc Dimensionless index reflecting The cuttingDie force Zerspankraft generated at theF kann, wiefeed in forceAbb. F f12 and dargestellt, the passive forcein drei (or Komponententhe –increase in die ofSchnittkraft the specific tool’s cutting edge is a further para- back force) Fp. The symbols used here cutting force meter usedF cto, diecharacterize Vorschubkraft the ma- Ff undto die designate Passivkraft the force Fp components – zerlegt werden.are Die Bezeichnung der Kraft- chinabilitykomponenten of a material. An erfolgt under- dabei thosenach found der DINin the 6584 DIN 6584 „Begriffe standard. der Zerspantechnik 1-mc Gradient –of Kräfte,the straight Ener- line standing of the cutting forces acting is The required drive power is determi- F ' = f(h) in a log-log plot gie, Arbeit, Leistungen“. Die für die Zerspanung erforderliche Maschinenleistungc wird maß- fundamental to the design of machine ned primarily by the cutting force Fc. 2 tools, cuttinggeblich tools anddurch tool die holders Schnittkraft According Fc beeinflusst. to Kienzle and Nach Victor, Kienzle the und Victorkc1.1 Spelässtcific sich cutting die force Schnitt- in N/mm and workpiece holders. Knowledge of cutting force F can be calculated as for b = h = 1 mm kraft Fc wie folgt berechnen: c the cutting forces also enables machin- follows: ()1−m ing jobs to be intelligently distributed The term c is expressed in mm. ()1m h among the available production ma- F = k b h c (9) Corresponding equations can be de- Abb. 12: Zerlegggung der Zers pankraft (nach DINc 6584)c1.1 (9) fined for the other two force com- Direction of primary ponents Ff and Fp. Mit: ve Fc Schnittkraftvcc:: CuttingShittSc hinnitt N gescspeed h w idikitindigkeit vc motion / vff: FeedVorschubgeschwindigkeit speed Scuttingbc h n ittb directionewegung Spanungsbreite in mm € v :: Effective Wirkgggeschwindi cutting speedgkeit The graphical determination of the spe- (workpiece)h (Werkstück) Spanungsdickeee in mm cific cutting force kc1.1 or the material-de- m dimensionsloser Anstiegswert der spezifischen Schnittkraft c F:F :Total Zerspankra cutting forceft pendent factors mc or (1-mc) is illustrated

1-mc SteigungFcc :: CuttingSchnittkraftder forceGeraden Fc' = f(h)in Fig.im 13doppeltlogarithmischen and described in detail in the Ff F : Feed force vf System Fff: Vorschubkraft literature [8, 9, 10]. The cutting force 2 Fpp:: Passive Passivkraft force Fp kc1.1 spezifische Schnittkraft in N/mm fürexpressions b = h = given 1 mm above use only a Faa:: Active Aktivkraft force limited set of parameters. Other factors ()m1 h c FDD:: ThrustDrang force kra ft wobei mit der Dimension mm einzusetzen ist. Für die thatZerspankraftkomponenten influence the cutting force, such F asf Fc Fa the angle of rake γ, the cutting velocity vc, und Fp lassen sich entsprechende Gleichung definieren. tool wear and workpiece shape were

FD excluded for reasons of simplicity. Die graphische BestimmungF der spezifischen Schnittkraft kc1.1 bzw.Extended der versions werkstoffabhängigen of the Victor-Kienzle Abb. 13: Graphische Ermittlung der Kennwerte ki1.1 und (1-mc)f) mit i = c, f oder p DirectionVorschubbewe of feed gggmotionung equations are available in which these Faktoren(tool) m oder (1-m ) entsprechend Abb. 13 ist in der Literatur [VICT72, VICT69, KIEN52] [[]VICT72] (Werkzeug) c c additional parameters are included as

© WZL/Fraunhofer IPTdetailliert beschrieben. Neben den direkt in das SpankraftgesetzSeite 13 correction eingehenden factors. Parametern Fig. 12: Total cutting force resolved into component forces (DIN 6584) müssen aus Gründen der Übersichtlichkeit weitere Einflussgrößen wie Spanwinkel , In turning operations using carbide tools, Schnittgeschwindigkeit vc, Werkzeugverschleiß und Werkstückformthe only unberücksichtigt parameters in addition bleiben to the bzw. werden in den sog. erweiterten Victor-Kienzle-Gleichungenundeformed durch chip Korrekturfaktoren thickness h that have 1000 any practical influence the specific cutting berücksichtigt. 2 ) ki1. 1 = 947 N/mm force are the angle of rake γ, the angle m 800 of inclination and the degree of tool m mi λs

(N/ wear. It is generally the case that as the [N/mm] Beim Drehen mit Hartmetall haben neben der Spanungsdicke h praktisch nur der Spanwinkel ’ ’ /

i 600 i angle of rake γ increases, i.e. becomes F = F = , der Neigungswinkel s und der Werkzeugverschleiß1 Einflussmore auf positive, die Größe the specific der cutting spezifi- force kc b i i decreases by 1.5 % for every one degree te 1 - mi = 0,7265 F schen Schnittkraft. Man rechnet bei zunehmendem Spanwinkel bzw. Neigungswinkel s mit 400 rei ft change in angle. This statement is valid a b α einer Abnahme der spezifischen45º Schnittkraft kc von 1,5 % je Grad Abnahme in einem zuläs-

gs for the range of angles given by ±10 % tkr t n ± of the angle of rake originally measured. nu hni sigen Bereich von 10 % des ursprünglich der Messung zugrunde liegenden Span- bzw.

a 1 p Cutting force F Cutting force

Sc Tool wear plays a more significant role. 1−m

S i Neigungswinkels.F = kii 1.1 ⋅b⋅h Größereni=ci = c, f, p Einfluss hat der Verschleiß. Eine quantitativeHowever, in view Aussage of the numerous über den factors 200

Undeformed chip width b width chip Undeformed influencing the magnitude of the cutting Kraftanstieg0,1 mit0,2 zunehmendem0,4 Werkzeugverschleiß0,6 0,8 1,0 2,0ist wegen der Vielzahl an Einflussgrö- force, it is only possible to make appro- ßen nur näherungsweiseUndeformedSpanungsdicke chipmöglich. thickness h Als / mm h [mm]Anhaltswerte für den Kraftanstiegximate, semi-quantitative bis zum Erreichen statements about the increase in the cutting force

Fig. 13: Graphical determination of the parameters ki1.1 and (1-mc) with i = c, f or p [8] with progressive tool wear. It has been

ε DKI Monograph i.18 | 15 © WZL/Fraunhofer IPT Seite 14 Machinability Material Principal va- Gradient Notes on group lue of specific 1-mc experimental cutting force conditions 2 Designation EN number UNS number kC1.1 [N/mm ] (see Table 2) I CuSP CW114C C14700 820 0,93 1) CuTeP CW118C C14500 910 0,88 1) CuTeP CW118C C14500 544 0,7755 8) CuZn35Pb2 CW601N C34200 835 0,85 4) CuZn39Pb3 CW614N C38500 450 0,68 1) CuZn39Pb3 CW614N C38500 389 0,69 8) CuZn40Pb2 CW617N C37700 500 0,68 1) CuSn4Zn4Pb4 CW456K C54400 758 0,91 8) CuSn5Zn5Pb5-C CC491K C83600 756 0,86 6) CuSn7Zn4Pb7-C CC493K C93200 1400 0,76 7) CuSn5Zn5Pb2-C CC499K – 756 0,86 6) CuSn5Zn5Pb2-C CC499K – 724 0,82 8) CuNi7Zn39Pb3Mn2 CW400J – 459 0,70 8) II CuNi18Zn19Pb1 CW408J C76300 1120 0,94 1) CuZn35Ni3Mn2AlPb CW710R – 1030 0,82 1) CuZn37Mn3Al2PbSi CW713R – 470 0,53 3) CuZn38Mn1Al CW716R – 422 0,62 5) CuAl10Fe5Ni5-C CC333G C95500 1065 0,71 6) CuSn12Ni2-C CC484K C91700 940 0,71 6) CuZn33Pb2-C CC750S – 470 0,53 3) CuZn40 CW509L C28000 802 0,80 8) CuAg0,10 CW013A C11600 1100 0,61 2) CuNi1Pb1P – C19160 696 0,8095 8) III CuNi2Si CW111C C64700 1120 0,81 1) CuAl8Fe3 CW303G C61400 970 0,82 1) CuAl10Ni5Fe4 CW307G C63000 1300 0,88 1) CuSn8 CW453K C52100 1180 0,90 1) CuSn8P CW459K – 1131 0,88 8) CuZn37 CW508L C27400 1180 0,85 1) CuZn20Al2As CW702R C68700 470 0,53 3) CuMn20 – – 1090 0,81 8)

The mechanical properties of the wrought alloys listed in the following tables refer mainly to rods and bars (as defined in EN 12164, EN 12163, EN 13601 and EN 12166, strip (as in EN 1652 and EN 1654) and tubes (as in EN 12449). The values for the cast alloys are from EN 1982. The order in which the alloy groups are presented follows CEN/TS 13388.

Table 1: Specific cutting forces kc1.1 and gradient factors 1-mc for copper and copper alloys. (Note: data drawn from a variety of sources.) estimated that a flank wear land width The data in the table have been drawn the effect of the nose radius rε can be (VB) of 0.5 mm indicates that the cutting from numerous sources and cover a range ignored, a tool cutting edge angle of force will have increased by about 20 %, of different test conditions. κr = 90° means that the feed force Ff the feed force by about 90 % and the will be little more than 30 % of Fc. passive force by approximately 100 %. In some cases, the two other force components, the feed force Ff and the passive As the forces acting when copper The cutting force Fc can be calculated force Fp (Fig. 12) may also be of interest. materials are machined are generally using Equation 9 and the kc1.1 values that quite low, the following relationship is are listed in Table 1 . If a material is not The latter two forces are much smaller suitable for most approximate calcula- listed in Table 1, it is usually acceptable than the cutting force Fc. The passive force tions: for rough calculations to estimate the kc1.1 Fp does not do any work that would need values by adopting the values listed for a to be supplied by machine power as it is Ff ≈ 0,3 Fc (10) comparable material. orthogonal to the two main directions of motion (direction of primary motion and When turning with cemented carbide Table 2 contains information on the the direction of feed). tools at the now typical cutting speeds of experimental conditions. vc = 200 m/min or more, it is adequate The ratio of the feed force Ff to the for most approximate analyses to assume Table 3 lists specific cutting forces in re- cutting force Fc depends on the tool that FP is of the same rough magnitude lation to the undeformed chip thickness h. cutting edge angle κr. Assuming that as Ff.

16 | DKI Monograph i.18 No. Machining Tool Feed range Depth of cut Cutting Cutting tool geometry Notes Source operation material or unde- or undeformed speed Machina- α-γ-λ-ε-K; r formed chip chip width v c bility [degrees; mm] thickness a or b [m/min] p group f or h [mm] [mm]

1 Cylindrical HM-K 10 f = 0,05-0,315 ap = 2,5 180 I 6-0-0-ε-90/75/45; 0,5 Dry [7] turning II 8-5-0-ε-90/75/45; 0,5 cutting III 10-20-0-ε-90/75/45; 0,5

2 Cylindrical HSS (M2-AlSI) h = 0,05-0,28 a3p =Der 2,54 Begriff 15-90Zerspanbarkeit – α-20-λ-ε-90; r Dry [11] 21 turning cutting

3 Turning SS u. HM f = 0,1-0,8 aDap :f= die2:1 bis Vorschubgeschwindigkeit 10:1 - I u. II SS 8-0-0/8-90-45; in der Regel 0,5/2 im VergleichDry [12] mit der Schnittgeschwindigkeit HM 5-6-0/8-90-45; 0,5/2 cutting sehr klein und die VorschubkraftIII SS 8-14/18-0/8-90-45;ebenfalls weitaus 0,5/2 kleiner als die Schnittkraft ist, darf für die HM überschlägige Berechnung der Netto-Zerspanungsleistung die Vorschubleistung vernachläs- 4 Cylindrical HM h = 0,04-0,6 ap = 2,5 200 – 5-15-λ-ε-90; r Dry [13] turning sigt werden. Damit errechnet sich die Netto-Antriebsleistungcutting wie folgt:

5 Fly cutting HSS f = 0,08-0,6 a = 8-9 40 – 5-10-0-90-90; r - [14] p F v b = 4-12 P ' = c c e 60000 (15) 6 Cylindrical HM-K 10 f = 0,08-0,32 ap = 2,5 3 Der200 Begriff Zerspanbarkeit– 5-6-0-90-70; 0,4 Dry [15] 21 turning cutting Mit: Pe’ Netto-Antriebsleistung in kW 7 Cylindrical HSS u. HM f = 0,1-0,6 ap = 1 u. 2 Da 32die VorschubgeschwindigkeitHSS 8-0-0/8-90-45; in der 0,5/2 Regel imDry Vergleich[16] mit der Schnittgeschwindigkeit turning Fc HM Schnittkraft5-6-0/8-90-45; in N 0,5/2 cutting sehr klein undvc die Vorschubkraft Schnittgeschwindigkeit ebenfalls weitaus in m/minkleiner als die Schnittkraft ist, darf für die 8 Cylindrical HM f = 0,05-0,14 a = 1 200 HM 8-10-0-84-96; 0,4 Oil DKI p überschlägige60000 Berechnung Umrechnungsfaktor der Netto-Zerspanungsleistung in (N m)/(kW die min)Vorschubleistung vernachläs- turning3 Der Begriff Zerspanbarkeit 21 sigt werden. Damit errechnet sich die Netto-Antriebsleistung wie folgt: Table 2: Information on the experimental conditions relevantMehrschneidige to the specific cuttingWerkzeuge forces listed arbeiten in Table 1 i. A. mit kleinern Spanungsdicken h als einschneidige. Bei ihnen kann die Netto-Antriebsleistung aus dem je Zeiteinheit zu zerspanenden Werk- Da die Vorschubgeschwindigkeit in der Regel im Vergleich mit der SchnittgeschwindigkeitF v F F 0,3 F (11) for most approximate calculations of removedP ' = perc unitc time3 and per unit of P ≈ sehrf ≈ kleinc und die Vorschubkraft stoffvolumen,ebenfalls weitaus dem kleinerZeitspanungsvolumen als die Schnittkrafte 60000Vw ist,in darfcm /minfür die und (15) einem auf Zeit und Leistung overall cutting power. The net machine power supplied). bezogenen Zeit-Leistungs-Spanungsvolumen V in cm3 / (min kW), errechnet werden. While theüberschlägige magnitude of Berechnungthese forces is derpower Netto-Zerspanungsleistung can therefore be computed dieas Vorschubleistungwp vernachläs- of interestsigt when werden. dimensioning Damit errechnet work- sichfollows: die Netto-AntriebsleistungMit: wiePe’ folgt:For Netto-Antriebsleistung multipoint tools, the following in kW Fc Schnittkraft in N piece clamps, tool holders, etc., an Für die oben angegebenen mehrschneidigenrelationship applies: Werkzeuge gilt folgende Beziehung: approximate calculation of the cutting vc Schnittgeschwindigkeit in m/min F v power is important in order to deter- P ' c c 60000 Umrechnungsfaktor in (N m)/(kW min) e = (15) (15) mine the power requirements of the 60000 Vw Mehrschneidige Werkzeuge P arbeiten' = i. A.(16) mit kleinern Spanungsdicken (16) h als einschneidige. machine tool performing the cutting e Bei ihnen kann die Netto-AntriebsleistungVwp aus dem je Zeiteinheit zu zerspanenden Werk- operation,Mit: whereby the machinePe’ effi- Netto-Antriebsleistungwhere: in kW stoffvolumen, dem Zeitspanungsvolumen V in cm3/min und einem auf Zeit und Leistung ciency must also be taken into account.Fc Schnittkraft Pe’ Net inmachine N power in kW Pe’ Net machinew power in kW Pe’ Netto-Antriebsleistung in kW 3 vc Schnittgeschwindigkeitbezogenen in Zeit-Leistungs-Spanungsvolumen m/min 3 Vwp in cm / (min kW), errechnet werden. According to the DIN 6584 standard, FV w Cutting Zerspantes force in NWerkstoffvolumen V in cmS tock/min removal rate (volume of 60000 Umrechnungsfaktorc in (N m)/(kW min)w 3 the effective cutting power is the Vwp Spezifisches Zerspanvolumen in cmworkpiece/min kWmaterial removed Für die oben angegebenen mehrschneidigen Werkzeuge3 gilt folgende Beziehung: productMehrschneidige of the effective cutting Werkzeuge force arbeiten vc i. Cutting A. mit speed kleinern in m/min Spanungsdicken hper als unit einschneidige. time in cm /min) F and the resultant cutting velocity Das spezifische Zerspanvolumen Vwp ist direkt proportional zu der spezifischen Schnittkraft, e Bei ihnen kann die Netto-Antriebsleistung aus dem je Zeiteinheit zu zerspanenden Werk- ve and is also the sum of the cutting 6wie0000 folgende Conversion Ableitung factor in zeigt: Vwp Spe cificV stock removal rate 3 P ' = w (16) power stoffvolumen,Pc and the feed powerdem PZeitspanungsvolumenf. (N • m)/(kW Vw in • min)cm /min und einem auf (volumee Zeit und of workpieceLeistung material Vwp 3 removed per unit time and bezogenen Zeit-Leistungs-Spanungsvolumen Vwp in cm / (min kW), errechnet werden. P = F • v = P + P (12) Cutting tools with multiple active cut- Vw A pervc unit ofA powervc supplied1 in e e e c f Vwp = = = = (17) Pe’ Netto-Antriebsleistung in kW 3 ting edges generally work with smaller Pc Fc cmvc /(minkc3 • AkW) v )c kc Vw Zerspantes Werkstoffvolumen in cm /min Pc = FFürc • v diec (13) oben angegebenen mehrschneidigenundeformed chip thicknessesWerkzeuge h thangilt folgende Beziehung:3 Vwp Spezifisches Zerspanvolumen in cm /min kW single-point tools. The net machine The specific stock removal rate Vwp is 3 P = F • v (14) powerAuf required die Einheit when cmworking/min with kW umgerechnetdirectly proportional ergibt sich to folgendes:the specific f f f V Das spezifische Zerspanvolumen Vwp ist direkt proportional zu der spezifischen Schnittkraft, multipointP ©= toolsw can be calculated from (16)cutting force, as the following deriva- As the tool feed velocity (‘feed rate’) the stocke removalwie rate folgende V in cm Ableitung3/min zeigt:tion shows: Vwp w 60000 is generally much lower than the (i.e. the volume of workpiece material Vw Vwp = = 18) cutting velocity and the feed force is removed per unit time) and a specific VwPc A vckc A vc 1 Pe’ Netto-Antriebsleistung in kW 3 Vwp = = = = (17)(17) also much smaller than the cutting stock removal rate Vwp in cm / (min • kW) 3 Pc Fc vc kc A vc kc force, theVw feed power Zerspantes can be neglectedWerkstoffvolumen (i.e. the volumein cm /minof workpiece material 3 Vwp spezifische3 Spanungsleistung in cm /min kW Vwp Spezifisches Zerspanvolumen in cm /min kW 3 Vw zerspantes Werkstoffvolumen3 in cm /min Auf die Einheit cm /min kW umgerechnet ergibt DKI Monograph sich folgendes: i.18 | 17 Das spezifische ZerspanvolumenP cV wp ist Schnittleistung direkt proportional in kW zu der spezifischen Schnittkraft, 2 wie folgende Ableitung zeigt: kc spezifische Schnittkraft in N/mm 3 2 V 60000 60000 Konstante in cm N/mm min kW w Vwp = = 18) Pc kc VFür dieA inv Tab. 1A aufgeführeten v 1 Werkstoffe nennt Tab. 4 Vwp-Werte für die bei mehrschneidi- V = w = c = c = wp (17) 3 genPc ZerspanungswerkzeugenFc vcVwp kc spezifischeA vc k cSpanungsleistung üblichen Spanungsdicken in cm /min kW h = 0,08 bis 0,315 mm. 3 Vw zerspantes Werkstoffvolumen in cm /min Pc Schnittleistung in kW 3 2 Auf die Einheit cm /min kW umgerechnet ergibtkc sich spezifische folgendes: Schnittkraft in N/mm 3 2 Die Kennwerte60000 der Konstante mechanischen in cm Eigenschaften N/mm min derkW Knetwerkstoffen in den folgenden Tabellen sind 60000 Vw Für die in Tab. 1 aufgeführeten Werkstoffe nennt Tab. 4 Vwp-Werte für die bei mehrschneidi- Vwp = = 18) Pc gen Zerspanungswerkzeugenkc üblichen Spanungsdicken h = 0,08 bis 0,315 mm.

3 Vwp spezifische Spanungsleistung in cm /min kW 3 Vw zerspantes Werkstoffvolumen in cm /min Die Kennwerte der mechanischen Eigenschaften der Knetwerkstoffen in den folgenden Tabellen sind Pc Schnittleistung in kW 2 kc spezifische Schnittkraft in N/mm 60000 Konstante in cm3 N/mm2 min kW

Für die in Tab. 1 aufgeführeten Werkstoffe nennt Tab. 4 Vwp-Werte für die bei mehrschneidigen Zerspanungswerkzeugen üblichen Spanungsdicken h = 0,08 bis 0,315 mm.

Die Kennwerte der mechanischen Eigenschaften der Knetwerkstoffen in den folgenden Tabellen sind 3 Der Begriff Zerspanbarkeit Material Undeformed chip thickness h [mm] 21 Notes on experi- Da die Vorschubgeschwindigkeit inDesignation der Regel imNum Vergleich- Num- 0,08mit der0,1 Schnittgeschwindigkeit0,125 0,16 0,20 0,25 0,315 0,4 0,5 0,63 0,8 1,0 1,25 1,6 mental ber ber condi- sehr klein und die Vorschubkraft ebenfalls weitaus(EN) kleiner(UNS) als die Schnittkraft ist, darf für die tions überschlägige Berechnung der Netto-Zerspanungsleistung die Vorschubleistung vernachläs- Table 2 sigt werden. Damit errechnet sich dieMachinability Netto-Antriebsleistung group I / Type I alloys wie folgt: CuSP CW114C C14700 979 963 948 932 918 904 889 874 861 847 833 820 807 793 1) CuTePF v CW118C C14500 1232 1200 1168 1134 1104 1075 1045 1016 989 962 935 910 886 860 1) P ' =CuZn35Pb2c c CW601N C34200 1349 1293 1240 1183 1134 1087 1040 994 953 912 871 835 800 764 4) e 60000 (15) CuZn39Pb3 CW614N C38500 1010 940 875 809 753 701 651 603 562 522 483 450 419 387 1) CuZn40Pb2 CW617N C37700 1122 1045 973 899 837 779 724 670 624 580 537 500 466 430 1) Mit: Pe’ Netto-Antriebsleistung in kW Fc SchnittkraftCuSn5Zn5Pb5-C*) in N CC491K C83600 1114 1065 1019 969 927 887 847 807 772 737 703 672 643 612 7) vc SchnittgeschwindigkeitCuSn7Zn4Pb7-C CC493K in m/minC93200 2567 2433 2307 2173 2060 1953 1847 1744 1653 1564 1477 1400 1327 1251 7) 60000 UmrechnungsfaktorCuSn5Zn5Pb2-C CC499Kin (N C92220m)/(kW––––––––––––––– min) Machinability group II / Type II alloys Mehrschneidige Werkzeuge arbeiten i. A. mit kleinern Spanungsdicken h als einschneidige. CuNi18Zn19Pb1 CW408J C76300 1303 1286 1269 1250 1234 1217 1200 1183 1168 1151 1135 1120 1105 1089 1) Bei ihnen kann die Netto-AntriebsleistungCuZn35Ni3Mn2AlPb aus dem CW710R je– Zeiteinheit1623 1559 zu 1498zerspanenden1433 1376 1322Werk- 1268 1215 1167 1119 1072 1030 989 946 1) 3 stoffvolumen, dem ZeitspanungsvolumenCuZn37Mn3Al2PbSi Vw in CW713Rcm /min– und1542 einem1432 auf1330 Zeit1227 und1140 Leistung1059 981 907 842 780 721 670 622 574 3) 3 bezogenen Zeit-Leistungs-SpanungsvolumenCuZn38Mn1Al Vwp CW716R in cm–/ (min1102 kW),1012 errechnet930 847 werden.778 715 655 598 549 503 459 422 388 353 5) CuAl10Fe5Ni5-C CC333G – 2215 2077 1946 1812 1698 1592 1489 1389 1302 1218 1136 1065 998 929 6) Für die oben angegebenen mehrschneidigenCuSn12Ni2-C Werkzeuge CC484K C95500 gilt folgende1955 1833 Beziehung:1718 1599 1499 1405 1314 1226 1149 1075 1003 940 881 820 6) CuZn33Pb2-C CC750S C91700 1540 1387 1249 1112 1001 902 809 723 651 584 522 470 423 377 3) Machinability group III / Type III alloys Vw PCuAg0,10' = CW013A C11600 2946 (16) 2700 2475 2248 2061 1889 1726 1573 1441 1317 1200 1100 1008 916 2) e V CuNi2Si wp CW111C C64700 1810 1735 1663 1586 1521 1458 1395 1333 1278 1223 1169 1120 1074 1024 1) CuAl8Fe3 CW303G C61400 1528 1468 1410 1349 1296 1245 1194 1144 1099 1054 1010 970 932 891 1) Pe’ Netto-Antriebsleistung in kW CuAl10Ni5Fe43 CW307G C63000 1760 1714 1668 1620 1577 1535 1493 1451 1413 1374 1335 1300 1266 1229 1) Vw Zerspantes Werkstoffvolumen in cm /min CuSn8 3 CW453K C52100 1519 1486 1453 1417 1386 1355 1325 1293 1265 1236 1207 1180 1154 1126 1) Vwp Spezifisches Zerspanvolumen in cm /min kW CuZn37 CW508L C27400 1907 1828 1752 1671 1602 1536 1470 1404 1346 1288 1231 1180 1131 1079 1) Das spezifische Zerspanvolumen VCuZn20Al2Aswp ist direkt proportional CW702R C68700 zu1540 der1387 spezifischen1249 1112 Schnittkraft,1001 902 809 723 651 584 522 470 423 377 3) wie folgende Ableitung zeigt:

*) The low value can be explained by the low cutting velocities (vc = 32 m/min) used in the tests. V Table 3:A Specificv cuttingA forcev kc in N/mm²1 as a function of the undeformed chip thickness h in mm for the materials listed in Table 1. (Note: data drawn from wa variety of sources.)c Please notec that because of the differences in the experimental conditions used, data from different sources cannot be directly compared. Vwp = = = = (17) Pc Fc vc kc A vc kc

Converting to units of cm3/(min • kW) 60000 Conversion factor in piece surface of a predefined quality, i.e. Auf die Einheit cm3/min kW umgerechnetyields: ergibt sich folgendes: cm3 • N/(mm2 • min • kW) the roughness of the surface must not (= N • m/(kW • min)) exceed a certain level. Decorative sur- 60000 faces are often required when turning Vw Table 4 provides values of V for the components from free-cutting brass V = = (18) 18) wp wp materials listed in Table 1 at unde- (e.g. CuZn39Pb3) and this frequently Pc kc formed chip thicknesses h in the range requires the part to be smoothed or Vwp Spe 3 cific stock removal rate in 0.08 to 0.315 mm that is typical when precision finished. The achievable Vwp spezifische Spanungsleistung in cmcm/min3/(min •kW kW) machining with multipoint tools. surface quality is therefore regarded as 3 Vw zerspantes Werkstoffvolumen in cm /min the most important machinability 3 Pc Schnittleistung in kW Vw S tock removal rate in cm /min criterion when assessing the machin- 2 kc spezifische Schnittkraft in N/mm 3.3 Surface quality ability of free-cutting alloys such as 3 2 60000 Konstante in cm N/mm minPc kWCutting power in kW As with other materials, finish-machin- CuZn39Pb3, CuZn39Pb2, CuZn40Pb2, ing of copper or copper alloys should CuZn30Pb3, CuNi18Zn19Pb1, CuTeP, 2 Für die in Tab. 1 aufgeführeten Werkstoffe kc Spe nenntcific cutting Tab. force4 V wpin-Werte N/mm fürgenerally die bei produce mehrschneidi- a machined work- CuPb1P and CuSP. gen Zerspanungswerkzeugen üblichen Spanungsdicken h = 0,08 bis 0,315 mm. 18 | DKI Monograph i.18

Die Kennwerte der mechanischen Eigenschaften der Knetwerkstoffen in den folgenden Tabellen sind Material Undeformed chip thickness h in [mm] Notes on experimental Designation Number (EN) Number (UNS) 0,08 0,1 0,125 0,16 0,20 0,25 0,315 conditions 3 Der Begriff Zerspanbarkeit Table 2 27 3 Der Begriff Zerspanbarkeit 27 Machinability group I / Type I alloys sen – d.h. eine bestimmte Rauheit darf nicht überschritten werden. Insbesondere bei Dreh- CuSP CW114C C14700 sen –61,3 d.h. eine62,3 bestimmte63,3 Rauheit64,4 65,4 darf nicht 66,4 überschritten 67,5 1) werden. Insbesondere bei Dreh- teilen aus Automatenmessing (z. B. aus CuZn39Pb3) werden oft dekorative Oberflächen CuTeP CW118C C14500 teilen 48,7aus Automatenmessing50,0 51,4 52,9 (z. 54,4B. aus 55,8 CuZn39Pb3) 57,4 1) werden oft dekorative Oberflächen CuZn35Pb2 CW601N C34200 gefordert,44,5 die 46,4 ein Schlichten 48,4 50,7 oder 52,9Feinschlichten55,2 57,7 des 4)Drehteils bedingen. Daher ist für die gefordert, die ein Schlichten oder Feinschlichten des Drehteils bedingen. Daher ist für die CuZn39Pb3 CW614N C38500 Beurteilung59,4 63,8der Zerspanbarkeit68,6 74,2 79,7von Automatenwerkstoffen,85,6 92,2 1) wie z. B. CuZn39Pb3, Beurteilung der Zerspanbarkeit von Automatenwerkstoffen, wie z. B. CuZn39Pb3, CuZn40Pb2 CW617N C37700 CuZn39Pb2,53,5 57,4 CuZn40Pb2,61,7 CuZn30Pb3, 66,7 71,7 CuNi18Zn19Pb1,7 7,0 82,9 1) CuTeP, CuPb1P und CuSp, die CuZn39Pb2, CuZn40Pb2, CuZn30Pb3, CuNi18Zn19Pb1, CuTeP, CuPb1P und CuSp, die CuSn5Zn5Pb5-C *) CC491K C83600 Beurteilung20,5 der 21,7 erreichbaren23,0 24,5 Oberflächenqualität 26,0 27,5 29,2 als das7) wichtigste Zerspanbarkeitskriterium CuSn7Zn4Pb7-C CC493K C93200 Beurteilung23,4 der24,7 erreichbaren26,0 27,6 Oberflächenqualität29,1 30,7 32,5 als das7) wichtigste Zerspanbarkeitskriterium anzusehen. CuSn5Zn5Pb2-C CC499K – anzusehen.––– ––––– Machinability group II / Type II alloys Zur quantitativen Beurteilung der Oberflächengüte spanend bearbeiteter Flächen wird die CuNi18Zn19Pb1 CW408J C76300 Zur quantitativen46,1 46,7 Beurteilung47, 3 48,0 der 48,6Oberflächengüte 49,3 48,2 spanend 1) bearbeiteter Flächen wird die CuZn35Ni3Mn2AlPb3 Der Begriff ZerspanbarkeitCW710R – Rauheit,37,0 meist 38,5 gemessen40,1 in 41,9m, herangezogen.43,6 45,4 47,Dabei 3 1)interessiert 27 vor allem die Querrauheit Rauheit, meist gemessen in m, herangezogen. Dabei interessiert vor allem die Querrauheit CuZn37Mn3Al2PbSi CW713R – (kinematische65,9 71,9 Rauheit),78,4 gemessen 86,3 94,2 in Vorschubrichtung, 102,7 112,4 3) weil sie meist größer ist als die in (kinematische Rauheit), gemessen in Vorschubrichtung, weil sie meist größer ist als die in CuZn38Mn1Alsen – d.h. eine bestimmteCW716R Rauheit – Richtung darf 54,5nicht der überschritten59,3 Schnittgeschwindigkeit65,4 werden. 70,8 Insbesondere7 7,1 gemessene83,9 91,6bei Längsrauheit Dreh- 5) (Schnittflächenrauheit). Die CuAl10Fe5Ni5-C CC333G – Richtung27,1 der28,9 Schnittgeschwindigkeit30,8 33,1 35,3 gemessene37,7 40,3 Längsrauheit6) (Schnittflächenrauheit). Die teilen aus Automatenmessing (z. kinmetischeB. aus CuZn39Pb3) Rauheit ergibtwerden sich oft aus dekorative dem Eckenradius Oberflächen und der Relativbewegung zwischen CuSn12Ni2-C CC484K C95500 kinmetische30,7 32,7Rauheit34,9 ergibt 37,5sich aus 40,0 dem42,7 Eckenradius45,7 6) und der Relativbewegung zwischen gefordert, die ein Schlichten oder WerkzeugFeinschlichten und Werkstück.des Drehteils bedingen. Daher ist für die CuZn33Pb2-C CC750S C91700 39,0 43,3 48,0 54,0 59,9 66,5 74,2 3) Beurteilung der Zerspanbarkeit Werkzeugvon Automatenwerkstoffen, und Werkstück. wie z. B. CuZn39Pb3, Machinability group III / Type III alloys CuAg0,10CuZn39Pb2, CuZn40Pb2,CW013A CuZn30Pb3,C11600 Die theoretisch 20,3CuNi18Zn19Pb1, 22,2 erzielbare24,2 CuTeP, Rautiefe26,7 CuPb1P29,1 Rt,th bei31,8 und einschneidigem CuSp,34,8 die2) Werkzeug (z. B. beim Drehen) Die theoretisch erzielbare Rautiefe Rt,th bei einschneidigem Werkzeug (z. B. beim Drehen) CuNi2SiBeurteilung der erreichbarenCW111C C64700 Oberflächenqualitätlässt 33,2sich aus34,6 alsdem das36,1 Vorschub wichtigste37,8 f undZerspanbarkeitskriterium 39,5 dem41,2 Eckenradius43,0 1) r (Abb. 14) nach folgender Formel lässt sich aus dem Vorschub f und dem Eckenradius r (Abb. 14) nach folgender Formel CuAl8Fe3anzusehen. CW303G C61400 errechnen:39,3 40,9 42,6 44,5 46,3 48,2 50,3 1) CuAl10Ni5Fe4 CW307G C63000 errechnen:34,1 34,5 36,0 37,0 38,1 39,1 40,2 1) CuSn8Zur quantitativenCW453K Beurteilung C52100 der Oberflächengüte39,5 40,4 spanend41,3 bearbeiteter42,3 43,3 Flächen44,3 45,32 wird 1)die 2 f CuZn37 CW508L C27400 31,5 32,8 34,3 35,9R = 37,5r 39,1r 40,82 1) (19) Rauheit, meist gemessen in m, herangezogen. Dabei interessiert t,vorth allem die 2 Querrauheitf4 CuZn20Al2As CW702R C68700 39,0 43,3 48,0 54,0Rt,th =59,9r 66,5r 74,2 3) (19) (kinematische Rauheit), gemessen in Vorschubrichtung, weil sie meist größer ist4 als die in *) The low value can be explained by the low cutting velocities (vc = 32 m/min) used in the tests. Richtung der Schnittgeschwindigkeit gemessene Längsrauheit (Schnittflächenrauheit). Die Table 4: Specific stock removal rate Vwp in cm³/(min·kW) asÜber a function eine of theReihenentwicklung undeformed chip thickness nachh in mm Taylor for the materials lässt listedsich in derTable 1.Ausdruck vereinfachen, sodass (Note: data drawn from a variety of sources.) Über eine Reihenentwicklung nach Taylor lässt sich der Ausdruck vereinfachen, sodass kinmetische Rauheit ergibt sich ausüberschlägig dem Eckenradius gilt: und der Relativbewegung zwischen Werkzeug und Werkstück. überschlägig gilt: Surface roughness, which is usual- The theoretically achievable peak-to- f 2 ly measured in µm, is the property valley roughness Rt,th with a single 2 Rt,th f (20) (20) typicallyDie used theoretisch to quantitatively erzielbare assess Rautiefepoint operation Rt,th bei such einschneidigem as turning can Werkzeug 8(z. B. beim Drehen) R , r (20) the quality of a machined surface. be calculated from the feed f and the t th lässt sich aus dem Vorschub f und dem Eckenradius r (Abb. 14) nach8 r folgender Formel The transverse roughness (kinematic nose radius rε (Fig. 14) by means of the For most machining operations the roughness),errechnen: which is measured in the followingWeil equation: für die spanende Bearbeitungrequired die peak-to-valley Rautiefe meistsurface vorgegebenrough- ist, ist zu ermitteln, mit direction of feed motion, is usually Weil für die spanende Bearbeitungness is usually die Rautiefe specified, meistso that vorgegebenEq. 20 ist, ist zu ermitteln, mit welchem Vorschub f bei gegebenem Eckenradius gedreht werden muss. Deshalb wird obige larger than the longitudinal roughness 2 can be used to determine the required (cut surface roughness) measured in welchem2 Vorschubf f bei gegebenemfeed for aEckenradius given nose radius. gedreht The above werden muss. Deshalb wird obige R =Beziehungr r nach dem (19) Vorschub (19) aufgelöst: the direction of primary motion and t,th Beziehung nach4 dem Vorschubexpression aufgelöst: can be rearranged to yield is therefore of greater interest. The the feed: kinematic roughness is determined by This expression can be simplified by a f 8 r Rt,th (21) the tool’sÜber nose eine radius Reihenentwicklung and the relative Taylor nach series Taylor expansion, lässt whichsich yieldsder Ausdruckf vereinfachen,8 r Rt,th (21) sodass (21) motion of the tool and the workpiece. the following approximation: überschlägig gilt: Für vorgegebene Rautiefen könnenThe theoretically die theoretisch required feederforderlichen f to Vorschübe bei gegebenem Für vorgegebene Rautiefen könnenproduce die a specified theoretisch peak-to-valley erforderlichen Vorschübe bei gegebenem Eckenradius2 r Tab. 5 entnommen werden. An der Drehmaschine ist, wenn der theoretische Eckenradiusf r Tab. 5 entnommen werden. An der Drehmaschine ist, wenn der theoretische Rt,th Wert nicht eingestellt werden (20) kann, der nächst DKI kleinere Monograph Vorschubwert i.18 | 19 zu wählen. Wert8 r nicht eingestellt werden kann, der nächst kleinere Vorschubwert zu wählen. In der Praxis ergeben sich jedoch oftmals erhebliche Abweichungen von der theoretischen In der Praxis ergeben sich jedoch oftmals erhebliche Abweichungen von der theoretischen Weil für die spanende BearbeitungRautiefe, die Rautiefe die im meist Wesentlichen vorgegeben auf dreiist, istUrsachen zu ermitteln, zurückgeführt mit werden können: welchem Vorschub f bei gegebenemRautiefe, Eckenradius die im gedreht Wesentlichen werden auf muss. drei UrsachenDeshalb wird zurückgeführt obige werden können: Beziehung nach dem Vorschub aufgelöst:a) Bei der Feinbearbeitung – insbesondere mit niedrigen Vorschüben (f < 0,1 mm/U) – a) Bei der Feinbearbeitung – insbesondere mit niedrigen Vorschüben (f < 0,1 mm/U) – können sich im Bereich der Nebenschneide und des Schneidenradius Verschleißrie- können sich im Bereich der Nebenschneide und des Schneidenradius Verschleißrie- f 8 r Rfen ausbilden, die (21) eine Abweichung vom theoretischen Drehprofil bewirken. fent,th ausbilden, die eine Abweichung vom theoretischen Drehprofil bewirken.

Für vorgegebene Rautiefen können die theoretisch erforderlichen Vorschübe bei gegebenem

Eckenradius r Tab. 5 entnommen werden. An der Drehmaschine ist, wenn der theoretische Wert nicht eingestellt werden kann, der nächst kleinere Vorschubwert zu wählen.

In der Praxis ergeben sich jedoch oftmals erhebliche Abweichungen von der theoretischen Rautiefe, die im Wesentlichen auf drei Ursachen zurückgeführt werden können:

a) Bei der Feinbearbeitung – insbesondere mit niedrigen Vorschüben (f < 0,1 mm/U) – können sich im Bereich der Nebenschneide und des Schneidenradius Verschleißrie- fen ausbilden, die eine Abweichung vom theoretischen Drehprofil bewirken. Abb. 14: Geometrische Eingriffsverhältnisse beim Drehen

roughness Rt,th using a cutting tool with a given nose radius r can be ε z found by consulting Tab. 5. If the theoretically required feed cannot be set on the lathe, the next lower feed setting should be chosen. Rt,th However, in practical applications the rε x rε –R peak-to-valley roughness achieved t,th f often deviates significantly from the 2 M1 M2 2 f κ R = rε rε −− theoretical value. This can be traced to r f/2 th,t 4 the following three main causes: oroder f f 2 R = th,t r8 ● Finish machining, particularly ε when carried out with small feeds (f < 0.1 mm/rev), can lead to the RangeGültigkeitsbereich: of validity: f < 2 re cos(κr + εr – 90) und κr + εr < 180° formation of wear grooves in the vicinity of the minor cutting edge and Fig. 14: Geometric relationships when turning the nose radius, resulting in a deviation from the theoretical profile of the machined surface. The transverse roughness of the work- value [17, 18]. When machining with a piece surface that can be achieved also cutting tool of defined geometry (i.e. ● At higher feeds (f > 0.1 mm/rev), depends on the tool angles, particu- excluding operations such as grin- the continuous© WZL/Fraunhofer growth of flank IPT wear, larly the rake angle. Increasing the rake ding, lapping, honing, etc.), it can be Seite 15 particularly at the nose radius, leads angle improves work surface quality. roughly assumed that the grain size to a deterioration in the quality of the The theoretically achievable value can of the work material approximately machined surface. be more closely approximated when represents the lowest degree of surface machining copper and copper alloys roughness achievable in practice. ● As discussed earlier in Section 2.3, than when machining other metals. When high demands are placed upon there is a range of cutting speeds in However, increasing the rake angle the quality of the work surface finish, which built-up edge (BUE) formation reduces the wedge angle and thus re- the use of diamond-tipped tools at is likely to occur. Periodic breakage of duces the tool life. As is the case with high cutting speeds and low feeds is the BUE and displacement of these other metals, machining copper and recommended. Such a configuration pieces of BUE often causes a signif- copper alloys at high cutting speeds can produce mirror surface finishes. icant deterioration in the quality of produces a better work surface quality the machined surface. Built-up edges than when machining at lower speeds. When machining with multipoint tools form when heavily strained workpiece (e.g. milling operations), a form error material temporarily deposits on the The expressions (19), (20) and (21) are known as ‘waviness’ may be superim- cutting edge, giving the cutting edge useful approximations when dealing posed on the peak-to-valley height Rt an irregular shape. When the BUE with fine-grained materials; for more of the surface. The ‘wavelength’ corre- breaks periodically, the bits of BUE can coarsely grained material, the actual sponds to the feed per revolution, the then become welded to the chip or the peak-to-valley roughness Rt is signif- amplitude reflects the tool runout error machined workpiece surface. icantly larger than the calculated if this is greater than about 10 µm. The

Nose radius Feed f in mm/rev = f (Rth,rε) rε [mm] Fine finishing Finishing Rough cutting

  

Rt,th 4 µm Rt,th 6,3 µm Rt,th 16 µm Rt,th 25 µm Rt,th 63 µm Rt,th 100 µm

0,5 0,13 0,16 0,26 0,32 0,50 063

1,0 0,18 0,22 0,36 0,45 0,71 0,89

1,5 0,22 0,27 0,44 0,55 0,87 1,10

2,0 0,25 0,31 0,50 0,63 1,00 1,26

3,0 0,31 0,38 0,62 0,77 1,22 1,55

Tab. 5: Feed f in mm/rev as a function of the required theoretical roughness Rt,th and the nose radius rε

20 | DKI Monograph i.18 quality of the surface can be improved chip flow and chip removal. Pure cop- The first five chip shapes depicted in in face milling operations by using a per and solid-solution copper alloys Figure 16: ribbon, tangled, corkscrew, milling cutter with indexable teeth with a high copper content belong conical helical and long cylindrical inserts that have an ‘active minor cut- to the group of materials that have a chips are not ideal as they make it ting edge’, that is, the inserts have a tendency to produce long continuous difficult to eject the chip from the chamfer on the minor cutting edge so chips if the chip is allowed to form cutting zone. Corkscrew chips prefer that the chamfered edge lies parallel and flow in an uninterrupted manner. to migrate over the flank of the tool to the workpiece surface with a cutting These materials are generally less easy causing damage to the tool holder edge angle of κr = 0°. The chamfer to machine. and to those sections of the cutting on the minor cutting edge may be up edge outside the contact zone. Ribbon to several millimetres long. The feed The assessment of whether a chip chips, tangled chips and discontinuous per tooth should not exceed 2/3 of the shape is unfavourable, acceptable or chips all present an injury hazard for active chamfer length. If the minor good (see Fig. 16) is made on the basis persons near the machine. Fine needle cutting edge is larger than the feed per of the following criteria: chips can be formed when machining revolution, overlapping reduces the free-cutting brasses. Needle chips are unavoidable runout error and improves ● Transportability: The chips should undesirable as they tend to clog the the machined surface finish. be of a shape that enables them to chip conveyor systems and cutting fluid be removed easily from the machine’s filters and increase the risk of injury to cutting zone and they should not be so the machine operator. 3.4 Chip shape small that they clog up the chip con- In addition to the type of chip form- veyor system or the cutting fluid filters. Machining homogeneous copper ed, the shape of the chip is an materials, such as pure coppers and important criterion for assessing the ● Injury hazard: Injury to operating high copper copper-zinc alloys, tends machinability of a material. A distinc- personnel from sharp-edged tangled to produce long flowing ribbon chips tion is often made between materials or corkscrew chips should be avoided. if the area of the uncut chip is large that produce short chips and those and the chip is allowed to develop that tend to form long chips. Short ● Risk of damage: The chips should unhindered. Tangled or snarled chips chips, with the exception perhaps of not damage the workpiece, cutting tool tend to form at low or medium feed discontinuous and needle chips, tend or machine tool. rates, while corkscrew chips arise when to be more favourable with regard to machining with small nose radii, small

Rz1 Rz1 Rz2 (R(=R Rzmax2 (R(= R) max) Rz5 Rz5 Rz4 Rz4 Rz3 Rz3

lr lr ln ln 5 5 Sampling length 1 1 lr:lr: Einzelmessstrecke Einzelmessstrecke Rz Rz= = Rz Rz ln:ln:Evaluation Messstrecke Messstrecke length )5( ∑)5( ∑i i 5 i=1 5 i=1 Individual roughness depth (peak-to-valley) Rzi:Rz Einzelrautiefeni: Einzelrautiefen Rz:Rz:Mean Rautiefe roughness Rautiefe (arithmetischer (arithmetischerdepth (‘ten-point Mittelwert Mittelwert height’): der Einzelrautiefen arithmeticder Einzelrautiefen mean Rz ofi aufeinande the Rz individuali aufeinander- r- roughnessfolgenderfolgender depthsEinzelmessstrecken) Einzelmessstrecken)Rzi measured for five consecutive sampling lengths Rmax:R max:Maximummaxi mamax lRle roughness Rimaau lRl tif(ößtEiltiee Rfeau (depth:gr tif(ößtEiltieößtfe e (largestgr Eiößtnzee peak-to-valley lrauEinze tifitieflraue inner tifitiefe hlbdGhroughness iannerlb der hlbdGha lbG value esamder G within tmess-esam the tmess- evaluationstreck k)es)trec lengthk k)e)

Fig. 15: Roughness parameters (according to Mahr and DIN EN ISO 4287)

DKI Monograph i.18 | 21 depths of cut or large cutting edge cooling lubricant, cutting conditions It is often not possible to alter cutting angles. Corkscrew chips are particularly and tool geometry. The tool geometry conditions in order to modify the chip unfavourable because of the injury recommendations provided do not shape, as the cutting conditions have risk associated with their sharp edges. address the shape of chip breakers. usually been set by other criteria. In Conical helical chips can be expected such cases, chip shape formation can to form when machining with small Assuming that all other cutting condi- only be influenced by deploying chip depths of cut and when only the nose tions remain equal, short-breaking breakers. radius of the tool engages with the chips are generally more likely to workpiece. With increasing depth of form in workpiece materials of greater Generally speaking, chip formation is cut, the chips become longer and strength and with lower elongation. relatively unfavourable when machin- tubular in appearance. This chip form A coarse microstructure can also help to ing pure copper and solid-solution is not desirable as its bulkiness chip produce more favourable chip shapes high-copper copper alloys. The plas- makes it difficult to remove the chip when turning. This is the reason why tically deformed chip that is created from the cutting zone and convey it out cast alloys, particularly sanding-cast during the shearing process still has of the machine. alloys, exhibit better chip formation a high elongation after fracture and properties than wrought alloys. therefore tends not to break – a The preferred chip forms are short- fact that can cause problems for the breaking chips such as short tubular The cutting parameter with the greatest machining operation. The addition of chips, conical coiled chips and spiral influence on chip formation is the feed. chip-breaking alloying elements such chips. Arc chips, discontinuous chips The larger the feed, the shorter the as lead, tellurium or sulphur can sig- and needle chips are also regarded as chip. A negative angle of rake leads to nificantly improve the material’s chip acceptable when machining free-cut- a greater degree of chip compression, breaking properties (see Sec. 4.4). ting alloys such as free-cutting brasses, which generally promotes the forma- provided that the chips do not block tion of more favourable chip shapes. the filters of the chip conveyor system. In-creasing cutting speeds result in increasing cutting temperatures and the Factors influencing chip shape include: accompanying rise in the ductility of work material, tool material, machine the work material favours the forma- tool characteristics, chip breaking, tion of ribbon and continuous chips. Abb. 16: Spanformen beim Drehen und deren Beurteilungg[ nach [KLUF79]

unfavourableungggünstig brauchbaacceptabler goodgut brauchbaacceptabler

1 2 3 4 5 6 7 8 9 10

1 Ribbon1 Bands chipspäne 6 Short tubular chips6 kurze Wendelspäne 2 Tangled2 Wirrspäne (or snarled) chips 7 Conical coiled chips7 konische Wendelspäne 3 Corkscrew3 Flachwendelspäne (or washer-type helical) chips 8 Spiral chips 8 Spiralspäne 4 4Conical Schrägwendelspäne helical chips 9 Arc chips (or chip9 Spanlockencurls or short comma chips) 5 5Long lange tubular Wendelspäne chips 10 Discontinuous 10(or Bröckelspäneelemental or short comma) chips

Fig. 16: Classification of chip forms (Source: [19])

22 | DKI Monograph i.18 © WZL/Fraunhofer IPT Seite 17 4 Classification of copper-based materials into machinability groups

4.1 Standardization of copper composition-based classification or any single characteristic parameter, materials scheme is unsuitable for categorizing as is possible for properties such as The EN standards provide information materials according to their machin- mechanical strength or hardness. Any on the chemical composition, proper- ability because alloys in the same alloy assessment of machinability has to ties and main applications of copper group often exhibit different machin- take into account a number of differ- alloys, with a distinction being made ability properties. ent criteria. Which criteria are most between standards for wrought alloys important will depend on the particu- and standards for casting alloys. For lar machining operation being consid- each of these two main classes of alloy, 4.2 Machinability assessment ered – a fact that makes it impossible the materials are further classified into criteria to order machinability criteria into a alloy groups (see Table 6 and Table 7). As already discussed in Section 3, the single generally applicable system. Although the properties of copper machinability of a material is a highly materials are mainly determined by complex property that cannot be de- It is also not enough to simply consid- the composition of the alloy, this scribed adequately by any one term er one or two assessment criteria as

Designation Designation Further subdivisions (non-standardized) Copper - oxygen-containing; oxygen-free; non-deoxidized; silver-bearing oxygen-free; phosphorous deoxidized

Low-alloyed copper alloys - non age-hardenable (alloying elements < 5 %) age-hardenable Copper-aluminium alloys Aluminium bronze binär (without other elements)

Multi-component aluminium bronzes with additional Fe, Mn, Ni

Copper-nickel alloys - -

Copper-nickel-zinc alloys Nickel silver without additional alloying elements with added lead to improve machinability Copper-tin alloys Tin bronze binary alloy

Multi-component aluminium bronzes with additional zinc

Copper-zinc alloys, binary alloys Brass without other alloying elements

free-cutting brass with additional lead

Copper-zinc alloys, multi-component alloys Special brass with other alloying elements

Table 6: Wrought copper alloys (Classification as per CEN/TS 13388)

Designation Designation (non-standardized)

Copper unalloyed

Copper-chromium casting alloys Copper-chromium

Copper-zinc casting alloys Brass Special brass Copper-tin casting alloys Tin bronze

Copper-tin-zinc-lead casting alloys Gunmetal

Copper-aluminium casting alloys Aluminium bronze

Copper-manganese-aluminium casting alloys -

Copper-nickel casting alloys -

Table 7: Copper casting alloys (Classification as per EN 1982)

DKI Monograph i.18 | 23 complex relationships can exist be- machining performance of different However, as the test is very time-con- tween the various criteria. As discussed steels to be compared under typical suming and as significant quantities of in Section 3, the main criteria used to production conditions. material are required to perform the assess machinability are tool wear, tool The Copper Development Association test, data are not currently available life, chip formation, cutting forces and (CDA) subsequently applied the test to for all copper alloys. surface quality. a variety of copper-based materials in order to assess their relative machin- In Europe, the copper alloy used for Nevertheless, in order to provide prac- ability and to compare them with steel reference purposes is the free-cutting titioners with a basic overview of the and other alloys (see Fig. 1). The test brass CuZn39Pb3; in the USA it is the machinability of the materials avail- – generally known as ASTM E618 – is alloy CuZn36Pb3. These materials are able, a machinability rating index for based on the volume production of a considered to exhibit optimum ma- copper and copper alloys has become standard part, see Fig. 17. The standard chinability and are therefore assigned established in the literature and in the part itself is designed to be fabricated a defined machinability rating of 100. technical documentation published using the most common operations Decreasing machinability is repre- by copper producers. In Europe, the on automatic screw machines: rough sented by reducing the machinability reference material used for comparison turning, fine turning and drilling. The index in steps of 10 down to the mini- purposes is the lead-bearing free- goal of the test is to determine the mum value of 20. cutting brass CuZn39Pb3, while in the maximum number of standard parts USA it is the alloy CuZn36Pb3. These that can be produced in eight hours. Machinability indices for copper alloys reference materials have been assigned A number of test runs are performed are provided by the German Copper In- a machinability index of 100. The rating to optimize the machining parameters stitute (DKI) in its material data sheets, index ranges from 100 for copper alloys such that the form tool only needs to by the American Copper Development with excellent machinability charac- be changed after eight hours. The as- Association and by copper produ- teristics down to 20 for those that are sessment criteria used are dimensional cers. As a rule, machinability indices very hard to machine. accuracy and the surface finish of the are not based on specific measured machined part. The maximum number values. They provide a ranking system The machinability index assigned to a of parts produced is determined for based primarily on tool wear and chip Abb. 17: Musterbauteilparticular nach copper ASTMalloy is made E618 mainly undeach of diethe materials Position to be compared der Formwerkzeugeformation. A machinability index. Für may on the basis of experience and data and the values are then ranked. The therefore vary slightly in magnitude die Untersuchung andrawn den from Kupferlegierungen practical applications. resulting wurde machinability der index Halbzeugdurchmesser is there- depending on source. auf These values have received support from fore a measure of the productivity level 19 mm re duz ier t un d a di seriese of G experimentaleome t studies.r ie angepass In 1977, achievablet. Diduringes volume i st productionl aut ASTM E618 zulä ss ig wenn die Modifikationthe Americanfür alle standardization zu vergleichenden body operations using Werkstoffe one material compar- gleich4.3 The ist.effect of[THIE90, casting, cold ASTM developed a test that allows the ed to when another material is used. forming and age hardening on ASTM07] machinability When machining cast copper alloys, it is important to realize that the proper- FinishSchlicht form- ties of the casting skin are significantly Øø 25.4 25,4 mm mm werkzeugtool different to those of the core material. BHalbzeugar stock Generally speaking, the skin of the cast alloy is much stronger and harder than that of the bulk material. This has a detrimental effect on tool wear and can result in a substantial worsening of surface quality and dimensional accuracy.

The hardness and tensile strength of cast parts are generally lower than rolled or drawn products of the same composition, with elongation values varying within a broad band. If the SchruppwerkzeugRough form tool casting skin is ignored, it is generally the case that casting alloys are more readily machinable than wrought alloys because of their microstructure. Fig. 17: Standard part used in the ASTM E618 test and the position of the form tool. For the tests performed on copper alloys, the diameter of the bar stock was reduced to 19 mm and the geometry of the part adjusted accordingly. This is permitted under ASTM E618 if the modification is Microstructure inhomogeneities, pores made for all the materials being compared. [1] and non-metallic inclusions all create

24 | DKI Monograph i.18

© WZL/Fraunhofer IPT Seite 18 additional dynamic loads at the tool’s zinc alloys insensitive to stress corro- grades exhibit a certain degree of cutting edge and this can cause edge sion cracking; improving the material’s microstructural inhomogeneity, which chipping or frittering and significant elastic properties without any reduc- to a small extent has a favourable reductions in tool life. Hard inclusions tion in strength. effect on chip formation and a unfa- of aluminium oxide (corundum, spi- vourable influence on tool life. While nel), silicon carbide, silicides, such as Due to the relatively low modulus of the differences are not large, oxygen- iron silicide, or quartz are particularly elasticity of copper alloys, parts ex- free coppers tend to exhibit a greater unwelcome when machining. Porosity, hibiting high resilience after under- degree of ‘stickiness’, making oxygen- e.g. gas porosity caused by small cavi- going major cold forming should be bearing coppers generally preferable ties or voids, can also have a similarly processed in machines that operate for machining purposes. negative impact on tool wear, but the without any play. If necessary, the effect is likely to be less pronounced workpiece has to be supported. In Chip formation can be improved by than that due to repeatedly inter- view of particularly pronounced strain adding chip-breaking elements such as rupted cutting. hardening that copper-based materials lead, sulphur, tellurium and selenium. undergo, they should, whenever pos- The chips break into fine needle-like The cold working of copper alloys leads sible, be machined in their hardened fragments that are ejected from the to greater material hardness and ten- state. This is in fact one of the reasons cutting zone. In Germany the prefer- sile strength and a reduction in elonga- why large differences in machinability red alloys are CuSP with 0.2–0.7 % S tion. These changes in the mechanical are sometimes observed for the same and CuTeP with 0.4–0.7 % Te, whereas properties have a favourable effect material. internationally CuPb1P with 0.7–1.5 % on machinability. In particular, these lead has established itself as the alloy materials show better chip breaking Machining of age hardenable (precipi- of choice. The addition of tellurium characteristics than materials that have tation hardenable) copper alloys is best reduces the electrical conductivity only not been strain hardened through cold carried out on the cold-formed mate- by about 5–8 %. These alloys are used forming. rial prior to precipitation heat treat- for electrical engineering applications ment, as cutting tool wear would be that require materials with both Cold forming of wrought alloys can too great after hardening has occurred. good electrical conductivity and good produce strain within the material, as The only operations favoured when the machinability. the forming process frequently only material is in its precipitation harden- affects a portion of the material’s ed state are grinding and polishing. As even traces of tellurium can sub- crosssection. For instance, when cold To prevent material hardening due to stantially lower the hot forming prop- drawing a rod, the outer layers of high cutting temperatures, cutting flu- erties of copper alloys, it is important the material are subjected to tensile ids should be used to ensure adequate to prevent chips of CuTeP mixing with stresses while the bulk of the material cooling and lubrication. other copper chips. The same applies is in compression. A similar situation to CuSP, as sulphur impurities have a is found in cold skin-rolled semi-fin- detrimental effect on the cold forming ished stock. Completely removing the 4.4 Alloying elements and their capacity of copper alloys. outer layers of the material, as occurs effect on machinability in turning, may in some cases result in Pure copper is difficult to machine be- In terms of chip formation and tool a lengthening of the rod. Conversely, cause of its high ductility and high cold life, alloys of copper with zinc, tin, milling slots, grooves or keyways, or workability. Tool wear is very high and nickel and aluminium show machining indeed performing any other ma- chip formation very poor. As chip com- characteristics similar to those of pure chining operation that removes only pression is substantial, the cutting copper, provided that the microstruc- a part of a material layer, can cause edge is subjected to large mechanical tures of these alloys are composed of twisting or bending of the workpiece. loads. The long tubular chips that form homogeneous mixed crystals (solid Difficulties of this nature can also arise when pure copper is machined are solutions). when processing non-circular tubing, difficult to handle and remove. As the e.g. in form turning, or when planing cutting pressure remains uniform when Quite different machining properties or milling cold-rolled sheet. machining pure copper, chatter marks are shown by heterogeneous cop- tend not to form. There is however a per alloys that do not contain any Deficiencies of this kind can, however, risk of built-up edge formation when chip-breaking elements. The group of be eliminated by subjecting the ma- machining pure copper and this can heterogeneous copper alloys consists chined parts to stress-relief annealing lead to a poor machined finish. The of copper-based alloys containing the for about one hour. Copper can be tendency to form a built-up edge de- elements zinc, tin, nickel or aluminium treated at a temperature between 150 creases with increasing cutting speed at concentrations so high that a second and 180°C, while copper-zinc alloys are and greater feed rates. mixed crystal is formed. The second treated between 250 and 300°C. This mixed crystal, which is usually harder sort of heat treatment is equivalent to As copper oxide does not dissolve in and more brittle than the primary the procedure used to make copper- copper, the oxygen-bearing copper mixed crystal, causes an increase in

DKI Monograph i.18 | 25 the tensile strength and hardness of strength and impact-resistant copper- or ‘hot working brasses’) that con- the alloy at the expense of its elon- aluminium alloys. tain between 54 and 63 % of copper. gation and formability, particularly its In their soft state, the single-phase cold workability. In this regard here, Lead-bearing copper alloys are only of α-brasses behave similarly to pure mention should also be made of the limited applicability if the workpiece copper in terms of chip formation and multi-component copper alloys that undergoes subsequent soldering or tool life. The hardness and tensile contain more than two alloying com- welding. The same applies to work- strength of these materials increases ponents. pieces that, in addition to being with rising zinc content or through cold machined, are also subjected to work hardening, leading to a slight The machinability of heterogeneous extensive cold forming operations. improvement in machinability. (i.e. two-phase or multiphase) copper alloys is significantly better than that Alloys containing chip-breaking addi- Better machinability is shown by het- of the homogeneous single-phase tives form fine, needle-like chips or erogeneous copper-zinc alloys, such as copper alloys. In alloys with low discontinuous chips. The manner in CuZn40. The so-called special brasses, elongation, such as the cast copper-tin which chips are formed when machin- i.e. copper-zinc alloys that contain alloys, the chips break to form short ing leaded copper alloys makes them other elements except lead, also show spiral chips. In alloys exhibiting high more susceptible to chatter marks than somewhat better machining properties elongation, such as CuZn40Mn2, the lead-free copper alloys of the same than the single-phase α-brasses. This chips formed are either short spiral tensile strength. This can be counter- is particularly true of chip formation, chips or long cylindrical chips depend- acted by using machines that operate though tool life is effected negative- ing on the feed rate deployed, with without any play and by using tools ly due to the presence of the harder the latter being formed at low feeds. and tool holders of sufficient rigidity. components of the second mixed On the other hand, the cutting forces crystal (tin, aluminium, nickel, silicon, The process of chip formation can lead that need to be applied when machin- manganese). to tool vibrations, which, if of large ing leaded copper alloys are low, as enough amplitude, can cause chatter can be seen in Table 3. The excellent Optimal machining properties in terms marks on the workpiece. This can be machinability of leaded copper alloys of chip formation (see Fig. 18c) and counteracted by using tools and tool is attributable to the ease with which tool life are shown by the so-called holders of maximum stiffness and the material can be broken into tiny leaded brasses, i.e. (α+β)-copper-zinc minimizing tool overhang. fragments. In addition to the low cut- alloys that contain added lead. For ting forces, the service life of the cut- turning operations, particularly those The machinability of heterogeneous ting tools are also longer, being limited carried out on automatic screw machin- two-phase copper alloys is reduced as only by the average flank wear. es, the alloys with the best machin- a result of the presence of the second ability are CuZn39Pb3 and CuZn40Pb2. harder mixed crystal. Increasing tin It should, however, also be recalled content, e.g. in copper-tin casting that fine needle-like chips can be Lead is practically insoluble in the alloys, causes a drop in cutting speed disadvantageous as they can block copper-zinc alloy, and when finely for the same tool life. Aluminium and the cutting fluid filters. Copper alloys dispersed it acts as an excellent chip larger quantities of iron and nickel also that produce longer chips may also breaker and in some cases even as have a detrimental effect on the ma- be preferable when drilling, as this a friction-reducing lubricant. A lead chinability of copper alloys. The ma- chip form is easier to remove from the content greater than 3.5 % is uncom- chining properties of multi-component drilled hole. mon, as it then becomes too difficult copper-aluminium alloys approach to achieve a highly dispersed distri- those of steel. In what follows, we shall take a closer bution of the lead within the copper- look at the machinability of the indi- zinc alloy. The small improvement in As already discussed for pure copper, vidual groups of copper alloys in order machinability that could be achieved if chip-breaking additives can increase to better understand why copper alloys higher lead concentrations were used the machinability of copper alloys. The are classified into three main machin- does not provide sufficient justification sole chip-breaking alloying element ability categories. for accepting the associated deterio- used in copper alloys is lead. Add- ration in mechanical properties. For ing lead to the alloy has only a minor In the case of copper-zinc alloys (i.e. brasses that will not only be machin- effect on the material’s mechanical the brasses), a distinction is made bet- ed, but will also undergo cold or hot strength. However, the ability of the ween the single-phase solid-solution forming, the lead content is limited to alloy to undergo cold forming and its α-copper-zinc alloys (also known as about 1.5 %. Too high a concentration ability to withstand impact and shock ‘alpha brasses’ or ‘cold working of lead also impairs polishability. are both reduced significantly. For brasses’), which contain at least 63 % these reasons and particularly because of copper, and the heterogeneous Further the European Directive 2000/53/EC the hot forming properties are im- two-phase (α+β)-copper-zinc alloys restricts the use of automobile com- paired, lead is not added to high- (‘alpha-beta brasses’, ‘duplex brasses’ ponents containing heavy metals and

26 | DKI Monograph i.18 the EU Directive 2002/95/EC rules the promote tool wear so that compared α-mixed crystals. Like other single- lead content in electrical and electronic with other copper alloys the cutting phase copper-based materials, these equipment. However an exemption speed has to be reduced. alloys are difficult to machine as they rule applies to copper-based materials tend to produce long, ductile chips. that allow a maximum lead content The cast copper-tin-zinc alloys have Better machinability is exhibited by of 4 percent by weight. The European a heterogeneous microstructure and the two-phase aluminium bronzes and Directive 98/83/EC states that plumbing those that contain added lead also multi-component aluminium bronzes. materials must release no more than exhibit good machinability. The same However, because of their high tensile 25 µg of lead (Pb) per litre of drinking applies to the leaded cast copper-tin strength and hardness these materials water, and as of 2013, no more than alloy CuSn11Pb2-C. These materials are cause substantial tool wear. Compared 10 µg Pb/l will be permitted. solid lubricants to which the added with cast copper-tin bronzes, an alloy lead content may significantly exceed such as CuAl10Fe5Ni5-C has to be ma- Efforts to find a suitable element to 3 % in order to achieve the desired chined at a much lower cutting speed replace lead as an additive in copper- lubrication and casting properties. to maintain the same tool life. Silicon- based alloys led to the development bearing copper-aluminium alloys, such of a lead-free silicon-bearing copper Machinability that is as good or better as CuAl7Si, may contain hard inclusions alloy for use in sanitary fittings. The is exhibited by the heterogeneous cast of iron silicides as a result of contam- machinability of this material is at a leaded tin bronzes that contain up to ination with iron. Carbide tools are level comparable to that of the leaded 26 % of added lead to improve lubri- therefore recommended when machin- brasses (Fig. 18b; machinability group I). cation properties. ing this type of material. The machin- The silicon-rich phases in the micro- ability of the heterogeneous two-phase structure (kappa phases) act as chip The strengthening influence of nickel aluminium bronzes is more like that of breakers. Compared to lead, these in heterogeneous but lead-free cop- medium-hard steel grades than that of phases are ‘hard’ chip breakers [20]. per-nickel-zinc alloys (nickel silvers) other copper-based materials. As the silicon increases the strength of also tends to reduce tool life. the material and the κ-phase acts as In contrast, the machinability of lead- an abrasive, tool wear is greater than ed nickel silvers is almost as good as when machining leaded alloys. that of the free-cutting brasses. Tool lives, however, are significantly shorter In copper-tin alloys (i.e. the ‘tin due to the greater hardness of the bronzes’) the boundary between nickel silvers. homogeneous single-phase and heterogeneous two-phase alloys lies The single-phase copper-nickel alloys at around only 8 %. Nevertheless, the are extremely difficult to machine due two-phase cast tin bronzes with higher to their strong propensity to form burrs tin content also tend to be less easy and very long, ductile chips. to machine when assessed in terms of tool wear and chip formation (Fig. Copper-aluminium alloys (‘aluminium 18a). And while cast tin bronzes are bronzes’) exhibit a homogeneous sin- more machinable than single-phase gle-phase micro-structure up to about wrought bronzes, the increase in ten- 8 % aluminium. The microstructure of sile strength and hardness that accom- single-phase binary copper-alumin- panies increasing tin content tends to ium alloys consists of relatively soft

a b c

CuSn8P CuZn21Si3P CuZn39Pb3 f=0,12 mm ap=1 mm Mineral oil ISO VG 15

Fig. 18 Chip forms

DKI Monograph i.18 | 27 4.5 Classification of copper and cold form. The greater cold formability copper alloy with a lead content below copper alloys into main of type II copper alloys means that they the maximum permissible limit depends machinability groups generally produce longer chips than on the actual concentration of lead in Copper and copper alloys are con- the type I alloys. the alloy. Under certain conditions, the ventionally classified into three main lead content may justify reclassifying machinability groups, with each main Machinability group III a type II copper alloy as type I or vice group containing materials of similar (‘Type III’ or ‘long-chip’ alloys) versa. machinability. The broad classifica- This group contains those copper-based tion into the three main machina- materials that are harder to machine In each of the three main machinability bility groups is based on estimations than the alloys in groups I and II. The groups a distinction is made between of the assessment criteria discussed single-phase microstructures of these wrought and cast alloys. The machin- in Section 3. For copper and copper materials and their excellent cold workability of the copper alloys can vary alloys, the main machinability criteria ability result in higher cutting forces significantly, even between materials of relevance are chip form and wear. and long, ductile chips. The excellent in the same machinability group. The In addition to the attributes chip form cold forming properties of low-alloyed tables have been supplemented by and tool wear, micro-structure is also copper-based alloys seriously impair machinability ratings for the individual used to assist classification as it too chip formation and result in accelerated alloys (see earlier discussion). These has a significant influence on a mate- tool wear. Homogeneous (i.e. single- ratings enable the materials within a rial’s machinability. Table Table 8 lists phase, solid-solution) copper alloys main group to be distinguished more the attributes used to classify copper containing zinc, tin, nickel or alumin- precisely. The machinability ratings of and copper alloys into the three main ium also exhibit poor chip forming the alloys in group I range from 100 to machinability groups. qualities and low tool lives. Type III 70, those in group II vary from 60 to 40, materials also include heterogeneous while the materials in group III exhibit Machinability group I alloys such as the high-strength copper- machinability ratings from 30 to 20. The (‘Type I’ or ‘free-cutting’ alloys) aluminium alloys and the low-alloyed, machinability rating is based partly on This group includes copper-based strain-hardened copper alloys. experimental evidence and partly on materials containing added lead, tel- experience. It is important to realize lurium or sulphur with a homogeneous Tables Table 9, Table 10 and Table 11 that the machinability ratings listed or heterogeneous microstructure. The present the conventional classification were determined using a variety of excellent machinability of the type of standardized copper and copper alloy different constraints and criteria. There I materials is due to the addition of materials into the machinability groups is therefore a degree of uncertainty and these chip-breaking elements. I, II and III respectively. Classification imprecision associated with the quoted was based primarily on expected rating values and with their applicability Machinability group II chip formation, though for a number to a particular machining situation. In (‘Type II’ or ‘short-chip’ alloys) of hard-to-machine type III alloys, turning work, the applicability of the Type II copper alloys are mostly lead- classification was based on the more rating figures is estimated to be around free and exhibit moderate to good ma- pronounced tool wear. 70 %. chinability. They are generally harder than type I materials with a heteroge- As chip formation is strongly dependent neous microstructure and are easier to on lead content, the machinability of a

Attributes Machinability group

I II III (Type I Alloys) (Type II Alloys) (Type III Alloys) Microstructure homogeneous/heterogeneous Heterogeneous a) homogeneous structure with chip-breaking (coarse particulate phase) b) heterogeneous particles (Pb, S, Te) no Pb particles (finely dispersed deposits)

Chip form short medium length long and ductile (tightly coiled (discontinuous, brittle chips) (coiled cylindrical chips) cylindrical, tangled or ribbon chips) Tool wear low medium high

Cold workability of generally poor generally good a) very good wrought materials b) low Hot workability of generally good moderately good a) moderately good wrought materials b) good

Table 8: Conventional scheme for classifying the machinability of copper and copper alloys

28 | DKI Monograph i.18 Material 0,2% yield Tensile Elongation Tool strength Hardness Machinability Alloy group I strength R after frac- geometry Designation Number Number m R [HB] rating [N/mm2] p0,2 ture A [%] designator (EN) (UNS) [N/mm2] Low-alloyed CuPb1P CW113C C18700 - 80 copper alloys – non- age-hardenable CuSP CW114C C14700 250 – 360 200 - 320 5 - 7 90-110 C* 80

CuTeP CW118C C14500 C* 80 Copper-nickel-zinc CuNi7Zn39Pb3Mn2 CW400J - 510 - 680 400 -600 5 - 12 150 - 200 - 90 alloys CuNi10Zn42Pb2 CW402J C79800 510 - 590 350 - 450 5 - 12 160 - 190 A / A* 80

CuNi12Zn30Pb1 CW406J C79300 420 - 650 280 - 600 8 - 20 130 - 180 A / A* 70 Copper-tin-zinc CuSn4Zn4Pb4 CW456K C54400 450 - 720 350 - 680 10 150 - 210 - 80 alloys

Copper-tin alloy CuSn5Pb1 CW458K C53400 450 - 720 350 - 680 10 150 - 210 - 70

Leaded binary CuZn35Pb2 CW601N C34200 330 - 440 150 - 340 14 - 30 90 - 130 A 90 copper-zinc alloys CuZn36Pb2As CW602N C35330 280 - 430 120 - 200 15 - 30 80 - 110 - 80

CuZn36Pb3 CW603N C35600 340 - 550 160 - 450 8 - 20 90 - 150 A 100

CuZn38Pb1 CW607N C37000 A 80 Wrought copper alloys alloys copper Wrought CuZn38Pb2 CW608N C37700 A 90 360 - 550 150 - 420 8 - 25 90 - 150 CuZn39Pb0,5 CW610N C36500 A 70

CuZn39Pb2 CW612N - A 90

CuZn39Pb3 CW614N C38500 A 100 360 - 550 150 - 420 8 - 20 90 - 150 CuZn40Pb2 CW617N C37700 - 90

CuZn43Pb2Al CW624N - as fabricated - 80 Multi-component CuZn40Mn1Pb CW720R - 390 - 560 200 - 500 10 - 20 110 - 160 A 60 copper-zinc alloys CuZn21Si3P CW724R C69300 530 - 700 300 - 450 10 - 20 - 80* Copper-tin casting alloy CuSn11Pb2-C CC482K - 240 - 280 130 - 150 5 80 – 90 A 70

Copper-tin and CuSn3Zn8Pb5-C CC490K - 180 - 220 85 - 100 12 - 15 60 - 70 A 90 copper-tin-zinc casting alloys CuSn3Zn9Pb7-C - C84400 200 - 234 - 16 - 26 55 - 90

CuSn5Zn5Pb5-C CC491K C83600 180 - 220 85 - 100 12 - 15 60 - 70 A 90

CuSn7Zn4Pb7-C CC493K C93200 230 - 260 120 12 - 15 60 - 70 A 90

CuSn5Zn5Pb2-C CC499K - 200 - 250 90 - 110 6 - 13 60 - 65 - 90 Copper-lead and CuPb10Sn10-C CC495K C93700 180 - 220 80 - 110 3 - 8 60 - 70 A 90 copper-tin casting

Copper casting alloys alloys casting Copper alloys CuSn7Pb15-C CC496K CC93800 170 - 200 80 - 90 7 - 8 60 - 65 A 90 Copper-zinc casting CuZn33Pb2-C CC750S - 180 70 12 45 - 50 A 80 alloys CuZn39Pb1Al-C CC754S - 220 - 350 80 - 250 4 - 15 65 - 110 - 80

CuZn16Si4-C CC761S C87800 400 - 530 230 - 370 5 - 10 100 - 150 A* 70* * the use of a cutting tool with a chip breaker is recommended

Table 9: Machinability classification of standardized copper-based materials Machinability group I: Copper-based materials with excellent machining properties

DKI Monograph i.18 | 29 Material Tensile 0,2% yield Elongati- Tool strength strength on after Hardness Machinability Alloy group II geometry Designation Number Number R R fracture [HB] rating m p0,2 designator (EN) (UNS) [N/mm2] [N/mm2] A [%] Low-alloyed copper alloys, hardenable CuNi2SiCr – C81540 – – –– – 40* in cold-worked and precipitation- CuNi3Si1 CW112C C70250 700 - 800 630 - 780 10 180 - 200 A* 40* hardened state Copper-nickel-zinc CuNi18Zn19Pb1 CW408J C76300 420 - 650 280 - 600 8 - 20 130 - 180 A / A* 60 alloys Binary copper-zinc CuZn40 CW509L C28000 340 260 25 80 A* 40 alloys Leaded binary copper- CuZn37Pb0,5 CW604N C33500 300 - 440 200 - 320 10 - 45 55 - 115 A 60 zinc alloys Multi-component CuZn31Si1 CW708R C69800 460 - 530 250 - 330 12 - 22 115 - 145 A* 40 copper-zinc alloys

CuZn35Ni3Mn2AlPb CW710R – 490 - 550 300 - 400 10 - 20 120 - 150 A* 50 Wrought copper alloys alloys copper Wrought CuZn37Mn3Al2PbSi CW713R – 540 - 640 280 - 400 5 - 15 150 - 180 A / A* 50

CuZn38Mn1Al CW716R – 210 - 280 – 10 - 18 120 - 150 A* 40

CuZn39Sn1 CW719R C46400 340 - 460 170 - 340 12 - 30 80 -145 A* 40

CuZn40Mn2Fe1 CW723R – 460 - 540 270 - 320 8 - 20 110 – 150 A* 50

Copper-aluminium CuAl10Ni3Fe2-C CC332G – 500 - 600 180 - 250 18 - 20 100 – 130 C* 50 casting alloys

CuAl10Fe5Ni5-C CC333G C95500 600 - 650 250 - 280 7 - 13 140 – 150 – 50

Copper-tin casting CuSn12-C CC483K C90800 260 - 300 140 - 150 5 - 7 80 - 90 A* 50 alloys

CuSn12Ni2-C CC484K C91700 280 - 300 160 - 180 8 - 12 85 - 95 A 40

Copper-zinc casting CuZn32Al2Mn2Fe1-C CC763S – 430 - 440 150 - 330 3 - 10 100 - 130 A* 40* alloys

CuZn34Mn3Al2Fe1-C CC764S – 600 - 620 250 - 260 10 - 15 140 - 150 A* 40* Copper casting alloys casting Copper

CuZn37Al1-C CC766S – 450 170 25 105 A* 40

CuZn38Al-C CC767S – 380 130 30 75 A* 40

* the use of a cutting tool with a chip breaker is recommended

Table 10: Machinability classification of standardized copper-based materials Machinability group II: Copper-based materials with good to moderate machining properties

30 | DKI Monograph i.18 Alloy group III Material Tensile 0,2% Elonga- Hardness Tool Machi- strength Yield tion [HB] geo- nability Designation Number Number R strength after metry rating (EN) (UNS) m Rp0,2 fracture desig- [N/mm2] [N/mm2] A [%] nator Copper Cu-OFE CW009A C10100 200 - 350 120 - 320 5 - 35 35 - 110 C* 20 CuAg0,10 CW013A C11600 200 - 350 120 - 320 5 - 35 35 – 100 C* 20 CuAg0,1P CW016A - C* 20 260 220 - 12 Cu-HCP CW021A - C* 20 Cu-DHP CW024A C12200 200 - 350 80 - 330 5 - 35 35 - 110 C* 20 Low-alloyed copper alloys, CuBe1,7 CW100C C17000 - - -- A 20 harde-nable, solution- CuBe2 CW101C C17200 1150 - 1300 1000 - 1150 2 320 - 350 A 30 annealed, cold-worked and CuCo2Be CW104C C17500 700 - 800 630 - 730 5 200 - 220 A 30 precipitation-hardened CuCr1Zr CW106C C18150 400 - 470 310 - 380 8 - 12 135 - 180 A* 30 CuNi1Si CW109C - 500 - 590 420 - 570 10 - 12 140 - 160 A* 30 CuNi2Be CW110C C17510 700 - 800 630 - 730 5 200 - 220 – 30 CuNi2Si CW111C C64700 550 - 640 430 - 620 10 155 - 180 B* 30 CuZr CW120C C15000 280 - 350 180 - 260 18 - 20 90 - 130 – 20 Low-alloyed copper alloys, CuBe2 CW101C C17200 580 - 650 450 - 500 8 - 10 155 - 240 B / B* 20 harde-nable, solution- CuCo2Be CW104C C17500 400 - 500 330 - 430 8 - 10 110 - 175 B 30 annealed, cold-worked CuNi1Si CW109C 300 - 410 210 - 320 9 - 16 85 - 150 B* 20 CuNi2Si CW111C C64700 320 - 410 230 - 370 8 – 15 90 - 165 A* 30 CuNi3Si1 CW112C C70250 450 - 580 390 - 550 8 - 10 135 - 210 A 30 Low-alloyed copper alloys, harde-nable, solution- CuCr1Zr CW106C C18150 200 60 30 65 - 90 B* 20 annealed Low-alloyed copper alloys – CuSi3Mn1 CW116C C65500 380 - 900 260 - 890 8 - 50 85 - 210 - 30 non-age-hardenable CuSn0,15 CW117C C14200 250 - 420 320 - 490 2 - 9 60 - 120 - 20 Copper-aluminium alloys CuAl10Fe3Mn2 CW306G - 590 - 690 330 - 510 6 - 12 140 - 180 - 30 CuAl10Ni5Fe4 CW307G C63000 680 - 740 480 - 530 8 - 10 170 - 210 - 30 Copper-nickel alloys CuNi25 CW350H C71300 290 100 - 70 - 100 - 20

Wrought copper alloys copper Wrought CuNi10Fe1Mn CW352H C70600 280 - 350 90 - 150 10 - 30 70 - 100 A / A* 20 CuNi30Mn1Fe CW354H C71500 340 - 420 120 - 180 14 - 30 80 - 110 A / A* 20 Copper-nickel-zinc alloys CuNi12Zn24 CW403J C75700 380 - 640 270 - 550 5 - 38 90 – 190 A / A* 20 CuNi18Zn20 CW409J - 400 - 650 280 - 580 11 - 35 100 - 210 A / A* 20 Copper-tin alloys CuSn4 CW450K C51100 320 - 450 140 - 160 55 80 – 130 - 20 CuSn5 CW451K C51000 330 - 540 220 - 480 20 - 45 80 - 170 - 20 CuSn6 CW452K C51900 340 - 550 230 - 500 4 - 35 15 - 45 A* 20 CuSn8 CW453K C52100 390 - 620 260 - 550 15 - 45 90 – 190 A* 20 CuSn8P CW459K - 390 - 620 260 - 550 15 - 45 90 – 190 A* 30 Binary copper-zinc alloys CuZn5 CW500L C21000 240 - 350 60 - 310 15 - 30 55 – 115 A* 20 CuZn10 CW501L C22000 270 - 380 80 - 350 14 - 28 60 – 125 A* 20 CuZn15 CW502L C23000 290 - 430 100 - 390 12 - 27 75 - 135 A* 30 CuZn20 CW503L C24000 300 - 450 110 - 410 10 - 27 80 – 140 B* 30 CuZn28 CW504L - B* 30 CuZn30 CW505L C26000 310 - 460 120 - 420 10 - 27 85 – 145 B* 30 CuZn33 CW506L C26800 B* 30 CuZn36 CW507L C27200 A / B* 30 310 - 440 120 - 400 12 - 30 70 - 140 CuZn37 CW508L C27400 A / B* 30 Multi-component copper- CuZn20Al2As CW702R C68700 340 – 390 120 - 150 40 - 45 65 - 95 A 30 zinc alloys CuZn28Sn1AS CW706R C44300 320 - 360 100 - 140 45 - 55 60 - 110 A* 30 Copper-aluminium CuAl10Fe2-C CC331G C95200 500 - 600 180 - 250 15 - 20 100 – 130 B* 20 casting alloys Copper-nickel CuNi10Fe1Mn1-C CC380H C96200 280 100 - 120 20 - 25 70 A* 20 casting alloys CuNi30Fe1Mn1NbSi-C CC383H C96400 440 230 18 115 A* 20 Copper-zinc CuZn25Al5Mn4Fe3-C CC762S C86100 440 450 - 480 5 - 8 180 - 190 A* 30*

Copper casting alloys casting Copper casting alloys

* the use of a cutting tool with a chip breaker is recommended

Table 11: Machinability classification of standardized copper-based materials Machinability group III: Copper-based materials with moderate to poor machining properties

DKI Monograph i.18 | 31 5 Cutting-tool materials

The principal tool materials used to ma- j) HS2-9-1 1.3346 material. For these applications, high- chine copper-based materials are high- k) HS2-9-2 1.3348 speed tool steels produced by powder speed steels (HSS), cemented carbides l) HS6-5-3 1.3344 metallurgical methods are preferred. and synthetic diamond. Plain carbon m) HS6-5-2C 1.3343 tool steels play no role in this field. Cobalt (Co) is sometimes added to these 5.2 Carbides steels to improve their hot hardness Carbides are sintered composite ma- 5.1 High-speed steel and their tempering resistance, while terials comprising a metallic binder High-speed steels (HSS) are highly alloy- vanadium (V) is added to increase (typically cobalt) into which the car- ed tool steels. High-speed steels differ resistance to wear. A number of these bides (WC, TiC, TaC, etc.) are embedded. from other types of steel in that they steels, such as HS6-5-2C (material no. The function of the binder is to bind contain a high concentration of carbides 1.3343) have a higher carbon content in the brittle carbide particles together that gives these materials a relatively order to lengthen tool life. to form a relatively strong solid. The high resistance to wear and good hot function of the carbides is to create a hardness. The main alloying elements The high-speed steel HS10-4-3-0 (ma- material with a high hot hardness and are tungsten, molybdenum, vanadium, terial no. 1.3207; see above list) can be wear resistance. cobalt and chromium. The hardness of recommended for many applications as the high-speed steels is influenced by it exhibits high hot hardness and good Copper alloys are machined using tools both the hardness of the base material wear resistance and therefore pro- made from uncoated WC-Co cemented – the martensite – and the presence of longed tool life. However, a different carbides or using coated carbide tools. the carbides. The tempering resistance HSS should be selected if the machin- Straight two-phase WC-Co carbides of HSS is determined by the alloying ing process or tool geometry requires a consist exclusively of hard grains of elements dissolved in the matrix. cutting-tool material of greater tungsten carbide (WC) embedded in toughness. The toughest of the con- the cobalt (Co) binder. In the alloy- High-speed steels are designated in ventional high-speed steels is the alloy ed WC-Co carbides part of the WC is accordance with an established scheme: HS2-9-1 (material no. 1.3346), which replaced by vanadium carbide (VC), They are identified by the initials “HS” is why small twist drills, end milling chromium carbide (Cr3C2) or tantalum/ followed by the percentage content of cutters, etc. are frequently manufac- niobium carbide ((Ta,Nb)C). WC-Co tungsten, molybdenum, vanadium and tured from this or a similar HSS. Milling carbides are characterized by high cobalt. For example, the tool steel cutters and counterbores are produced abrasion resistance. The various grades HS18-1-2-10 contains 18 % W, 1 % Mo, primarily from HS6-5-2 (material no. of WC-Co carbides available differ in 2 % V and 10 % Co. Designations such as 1.3243), reamers are generally made the relative content of cobalt binder “HSS”, “HSS-Co” or other manufacturer- from HS6-5-3 (material no. 1.3344). and the size of the tungsten carbide specific designations are of little value grains. With increasing cobalt content, unless the composition of the HSS grade In addition to the high-speed steels the toughness of the cemented carbide is unambiguously stated. produced by conventional metallurgi- rises at the expense of hardness and cal processes, HSS materials produced wear resistance. The uncoated carbides The conventionally produced high- by powder metallurgy (PM) are also used for finishing and semi-roughing speed tool steels that are used for available commercially. Compared with operations typically contain about machining copper and copper alloys are conventionally produced HSS materials, 6 % w/w of cobalt (WC-6Co). Tougher divided into the high tungsten-alloyed those produced by PM generally exhibit cemented carbides with a higher cobalt steels, with tungsten concentrations of a greater degree of alloying. Because of content (e.g. WC-9Co) are used for above 12 %: the much finer distribution of carbide roughing operations or interrupted particles within the microstructure, PM cuts. Designation in acc. HSS alloys have a considerably better with DIN EN ISO 4987 No. cuttingedge hardness than HSS types In terms of WC grain size, a distinction produced by conventional metallurgi- is made between the conventional fine a) HS18-1-2-10 1.3265 cal techniques. They are also easier to grain carbides with an average grain b) HS18-1-2-5 1.3255 grind due to their finer grain structure size of 0.8–1.3 µm, the finest grain c) HS18-0-1 1.3355 and the absence of segregation streaks. carbides (0.5–0.8 µm) and the ultrafine d) HS12-1-4-5 1.3202 Both of these factors help to improve grain carbides (0.2–0.5 mm). e) HS12-1-4 1.3302 tool life when performing difficult ma- If the cobalt binder content remains f) HS12-1-2 1.3318 chining operations, such as tapping, constant, decreasing the WC grain size profile reaming, gear hobbing and leads to an increase in hardness and and the molybdenum-alloyed steels: gear shaping. The edge strength of the transverse rupture strength. High-qual- cutting material is an important factor ity finest grain and ultrafine grain car- g) HS10-4-3-10 1.3207 in such operations as chip flow is often bides exhibit superior hardness, edge h) HS2-9-1-8 1.3247 restricted or because the cutting edge strength and toughness compared with i) HS6-5-2-5 1.3243 engages very suddenly with the work conventional fine grain carbides [21].

32 | DKI Monograph i.18 These high-performance carbides are materials. Carbides in the application Coated tools show reduced wear typically used for the production of groups N15–N20 are preferred if the because of increased wear resistance forming tools such as drills or end mill- machining operation requires a tool and reduced interfacial adhesion. ing cutters. Cutting inserts for turning material with enhanced toughness, They also act as a diffusion barrier and operations are usually made from fine such as when turning with geome- improve the tool’s thermal and chemi- grain carbide with a grain size greater trically complex tools, or when the cal stability. The coatings used with the than 0.8 mm. turning method produces an uncut cutting materials in main group N in- chip of large area, or in uninterrup- clude TiAlN, TiN, AlCrN, CrN, AlTiCrN, DLC According to the DIN ISO 513 standard, ted cutting. Compared with the N10 (a-C:H, a-C:Me) and diamond coatings. copper-based work materials are in carbides, the N15-N20 carbides have a main application group ‘N’ (see Fig. 19). higher cobalt content and are corre- Each of the main application groups spondingly tougher. 5.3 Diamond as a cutting material (DIN ISO 513 distinguishes a total of six Diamond is composed of pure carbon main groups) is further divided into and is the hardest of all known ma- application groups (see Fig. 19). The Coatings terials. However, its extreme hardness number after the letter ‘N’ indicates The performance of (cemented carbide) makes it very brittle and therefore very the toughness and wear resistance of cutting tools can be further improved sensitive to impact and thermal stress. the cutting-tool material. The higher by coating. Coatings make high-speed These properties effectively define the this number is, the higher the tough- machining possible and can significantly areas in which diamond is applied as ness and therefore the lower the wear extend tool life. Coated carbides were a a cutting material. Both natural and resistance of the cutting material. milestone in the development of cutting synthetic diamonds are used in machin- Carbide manufacturers assign their tools that were both tough and wear- ing operations. Both monocrystalline different carbide grades to one or more resistant. The most-important coating (DIN ISO 513 code: DM) and polycrystal- suitable application groups depending materials are titanium carbide (TiC), tita- line diamond (DIN ISO 513 code: DP) on the particular properties of the nium nitride (TiN), titanium aluminium are used. The abbreviation PCD is also individual coated or uncoated carbide. nitride (TiAlN), aluminium oxide (Al2O3), frequently used when referring to tools Uncoated and coated carbides are titanium carbonitride (TiCN), diamond- manufactured from polycrystalline Abb. 19: Hauptanwendungiven the letter codeg designationss gru pp ‘HW’ e likeN carbon der (DLC) harten and diamond. BySchneidstoffe vary- diamond. nach DIN ISO 513 and ‘HC’ respectively. Examples of such ing the coating material, the structure designations are: HW-N10 or HC-N20. of the coating layer, its thickness and Monocrystalline diamonds are par- the coating method used, the properties ticularly well-suited for precision Carbides in application group N10 of the coated material can be adjusted machining operations and are widely exhibit the broadest application to suit the requirements of a specific applied in the field of ultra-precision range when machining copper-based machining task. machining.

HaupMaintanwendun applicationg groupssg ru ppen AnwendunApplicationgs groupsg ru ppen

KennCode- letter ColourKenn code- WerkstückWorkpiece-Werkstoff material HardHarte cutting materials buchstabe farbe Schneidstoffe

Nichteisenmetalle:Non-ferrous metals: N01N01 N05N05 aluminium and other N10 N green Aluminium und N10 N 15 N Grün non-ferrous metals, N20 N15 andere Nichteisenmetalle, N20 N25 non-metal materials N30 N25 Nichtmetallwerkstoffe N30

increasingZunehmende cutting speed Schnittgeschwindigkeit, increasingzunehmende wear resistance Verschleißfestigkeit of tool material des Schneidstoffs

increasingZuneh men cutting der speed Vorsc hbhub, increasingzunehmende wear resistance Zähigkeit of tool des material Schneidstoffs

Fig. 19: Main application group N of hard cutting materials (DIN ISO 513)

DKI Monograph i.18 | 33

Quelle:

5.4 Wahl des Schneidstoffs

Die Wirtschaftlichkeit eines Schneidstoffs hängt von mehreren Einflussgrößen ab. Bei einer uneingeschränkten Wahl der Spanungsdicke ergibt sich die schneidspezifische Mengenrate

(d. h. bearbeitete Werkstücke je Zeiteinheit) aus dem Produkt h vc, wobei h die Spanungs-

dicke und vc die anwendbare Schnittgeschwindigkeit bezeichnet.

Soweit größere Zugaben zu spanen sind, tritt als direkter Faktor noch die mögliche Schnitt-

tiefe ap hinzu, die geringfügig vom Schneidstoff beeinflusst wird.

In der überwiegenden Mehrzahl der Bearbeitungsfälle ist die Schnitttiefe ap durch die entsprechende Zugabe fest vorgegeben und die Spanungsdicke h bzw. der Vorschub f entwe- der durch die Starrheit des Systems Maschine/Werkstück/Werkzeug oder bestimmte Forde- rungen an die Rauheit der bearbeiteten Fläche, unabhängig vom Schneidstoff, nach oben begrenzt. In diesen Fällen reduziert sich der Einfluss des Schneidstoffs auf die anwendbare

Schnittgeschwindigkeit vc.

Eine weitere Einflussgröße für die Wahl des Schneidstoffs stellen die Werkzeugkosten je

Standzeit KWT dar. Sie ergeben sich angenähert nach VDI 3321 aus der Gleichung:

KWa KWT = + KWw ()+KWs (22) nT

PCD tools are used both for precision KWw Cost in € associated with chan- same number of parts to be machined machining andworin for roughing bedeuten: operations. ging the worn tool in a faster time. In some applications the rough machining and finishK machiningWT Werkzeugkosten steps can be K Wsje StandzeitC ost in € forin regrinding the tool Such considerations generally lead to combined into Ka Wasingle step Anschaffungskosten [22]. des(not Werkzeugs applicable if indexable in the conclusion that cemented carbide inserts are used) cutting tools (typically, N10 grade car- nT Anzahl der Standzeiten (bei Wendeplatten Anzahl der Schneidkanten) bide) are much more preferable than KWw Kosten für das Wechseln des verschlissenen Werkzeugs in 5.4 Selecting the cutting material Equation 22 shows that the cost of HSS tools. Indeed, carbide can remain KWs Kosten für das Nachschleifen des Werkzeugs (entfällt bei Wendeplatten) in The cost-effectiveness of a cutting ma- purchasing the tool KWa typically the material of choice even when cut- terial depends Dieon several Gleichung factors. If(22) no zeigt,represents dass onlydie aAnschaffungskosten small fraction of the KtingWa speedin der restrictions Regel meannur einen that the relativ restrictions are placed on the thickness total costs KWT associated with the number of parts produced per unit time of the uncut chip,kleinen the number Anteil of der work Werkzeugkosten- service life of the je tool. Standzeit The two otherKWT ausmachen.is no greater Die than beiden that achievable anderen with Sum- 5 Schneidstoffe pieces machinedmanden per unit sindtime dependsmeist größer. terms are generally larger. 52 a HSS tool. This is because the longer on the cutting material used and is service life of a carbide tool allows a given by the product h • vc, where h is The tool costs associated with the pro- greater number of parts to be machin- K 5.4 Wahl des Schneidstoffsthe thickness ofDie the Werkzeugkosten uncut chip and vc is jeduction Werkstück of one partW folgen are therefore dann givender Gleichung ed in one tool life, increasing the value the applicable cutting speed. by the following equation: of nWT in Eq. 23. If indexable cutting K inserts are used, KWs, the third term in If larger amounts of stock are to be K WT Eq. 22, is zero, which reduces the unit Die Wirtschaftlichkeit eines Schneidstoffs hängt von mehrerenW Einflussgrößen= (23) ab. Bei einer (23) removed, depth of cut ap is another nWT production cost given by Eq. 24. uneingeschränkten Wahl derfactor Spanungsdicke that directly influences ergibt tool sich die schneidspezifische Mengenrate (d. h. bearbeitete Werkstückeproductivity je Zeiteinheit) – though one aus that dem is only Produkt where: h v c, wobei h die Spanungs- The factors limiting the application slightly dependentwobei on thebedeuten: choice of tool of carbide as a cutting material dicke und vc die anwendbare Schnittgeschwindigkeit bezeichnet. material. KW T ool costs in € for fabricating are usually related to tool geometry. KW Werkzeugkosten je Werkstückone part in Geometrically complex cutting tools In nearly all practical cases, however, typically have to be made from Soweit größere Zugaben zu spanen sind,nWT tritt Standmenge, als direkter Faktord. h. Anzahl noch dieder möglichepro Standzeit Schnitt- bearbeiteten Werkstücke the depth of cut ap is fixed by the stock nWT Number of parts machined in extremely tough cutting materials. tiefe ap hinzu, die geringfügigallowance, vom Schneidstoff whileDie the vom thickness Schneidstoff beeinflusst of the wird. abhängigen one tool Bearbeitungskosten life je WerkstückCemented carbides K1 sind are dann often unable to uncut chip h and/or the feed f are meet these requirements or the cost of limited by the rigidity of the machine/ The total cost of manufacturing one manufacturing a complex tool shape In der überwiegenden Mehrzahl der Bearbeitungsfälle ist die Schnitttiefe ap durch die ent- workpiece/tool system or by certain K1 =part th1 is R therefore + Kfix +given KW by:= Kth1 + Kfix + KWfrom carbide often (24) proves prohibitively sprechende Zugabe fest vorgegebenspecifications regarding und die the Spanungsdicke roughness h bzw. der Vorschub f entwe- expensive. Tapping is an example of der durch die Starrheit desof Systemsthe machined Maschine/Werkstück/Werkzeug surface, irrespective of K1 = th1 • R + oder Kfix + KbestimmteW = Kth1 + Kfix +Forde- KW (24) a cutting operation that places high the cutting material used. In such cases, demands on the toughness of the tool rungen an die Rauheit derthe bearbeiteten influence of the Fläche, cutting material unabhängig where: vom Schneidstoff, nach oben material, as at the end of the opera- begrenzt. In diesen Fällenis reduziert restricted simply sich derto its Einfluss effect on thedes SchneidstoffsK1 Total fabrication auf die anwendbarecost per unit tion the tap has to be unscrewed from cutting speed vc. product in € the hole. The resulting frictional forces Schnittgeschwindigkeit vc. can generate high tensile stresses Another factor influencing the choice of th1 Machining time per part in at the tool’s cutting edges. Taps are cutting material is the cost per tool life, minutes therefore typically produced in HSS. Eine weitere Einflussgrößewhich für accordingdie Wahl to thedes VDI Schneidstoffs Guidelines stellen die Werkzeugkosten je Standzeit KWT dar. Sie ergeben3321 can sich be approximated angenähert by: nach VDI 3321Kfix aus F ixedder costsGleichung: in € (independent of cutting speed vc)

KWa Kth1 Machining costs in € KWT = + KWw ()+KWs (22) (22)

nT R C ost rate for operator and where: machine (excluding tool costs) worin bedeuten: in €/min KWT Tool costs per tool life in € Choosing the right type of cutting-tool KWT Werkzeugkosten je Standzeit in K Purchase price of tool in € material is almost impossible with- K AnschaffungskostenWa des Werkzeugs in Wa out considerations of this kind. For nT Anzahl der Standzeiten (bei Wendeplatten Anzahl der Schneidkanten) nT Number of tool lives per tool instance, a tool with a high purchase KWw Kosten für das Wechseln(for des solid verschlissenen shank tools or Werkzeugsprice in may be able to significantly KWs Kosten für das Nachschleifenbrazed des inserts: Werkzeugs nT = number (entfällt of reducebei Wendeplatten) unit fabrication costsin either be- regrinds; for indexable cutting cause it can produce a larger number Die Gleichung (22) zeigt, dass die Anschaffungskosten KWa in der Regel nur einen relativ inserts; nT = number of cutting of parts during its service life (higher kleinen Anteil der Werkzeugkostenedges je per Standzeit insert) KWT ausmachen.value ofDie nWT )beiden or because anderen it enables Sum- the manden sind meist größer. 34 | DKI Monograph i.18

Die Werkzeugkosten je Werkstück KW folgen dann der Gleichung

KWT KW = (23) nWT wobei bedeuten: KW Werkzeugkosten je Werkstück in nWT Standmenge, d. h. Anzahl der pro Standzeit bearbeiteten Werkstücke

Die vom Schneidstoff abhängigen Bearbeitungskosten je Werkstück K1 sind dann

K1 = th1 R + Kfix + KW = Kth1 + Kfix + KW (24) 6 Cutting-tool geometry

6.1 Rake and clearance angles machine operator and can disrupt the radius roughly in the range 0.3–0.5 Due to the large variation in the machining process. When performing mm. The width of the chip breaking machinability of copper alloys, the continuous turning operations on element is determined primarily by geometry of the cutting tool has to be these materials it is therefore fre- the thickness of the uncut chip h, adjusted to meet the specific character-Abb.quently 20: necessary Querschnitt to shape the chips einer whicheinggp iseschliffenen itself determined by theSp feedanleitstufe. istics of the work material being ma- into shorter coiled chips. This can be f and the tool cutting edge angle κr chined. Matching the tool geometry to achieved by using chip breakers that (h = f • sin κr), and to a lesser extent the workpiece material is particularly force the flowing chip into a specific by the width of the uncut chip b. A advisable if favourable chip formation form as soon as the chip has achieved wide chip requires a wide chip breaker. is to be achieved. Categorizing tool a minimum thickness of about 0.2–0.3 The following approximate guidelines geometry based on the main machin- mm. The tool geometry codes for tools are generally valid [23]: ability groups I–III is unsatisfactory, as that possess a chip breaker are indi- it represents too great a simplification. cated by an asterisk * in Table 12 (A*, In order to classify tool geometry, the B*, C*). The table also lists the angle of three main groups are further divided the chip breaker back wall. into three groups with the letter codes bf A, B and C (see Table 12). For cutting Chip breakers increase the extent of 50° or 70° tools with a more or less fixed cutting- chip compression, which induces edge geometry (e.g. milling cutters), higher machining forces and reduces hf the DIN 1836 standard distinguishes tool life. The tougher the chip material between the cutting teeth forms H, is or the greater the extent to which it N und W. Tooth shape H corresponds is deformed, the more pronounced this approximately to class A, tooth shape N effect becomes. to class B and tooth form W to class C. The degree of chip deformation The tool geometry designators assi- depends on the width of the chip gned to the copper-based materials breaking element and on the angle are listed in tables Table 9 to Table 11. between the effective rake face and Fig. 20: Cross-section through a chip breaking The machinability of a copper alloy the back wall of the chip breaker [23]: element ground into the tool can therefore be classified as in the the deeper the chip breaking ele- following example:Material CuZn39Pb3 ment and the steeper the back wall, = I.A.100 (I: main machinability group / the more the chip is compressed. As UndeformedSpanungsbreite b in mmWidth of chip alloy type, A: tool geometry designator, a general rule, a chip breaker height chipBreite width der Spanleitstufen b breaker bf in bmmf 100: machinability rating). of 0.8 mm and an angle of 70° or 50° in mm in mm Quelle:between the back wall and the tool’s 0,4 0 ,4...... 1,5 1,5 5 • h 5 • h Copper and cooper alloys have a effective rake face are recommended. 1,6 1, ...6 ... 7 7 8 • h 8 • h © WZL/Fraunhofer IPT Seite 21 pronounced tendency to form long The fillet between the rake face of the 7,5 7 ,5...... 12 12 12 • h12 • h ductile chips. The resulting ribbon and cutting tool and the back wall of the tangled chips can be hazardous to the chip breaking element should have a The chip breaker can also be aligned parallel to the tool’s cutting edge or aligned so that it widens or narrows Tool geometry Carbide HSS Angle of back wall towards the tool’s nose. designator of chip breaker1) γ α γ α Chip breakers that run parallel to the (°) (°) (°) (°) (°) cutting edge (alignment angle = 0°) do A not tend to direct chip flow toward or 0 - 8 6 5 - 10 8 50 A* away from the workpiece and there- B fore favour the formation of watch- 8 - 12 6 10 - 14 8 70 spring-like spiral chips. If the width B* of the chip breaker decreases towards C the nose of the tool (alignment angle 20 6 25 8 50 -70 > 0°), chip flow is directed away from C* the workpiece, favouring the creation 1 ) An asterisk * after the tool geometry designator indicates a tool with chip breaker. of cylindrical chips. Note: The chip breaker data applies only to turning tools or indexable inserts for turning or drilling; they do not apply to milling cutters, drill tools, etc. If the chip breaker is designed to wid- en towards the tool’s nose (alignment angle < 0°), the direction of chip flow Table 12: Tool geometry classification scheme is toward the workpiece surface, which

DKI Monograph i.18 | 35 Abb. 21: Spppanleitwinkel der Spanleitstufe

The effectiveness of a chip breaker is generally dependent on the ductility Chip breaker of the flowing chip, which itself is de- Spanleitwinkelalignment angle pendent on the properties of the work material and on the dimensions of the cut chip: the thinner the chip is, the harder it is to deform or break.

If some aspect of the machining operation, such as the roughness of the work surface or the weakness of the workpiece or tool, forces a thin chip to be produced, then chip form and flow cannot be controlled with any certainty. In such cases, machining ductile copper-based materials will almost inevitably lead to the formation of tangled chips. In order to limit the operational disruption caused by this type of chip, this stage of the machining process has to be carried out using a small depth of cut, as this lowers the strength of the cut chip by reducing its width. Fig. 21: Alignment angle of chip breaker Notwithstanding the above remarks, a chip breaker is unnecessary in situa- favours the formation of short chip tions in which it would be either useless curls, provided that the chip is not too (thickness of uncut chip is small) or ductile. There is, however, the risk that superfluous because the machining the chip can damage the newly machin- operation involves interrupted cut- Quelle: ed work surface. ting (as in, for example, milling), or because the chip is forced to flow in © WZL/Fraunhofer IPT a specific direction dictated by the Seite 22 geometry of the cutting operation (as in drilling or tapping).

36 | DKI Monograph i.18 7 Cutting fluids

Some copper-based materials are ma- with HSS. In contrast, carbide tools can In cases in which normal cooling- chined dry whereas others are machined maintain their hardness up to higher lubrication by a stream of cutting fluid while applying a cutting fluid. On some temperatures. (‘flooding’) is not applicable, the fluid machine tools, the use of a cutting fluid can be applied as a high-speed mist. is essential as the cutting fluid also If, on the other hand, the tool has sev- serves to lubricate parts of the machine. eral regions that are in direct contact In mist application, the cutting fluid with the workpiece but that do not con- is carried in a pressurized air stream During machining, the cutting fluid tribute to the material removal process and deposited in the cutting zone. The does not normally penetrate to the root (as is the case with reamers and taps), expansion of the air stream is accom- of the chip so that there is no direct then the cutting fluid is more important panied by a temperature drop that also influence of the tool’s cutting edge at as a lubricant than as a coolant. aids cooling (e.g. when tapping threads the tool-work contact zone. However, using cutting oil on multistation ma- the cutting fluid can have an indirect If the machine tool manufacturer does chines, which are normally operated effect on processes at the contact zone not specify the cutting fluid to be used, with emulsified oils). as cooling the workpiece and the tool emulsified oils are generally preferred increases the temperature gradient that when cooling is the predominant aim. Besides conventional flood-cooling, transports heat away from the work-tool copper-based materials can also be interface. Additionally, the cutting fluid The favourable cooling properties of subjected to neardry machining, in can quench the upper side of the chip these oil-in-water emulsions are due to which a minimum quantity lubrication and therefore facilitate the curvature the high specific heat capacity of water. (MQL) system is used, or dry machining and/or fracturing of the chip. Finally, If, though, lubrication is the primary in which no cutting fluid is used [25]. the cutting fluid also flushes clean the concern, cutting oils are preferred to Both approaches are technologically machining area. emulsions. Low viscosity oils are fa- feasible for machining copper alloys. voured as they are easier to deliver Whether a cutting fluid functions more and remove from the cutting zone. Which cutting fluid is used in practice as a coolant or as a lubricant depends depends not only technological feasi- on the machining operation being Cutting oils with added sulphur can bility, but frequently also on factors performed and the cutting tool used. As show a propensity to react with copper. determined by the machine tool set-up, HSS tools only retain their hardness up Therefore, either a sulphur-free cutting such as chip removal, heat dissipation, to the tempering temperature of around oil should be used or the workpiece lubrication of machine parts, and the 550–600 °C, cutting fluids are used should be rinsed immediately after possibility of influencing chip breakage. primarily as coolants when machining machining [24].

DKI Monograph i.18 | 37 8 Angaben zur Berechnung der Bearbeitungskosten 59

8 Angaben zur Berechnung der Bearbeitungskosten

Die Schnittparameter können rechnerisch optimiert werden, sofern nur ein Faktor betrachtet wird [WITT52]. Wenn aber, wie in der Praxis häufig, mehrere Schnittparameter wählbar sind, ist eine rein mathematische Optimierung praktisch nicht möglich.

Die Schnittparameterbestimmung und -optimierung kann mit Hilfe eines sukzessiven Vorge- hens vorgenommen werden [WITT52]: Hierzu werden zuerst die unabänderlichen Einfluss-

größen ermittelt. Dies können z.B. die Schnitttiefe ap, die als vorgegebenes Aufmass vorliegt,

aber auch die Schnittgeschwindigkeit vc, welche aus dem Drehzahlbereich und dem Bearbei- tungsdurchmesser resultiert, sein. Ein anderes Beispiel ist die Schneidenanzahl eines vor- handenen Fräsers. Diese fest vorgegebenen Größen werden ohne weitere Betrachtung übernommen. 8 Calculating machining costs Die nicht fest vorgegebenen Parameter werden im nächsten Schritt nach steigender Größe ihrer Exponenten in der erweiterten Taylor-Gleichung (8) geordnet. Meist ergibt sich hierbei

die Reihenfolge Schnitttiefe ap, Vorschub f (bzw. Spanungsdicke h) und Schnittgeschwindig-

keit vc. Da der Exponent von vc, verglichen mit den Exponenten von a und f, größer ist, fol-

gen für ap und f rechnerisch so große Werte, dass sie innerhalb der vorgegebenen Grenzen zu optimieren sind. Dieses gilt auch für den zulässigen Verschleiß am Standzeitende, der Cutting parameters can be optimized ofgrößte increasing zulässige size of their Wert exponents stellt hier in denThe kostengünstigsten optimization of the cutting dar. pa- using purely computational methods the expanded Taylor tool life equation rameters has thus been reduced to provided that only one parameter is (Eq. 8). determining the cutting speed vc as optimized at any time [26]. However, Als letzte Einflussgröße verbleibt diea function Schnittgeschwindigkeit of the specified tool life vc ,T. da ihr Exponent am größten if, as is often the case in practice, sev- Generally speaking, the relationship (8) eral cutting parameters can be varied ist. In der Mehrzahl der zerspanendenbetween Bearbeitungsaufgaben cutting speed and tool life folgt die Standzeit T der einfa- simultaneously, a purely mathemati- chen Taylor-Gleichung can be expressed using the simple cally based optimization is not usually Taylor equation (Eq. 6): possible. This usually results in the following k sequence of parameters: depth of cut = vCT cv (6) (6) Typically, the cutting parameters are ap; feed f (or thickness of the uncut determined and optimized by adopt- chip h); and cutting speed vc. In the range of cutting speeds typically ing a stepwise approach [26] that used, the achievable tool life T de- Im normalen Schnittgeschwindigkeitsbereich bewirkt jede Änderung von vc eine Änderung begins by identifying those parameters The depth of cut ap should initially be creases with increasing cutting speed vc von T: Wird vc erhöht, so sinkt T und umgekehrt. Gleichzeitig reduziert ein höheres vc die that can be regarded as fixed. Which chosen to be as large as possible, pro- and vice versa. A higher value of vc parameters these are depends on the vided,spanende of course, Bearbeitungszeit that it was not iden- th und willdamit also deren reduce Kostenthe machining je Werkstück, time th erhöht aber durch eine particular machining operation used. It tified as a fixed parameter (resulting, thus lowering the machining time costs could be the depth of cut ap, which is forkürzere example, Standzeit from a specified T die Werkzeugkostenstock al- per workpiece, je Werkstück but as it alsoKW .reduces limited by the specified stock allow- lowance) in the first stage of the opti- the tool life T, it causes an increase ance, or, as is frequently the case, mizationDa die process.beiden FurtherEinflüsse adjustments gegenläufig in the sind, tool hatcost dieper workpieceSumme KderW. As beiden Kostenarten je Werk- the cutting speed vc, which is limited to ap are then made in order to take these two costs evolve in opposite by the rotational speed range of the accountstück beiof the einer constraints bestimmten set by the Schnittgeschwindigkeit directions, their sum vperc,oK workpiece ein Minimum. Jedes Abweichen von machine tool and the diameter of the tool, work material and the machine passes through a minimum at a certain der kostenoptimalen Schnittgeschwindigkeit vc,oK erhöht die Zerspanungskosten je Werk- part being machined. A further ex- tool. Selecting the largest possible cutting speed voK. Fig. 22 shows how ample of such a fixed parameter is the depthstück, of da cut entwederreduces the dienumber spanende of Bearbeitungszeitthe various cost components oder aber vary die as a Werkzeugkosten steigen. In

number of teeth on the milling cutter cutsAbb. required. 22 ist Havingdie kostenoptimale determined the Schnittgeschwindigkeitfunction of cutting speed andvc,oK identi- dargestellt, welche aus der Auf- selected for use. These fixed value initial value of the depth of cut ap, the fies the location of the cost-optimized tragung der Kosten folgt. Dieser Wert wird über die zugehörige Standzeit ToK aus den Glei- parameters are then adopted as such feed f should then also be selected to cutting speed voK. Any deviation from in the calculation. bechungen as large as(23) possible. und (6) Here, errechnet: too, the this cost-optimized cutting speed voK value selected will be limited by factors will increase the unit cost of produc- Those parameters that are not prede- relating to the tool, work material and tion as either the machining time or Abb.termined 22: are Kosten then arranged in Abhän in orderggg igkeitmachine der used. Schnittgeschwindig keitthe tool( nach costs VDIwill rise. 3321 ) F K

n e t s o

k FertigungskostenTotal cost per piece s Tool costs g Werkzeugkosten n F u g rti e F KF,min Cost per piece K piece per Cost HauptzeitkostenMachining time costs

FixkostenNon-productive (fixed) costs

vc,ok Cutting speed V Sch nitt gesch wi ndi gk eit vc c

Fig. 22: Cost components plotted as a function of cutting speed (VDI 3321) © WZL/Fraunhofer IPT Seite 23

38 | DKI Monograph i.18 The cost-optimized tool life Tok can be Equation 25 shows how the cost- As a general rule, expensive tools derived with the aid of equations 6 optimized tool life ToK depends on should be used in combination with and 24. Differentiation and rearrange- the exponent -k, the tool costs per low values of the cutting parameters 8 Angaben zur Berechnung mentder Bearbeitungskosten yields Eq. 25: tool life KWT, the cost rate for operator 60 and on machine tools that are eco- and machine (including labour and nomical to run. On the other hand, machining overheads) KML and the tool low-cost tools can be used in combi- change time tw. The magnitude of the nation with the maximum technically K)1k( WT (25) ToK = (25) exponent -k depends on the work realizable cutting parameters and on R material/tool material pair and from machine tools that are more expensive where: the machining operation in use. to run. worin bedeuten ToK = C ost-optimized tool life in The exponent -k is large for HSS tools Similar calculations can be carried out min and/or work materials that are difficult to determine the time-optimized cut- ToK = kostenoptimale Standzeit in min to machine, but smaller for cemented ting speed vot, i.e. the cutting speed –k = entsprechend Gleichungk = Gr adient(5) of straight line in carbide tools and/or work materials that minimizes machining time per tool-life plot workpiece [26]. This will not be dis- K = Werkzeugkosten je Standzeit nach Gleichung (22) thatin are easy to machine. It there- WT fore follows that, all other machining cussed further here as there is gener- R = Restkostensatz,K WTd.h. = Kostensatz Tool costs per des tool lifeArbeitsplatzes in € as conditions ohne Werkzeugkostenbeing equal, a material in that ally no significant difference between /min defined in Eq. 22 is difficult to machine will require a voK and vot. larger value of the cost-optimized tool KML = Cost rate for operator and ma- life ToK. It is, however, not always If a number of (possibly different) Aus der Gleichung 25 folgt, dass die kostenoptimale Standzeit ToK von dem Exponenten –k, chine + labour and machining possible to meet this requirement in tools are being used simultaneously den Werkzeugkosten je Standzeit KWToverheads und dem in €/hRestkostensatz practice.R abhängig ist. Dabei ist –k to machine a part, Equation 25 has to von der Werkstoff/Schneidstoff-Paarung und dem Zerspanungsverfahren abhängig. Aus den be modified as KWT now represents the tw = Tool change time If the calculated value of ToK, and thus sum of the tool costs for each of the Werkzeugkosten je Standzeit KWT folgt, dass teure Werkzeuge aufvoK , kostengünstigenlies outside the tool lifeMaschi- range cutting tools being used simultaneous- nen schonende eingesetzt werden sollten. Andererseits zeigt dertypically Restkostensatz used in practice, R, the dass optimum ly. The value calculated for the cost- value achievable under the given optimized tool life ToK will therefore be kostengünstige Werkzeuge auf kostenintensiven Maschinen vomoperating technologisch conditions is thatmaximal value greater than when a single tool is used einzusetzen sind. which comes closest to the ideal [27, 28]. calculated value.

Der Exponent –k ist bei HSS und/oder schwer zerspanbaren Werkstoffen groß, bei HM und/oder gut zerspanbaren Werkstoffen kleiner. Daraus folgt, dass ein schwer zerspanbarer

Werkstoff bei gleichen Verhältnissen eine größere Standzeit ToK verlangt. Dieser Forderung kann jedoch nicht immer entsprochen werden.

Liegt berechnete Wert für ToK und damit vc,oK außerhalb des in der Praxis verwendbaren Bereichs, so stellt die größte Annäherung an ihn das in der Praxis erreichbare Optimum dar.

Für die zeitgünstigste Schnittgeschwindigkeit vot existieren vergleichbare rechnerische Voge- hensweisen [WITT52]. Hierauf wird jedoch nicht näher eingegangen, da in der Regel kein wesentlicher Unterschied zwischen vc,oK und vot existiert.

Soweit in „simultan zerspanenden Werkzeugkollektiven“ mehrere, eventuell auch unter- schiedliche Werkzeuge gleichzeitig zerspanen, ändert sich die Gleichung (25), da für KWT nun die Summe der Werkzeugkosten der gleichzeitig zerspanenden Werkzeuge einzusetzen ist. Der Wert für ToK wird damit größer als beim separat zerspanenden Werkzeug [VOSS76, BURM81].

DKI Monograph i.18 | 39 9 Ultra-precision machining of copper

Copper finds widespread use in optical of the chemical affinity of iron for car- that at the centre of the workpiece the systems. Ultra-precision machining of bon [21, 29, 30]. cutting speed would be zero. Although copper can produce optical compon- the cutting forces exerted in ultra- ents with high-quality mirror surfaces The key features of ultra-precision precision machining are typically less and high dimensional accuracy. In this machine tools are the aerostatic or than 1 N, machines of high rigidity are chapter we briefly explain the basic hydrostatic guide systems, air spindles required in order to avoid vibrations principles of ultraprecision machining and linear direct drives. To achieve and to achieve the required dimen- and some of its applications, followed a high level of thermal stability and sional precision of less than 0.1 µm. by an examination of the quality good damping characteristics, granite levels achievable and the technical is the preferred material for the base of The spindle speed chosen will depend constraints of the technique. the ultra-precision machine. on the diameter of the component being machined, the work material The two main ultra-precision machin- and the dynamics of the additional 9.1 Principles of ultra-precision ing techniques used with diamond axes. Spindle speeds of up to 2500 rpm machining cutting tools are turning and fly cut- are typically used in the production of Ultra-precision machining (also com- ting. Turning enables a broad variety of metal optics by ultra-precision ma- monly known as diamond turning) geometries to be machined, and fast chining. As in macro-scale machining, differs from conventional machining tool servo (FTS) systems now allow the the feed is determined by the tool techniques in the cutting material fabrication of non-rotationally sym- nose radius and the specified surface used. Monocrystalline diamond metric optical surfaces. Fly cutting can roughness. The depth of cut depends enables tools to be fashioned with very be thought of milling with a single- on the work material. For non-ferrous precise cutting edge geometry and low tooth milling cutter. The fly cutter metals, recommended depths of cut wear. The nose radii of such tools are typically has a single-point diamond for turning operations are 20–50 µm typically around 50 nm. When com- cutting tool mounted on the periphery for roughing and about 3 µm for finish bined with ultra-precision machining of a rotating disc. Fly cutting is used to machining. technology, diamond cutting tools can produce flat surfaces or to create linear be used to fabricate optical surfaces grooves. The geometry of the groove or Ultra-precision machining lathes are with a surface roughness (Ra) of only a slot is determined by the shape of the generally equipped with a minimum few nanometres (see Fig. 23). cutting tool (radius, facetted, v-form). quantity lubrication system. Isoparaf- fins are transported to the cutting zone One advantage of copper alloys and The quality of a surface produced by in a pressurized air stream where they other non-ferrous metals is that they diamond cutting is slightly depen- are atomized. In addition to lubricat- are very easy to machine with mono- dent on the cutting speed. Generally ing, the MQL system also ensures that crystalline diamond tools. Steel cannot speaking, turning operations are per- the chips are flushed from the cutting be machined with these tools because formed at a constant spindle speed so zone. The lubricants have a high heat of vaporization and do not therefore influence the cutting process by evapo- rative cooling [29].

9.2 Example applications involving copper alloys Copper and copper alloys are used for different ultra-precision machining applications. Copper is widely used for fabricating optical components for laser systems. Copper is chosen not only because it permits fabrication of high-quality surfaces, but also, and importantly, because of its high heat capacity. Despite the high-quality surface finish and additional surface coatings, the mirror material can heat up thus deforming the shape of the mirror. To avoid such impermissible variations in form, the mirrors are cooled by means of internal cooling channels. In order to produce the Fig. 23: Ultra-precision machining of a structured plane brass surface best possible mirror surfaces, the

40 | DKI Monograph i.18 copper that undergoes diamond turn- quality of the surface finish that can individual grains in the microstruc- ing should have the highest possible be achieved and the cutting forces ture therefore respond differently purity. The copper grade of choice is that arise [29, 31]. The characteristics and this leads to the variation in so-called OFHC (oxygen-free high- of the machined surface are strongly levels described above. conductivity) copper. The mirrors dependent on the material’s grain produced are used not only to guide structure and grain boundaries. The effects of grain structure are also and focus the light beams, but also to As a result of the so-called spring- apparent in the microstructuring of shape the beams as well. By deploying FTS systems, non-rotationally symmetric surface structures can be created on the mirror surface. For example, multifaceted mirror surfaces can be created that act as beam homogenizers. In addition, the focus of the beam can be modified by using free-formed mirrors.

Besides being used for mirror optics, copper and copper alloys are also used to make the moulds for the in- jection moulding of polymeric optical components. Because of their greater hardness, copper-beryllium alloys are also used in such applications. However, according to the Restriction of Hazardous Substances Directive 2002/95/EC (RoHS), beryllium-containing components are subject to labelling requirements. Brass is used not only as a mould insert for the in- jection moulding of plastics, but also Fig. 24: Diamond cut surface of OFHC copper [29] for the fabrication of micro-structured masters. Brass plate is the starting material for these structural masters, back effect (compression of individ- the substrate surface, particularly which can be up to one square metre ual grains during the machining the formation of burrs along grooved in size. Replication masters of this process), diamond cutting of a plane structures. Figure 25 depicts V-shaped kind are used, for example, in display surface of OFHC copper can yield level grooves with a depth of 7 µm applications where the grooved or differences of up to 40 nm between that have been produced by plunge- pyramidal structures are machined by neighbouring crystals (see Fig. 24) cut turning in the surface of a piece fly cutting. [29]. of OFHC copper. The burr formation along the edges of the grooves varies The formation of these surface struc- with the grain structure of the copper, 9.3 Material properties and tures is a result of the anisotropic which has been made visible here by their influence on ultra-precision behaviour of the work material. Due etching. machining to the face-centred cubic (fcc) lattice The results of an ultra-precision structure of copper, the packing As the material properties change in machining operation depend not densities within the individual lattice the vicinity of the grain boundaries, only on the cutting tool and the planes differ, which results in elastic machining conditions and therefore machine characteristics, but also on and plastic material properties that burr formation change accordingly. the properties of the work material. are strongly directionally dependent. In the material shown here, the grain The copper and copper alloys used For example, the modulus of elasticity size is in the range 50–80 µm. The in engineering applications usually of a copper single crystal varies be- homogeneity of the microstructure have a polycrystalline microstructu- tween 68 and 190 kN/mm² depending can be improved by reducing the re. This has to be taken into account on the load direction. In polycrystal- grain size. Microcrystalline copper when the required precision in- line microstructures, these effects materials can be produced by severe creases or when the dimensions of reinforce each other due to the differ- plastic deformation (SPD). One such surface features decrease. A number ent orientations of the grains in the SPD technique is the ECAP method of studies have been carried out on microstructure. When a polycrystalline (Equal Channel Angular Pressing) with polycrystalline copper to examine the copper substrate is machined the which a high degree of deformation

DKI Monograph i.18 | 41 Abb. 25: Gratbildung in Abhän gggigkeit der Kornstruktur [[]BREC09]

burr-free groove edge

burred groove edge

Fig. 25: Grain-structure-dependent burr formation [32]

can be achieved thus generating se- microstructuring tests [32]. Neverthe- vere dislocations within the material. less, diamond cutting of OFHC copper Samples of material produced by ECAP can produce surfaces with a roughness Quelle: have already been successfully used in parameter Ra down to 3 nm [29].

42 | DKI Monograph i.18 10 Recommended machining parameters for copper and copper alloys

The tables of recommended machin- In the following sections we discuss the cutting speed vc of about 10 % is ing parameters list suggested cutting and explain the recommended ma- recommended. speeds for machining operations such chining parameters for a variety of as turning and milling as a function machining operations. When turning is performed on a cast of the undeformed chip thickness. The part with a normal sand-textured skin, following procedure can be used to the cutting speed should be reduced by identify the correct machining para- 10.1 Turning of copper and copper about 15 % when carbide cutting tools meters: alloys are used and by about 20 % for HSS The values quoted in Table 13 are tools. If the material to be machined is stan- estimated to be valid in about 70 % of dardized, locate the material in Tables cases. They are based on a flank wear When machining copper materials with Table 9 to Table 11 and note down its land width of VB ≈ 0.6 mm at the end a strain hardened skin, the machin- machinability rating and the tool geo- of the tool’s life, and a tool life of ability of the material is determined by metry designator. If the material has T = 30–60 min for carbide cutting tools the machinability of the skin, which is not been standardized, select the most in group N10 (N20), or T = 45–90 min itself dependent on the hardness of the similar alternative material based on for HSS cutting tools (HS10-4-3-10). skin layer. the main alloying components. If the tool life T is to be doubled, the For turning operations in which chip Use the material’s machinability rat- value of vc should be reduced by about flow is restricted, such as form turning, ing to determine the recommended 16 % for carbide tools and by about groove cutting, parting off and thread- machining parameters in Table 13 to 10 % for HSS tools. However, in the ing, the cutting speed vc should be Table 19 for the machining operation of case of ductile, high copper content lowered by about 40 % when carbide interest. materials, doubling the tool life T of a tools are used and by about 50 % when carbide tool requires a reduction in the HSS turning tools are deployed. Use the tool geometry designator to cutting speed vc of around 30 %. determine the recommended tool geo- If an HSS grade other than HS10-4-3-10 metry from Table 12. If the tool life is defined as the cutting is used, the following correction factors time to reach a flank wear land width of apply: As machinability depends on the VB ≈ 0.4 mm, then to achieve the same HSS Faktor for vc strength and hardness of the work tool life T as that based on a value of VB HS10-1-4-5 0,82 material, tensile strength and Brinell ≈ 0.6 mm, the cutting speed vc would HS12-1-4 0,76 hardness data are included in Table 9 need to be reduced by about 35 % for HS6-5-2 0,72 to Table 11. If the material strength or carbide tools and by about 15 % for HSS HS2-9-1 0,65 hardness differs from the values given, tools. the recommended machining parame- It is not uncommon that the recommend- ter determined by the machinability Uninterrupted cutting has practically no ed cutting speeds in Table 13 cannot be index will need to be interpolated or effect on the service life of HSS tools; if attained in practice due to constraints extrapolated accordingly. carbide tools are used, a reduction in such as limits to the maximum achiev-

Undeformed chip thickness h [mm]

]Machinability Carbides HSS rating 0,1 0,32 0,8 0,1 0,32 0,63

100 1260 1000 800 154 85 60

90 1150 910 730 142 79 57

80 1030 800 660 130 74 53

70 910 730 580 117 68 50

60 800 630 510 105 62 46

50 680 540 430 93 57 43

40 570 440 360 81 51 39

30 450 360 284 68 46 36

20 220 160 120 36 28 22

Table 13: Recommended machining parameters for turning copper and copper alloys Recommended cutting speeds vc in m/min as a function of the undeformed chip thickness h in mm and the machinability rating

DKI Monograph i.18 | 43 Solid carbide HSS Carbide inserts D = 3 - 20 [mm] Machinability rating

vc [m/min] vc [m/min] vc [m/min]

100 80 250 400

90 74 239 373

80 69 228 345

70 63 216 318

60 58 205 290

50 52 194 263

40 46 183 235

30 41 171 208

20 35 160 180

Table 14: Machining parameters for drilling copper and copper alloys Recommended cutting speeds vc in m/min for HSS, solid carbide and index-able-insert drills as a function of the machinability rating

Diameter D [mm]

3 - 5 5 - 8 8 - 12 12 - 16 16 -20

HSS 0,1 - 0,16 0,16 - 0,25 0,25 - 0,32 0,32 - 0,4 0,4 - 0,5 Feed f [mm] Carbide 0,08 - 0,12 0,12 - 0,18 0,18 - 0,23 0,24 - 029 0,3 - 0,35

Table 15: Feeds for drilling copper and copper alloys Recommended feed as a function of drill diameter able spindle speed or when a workpiece Because the properties of copper- than about 18 mm (and lengths up to with a very small diameter is being based materials span such a broad about 2.5 • d). Type N and type H drills machined. In such cases, the machining range, the choice of drill type and/or can be used if the machine is suffi- parameters have to be adjusted to take cutting-edge geometry depends on the ciently rigid and sufficiently powerful. account of the particular machining type of material to be drilled: Copper Whether these drill types can be used operation and the prevailing cutting alloys that yield short, fragmented to drill copper-based materials that conditions. chips are drilled using type H drills (cf. produce long continuous tough chips DIN 1414, sheet 1 and 2), type N drills depends on the availability of index- are chosen for materials producing able inserts with chip breaker grooves. 10.2 Drilling and counterboring of longer curled chips, while type W drills copper and copper alloys are used for those materials that yield Drills with internal cooling holes are Copper-based materials are generally extremely long continuous chip forms. recommended for drilling deep holes. drilled using HSS twist drills. These The removal of long tough chips is The cutting fluid flows through the are supplemented by solid carbide easier in type W HSS drills that have coolant hole and can therefore be de- drills, indexable-insert drills and polished or chromeplated flutes. livered more easily to the drill’s cutting (deep-hole) gun drills. Recommended edges as well as helping to flush the cutting speeds for HSS, solid carbide Type H drills correspond to a class A chips away from the cutting zone. and indexable-insert drills are listed in cutting-edge geometry, type N drills Table 14. to class B, and type W drills to class C Gun drills are used to drill extremely (Table 12). deep holes (L > 10 • d) whenever high The feed rate to be used during a dril- demands are placed on the dimen- ling operation depends on the work/ Commercially available carbide drills sional tolerances, alignment and tool material pairing, but primarily include drills with brazed carbide surface quality of the bore hole wall. on the drill diameter. The required tips, solid carbide drills or drills with feed per revolution increases with in- indexable carbide inserts. Other rules apply when drilling with creasing drill diameter. Recommended gun drills but will not be discussed feed values are listed in Table 15 as a Carbide indexable insert drills prove further here. Suffice to say that the function of drill diameter and the tool to be the most economical tools when geometry of the tool’s cutting-edge material. drilling holes with diameters greater and the feed rate depend primarily on

44 | DKI Monograph i.18 achieving a chip form that can be easi- walls of a drill guide bushing, and on cutting tool material with a longer tool ly removed from the cutting zone. how easily the cutting fluid is able to life can result in a significant reduc- reach the cutting tip. This is why when tion in the machining costs per hole. In drilling operations, the range of using a drill that does not have coolant achievable cutting speeds is deter- channels the choice of cutting speed In addition to the above criteria, the mined by the chip formation process. vc depends not only on the position of geometry of the hole to be produced Within this range, the cutting speed vc the drill during drilling (horizontal or must also be taken in to account is selected primarily on the basis of the vertical), but also on the depth of the when selecting vc and f. When drilling tool costs per tool life, KWT, that itself hole being drilled. through-holes, the outer corners of the depends on the type of drill used, drill tip are subject to increased wear its diameter and length. The cutting Finally, the choice of cutting speed during drill breakthrough. It is there- speed also depends on whether the is influenced by the work material. fore advisable to reduce the cutting margin of the drill rubs against the Despite higher initial purchase costs, a speed and the feed rate by about 5 %

HSS Hole diameter d [mm]

Machinability uncoated coated 5 10 16 25 40 63 rating

vc [m/min] f [mm]

100 14 19

90 13 18

80 13 17

70 12 16 0,15 0,2 0,25 0,4 0,4 60 11 15 - - - - - 0,6 0,2 0,3 0,35 0,5 0,5 50 10 14

40 10 13

30 9 12

20 8 11

Table 16: Recommended machining parameters for reaming copper and copper alloys with HSS reamers Recommended cutting speeds vc in m/min as a function of the machinability rating and recommended feeds f in mm as a function of the hole diameter

Carbide Hole diameter d [mm]

Machinability HC - N10 5 10 16 25 40 63 rating

vc [m/min] f [mm]

100 30

90 27

80 25

70 22 0,2 0,3 0,35 0,4 05 60 19 - - - - - 0,6 0,3 0,4 0,45 0,5 0,6 50 16

40 14

30 11

20 8

Table 17: Recommended machining parameters for reaming copper and copper alloys with solid carbide reamers Recommended cutting speeds vc in m/min as a function of the machinability rating and recommended feeds f in mm as a function of the hole diameter

DKI Monograph i.18 | 45 during exit; this restriction does not The specified reaming allowance should the hole can be improved by using a apply when drilling blind holes. not be too small and should be roughly tool in which the direction of the flute equal to the allowance typically assum- helix is opposite to that of the cut (e.g. For countersinks and core drills (as ed in countersinking. A tool cutting left-hand helix, right-hand cut) as detailed in DIN 343, 344, 222 and in edge angle κr of about 45° is generally this ensures that the chips are pushed DIN 8043, 8022), the machining data selected for short-chip alloys, while an ahead of the tool as it progresses into can be derived from the corresponding angle of approximately 30° is typical the hole. data for HSS drills: the cutting speed vc for long-chip materials. Smaller angles should be reduced by 30 %, while the tend to cause the reamer to seize, re- Cutting oils are recommended when feed f should be increased by 100 %. ducing tool life without improving the performing reaming operations. quality of the surface finish. It is important that the reamer runs sufficiently Tooling costs can be reduced if a reamer 10.3 Reaming copper and copper true at the start of the cut and that the with an indexable cutting insert can alloys transition from the lip to the margin is be used instead of a solid multiflute The service life of a reaming tool slightly curved. reamer for the reaming operation of depends more on the dimensional tol- interest. erances of the hole to be machined than The end of the tool life should not on the work material. Under favourable be determined by the dimensional conditions, the most cost-effective accuracy of the reamed hole, but rather 10.4 Tapping and thread milling tool life ToK can be achieved down to a by a flank wear land width of VB ≈ 0.3 copper and copper alloys tolerance grade of IT 8. If tolerances are mm at the lip. Failure to adopt this Selecting the right type of tap is crucial tighter, it is generally not possible to wear criterion will result in a significant if a tapping operation is to be suc- achieve the optimum tool life. reduction in the number of regrinds cessful. The choice of tap depends on The cost-optimized cutting speed voK for possible, thereby substantially increas- the work material and the geometry reaming operations is therefore signif- ing the tool costs per piece. of the required thread. Recommended icantly lower than the values that are cutting speeds are listed in Table 18. typically recommended. Recommended The roundness of a hole produced by a values for reaming operations are listed multiflute reaming tool tends to adopt Straight-flute taps are generally used in Table 16 and Table 17. a multi-cornered polygonal profile with for short-chip alloys and spiral-point one ‘corner’ more than the number of taps are usually chosen when tapping In contrast, quite high feeds f can be cutting edges on the tool. Choosing a through-holes as they tend to eject selected for reaming because the tool reamer with an odd number of cutting the chip ahead of the tool. This is not feed has only a relatively minor effect edges does not, however, eliminate possible when tapping blind holes, on the number of holes that can be this problem, though it can be reduced for which taps with bottoming style reamed per tool life, on the conformity significantly by using reamers with very chamfers are used. to prescribed tolerances and on the irregularly spaced flutes. When reaming surface roughness of the hole wall. ductile materials, or when reaming Straight-fluted, spiral-point taps with through-holes, the surface finish of a pitch of up to about 2 mm are also used to cut threads in through-holes or relatively deep holes in long-chip HSS materials. However, taps with a right- Carbide N10 uncoated coated hand helix are used to cut (right-hand) Machinability rating threads in blind holes. Helix angles of about 15°, 35° and 45° are readily avail- vc [m/min] able commercially. The greater the L/d 100 40 20 30 ratio and the tougher the chip formed, 90 39 19 29 the larger the helix angle should be.

80 38 19 28 Besides tapping, internal threads can also 70 36 18 26 be cut by thread-milling. Coated carbide 60 35 17 25 thread mills can cut threads in brass at cutting speeds of 200–400 m/min. If 50 34 17 24 uncoated tools are used, the cutting 40 33 16 23 speeds should be reduced by 25 %. The feed per tooth fz is typi- 30 32 15 22 cally in the range 0.05 to 0.15 mm. 20 30 15 20 The lower end of the range should be selected if machining long-chip Table 18 : Recommended cutting speeds for tapping copper and copper alloys brasses. Cutting speed and feed in

46 | DKI Monograph i.18 thread milling operations also depend If both types of milling operation We can distinguish two types of pe- on the diameter of the thread: the can be used for a particular job, face ripheral milling depending on the di- greater the thread diameter, the higher milling is generally more economical. rection of rotation of the milling cutter. the cutting speed and the larger the In face milling an uncut chip thickness In ‘up milling’ the direction of motion feed per tooth that can be selected. If of zero does not usually arise. Very thin of the cutter’s teeth when they engage unalloyed copper is being machined, chip thicknesses at the start of the cut with the work is opposite to the feed. the cutting speeds can be increased by can cause rubbing between the cutting In ‘down milling’ or ‘climb milling’ the about 25 % and the feeds doubled. edges and the workpiece surface, spoil- direction of motion of the teeth when ing surface quality and promoting tool they cut into the work is the same as wear. Furthermore, the minor cutting the feed direction. 10.5 Milling copper and copper edges dull more quickly than the major alloys cutting edges whose wear during face If the work material does not have In face milling, the machined surface milling is not of primary importance a hard, wear-inducing skin, down is produced by the cutting edges on in determining the roughness of the milling is normally preferred to up the end face. If the surface is produced milled surface. milling as down milling results in less by the cutting edges on the outside rubbing between the cutting teeth periphery of the cutter, the technique In contrast, peripheral milling has the and the work surface, and the cutting is known as peripheral milling. If advantage that it can produce geo- forces are more favourably distributed. the peripheral cutting edges are not metrically complex shapes in a single However, when copper and copper al- straight, but profiled, the so-called pass. However, in peripheral milling loys are being machined, the resulting form milling cutter generates a shaped the roughness of the machined sur- difference in tool life is not large. surface determined by the form of the face is directly determined by the state tool’s peripheral cutting edges. of the major cutting edges. The cutting materials typically used for milling copper-based materials are the

Face milling with indexable inserts

HM – N10 uncoated DP – N05 Machinability rating

hz in mm

0,1 0,2 0,1 0,2

100 580 540 1050 1000

90 554 516 1006 954

80 530 494 963 910

70 507 472 923 868

60 484 451 884 829

50 463 431 847 791

40 443 412 811 754

30 423 394 777 720

20 405 377 744 687

Table 19: Machining parameters for face milling of copper-based materials using in-dexable teeth Recommended cutting speeds vc in m/min as a function of the undeformed chip thickness hz in mm and the machinability rating

DKI Monograph i.18 | 47 Peripheral milling with an end milling cutter

Tool material fz in mm Machinability HSS solid carbide Diameter of mill cutter in mm rating uncoated coated uncoated coated 1 6 12 20 100 45 80 140 280 Roughing 90 41 73 120 230 80 38 67 110 210 0,004-0,006 0,01-0,02 0,04-0,5 0,05-0,07 70 35 61 100 200 60 32 56 96 190 Finishing 50 29 52 92 180 40 27 47 87 175 0,004-0,006 0,01-0,02 0,04-0,5 0,05-0,07 30 10 Richtwerte24 43für die zerspanende85 Bearbeitung165 von Kupfer und Kupferlegierungen 75 20 22 40 80 160 bis unteren Bereich zerspanen. Die Spanungsdicke ergibt sich beim Stirnfräsen aus Vor- Table 20: Machining parameters for peripheral milling of copper-based materials using end milling cutters schub je Schneide und Umdrehung fz und Einstellwinkeln nach Recommended cutting speeds vc in m/min and feeds per tooth fz in mm as a function of the diameter of the milling cutter and the machinability rating 6,114 ° a carbide application groups N10 and e a = Working engagement Inh mperipheral= milling,z sinf the() chip is curled e (25) N20, and the HSS grades HS6-5-2, HS6- somewhat slike° a comma withD one of (radial depth of cut) 5-2-5, HS2-9-1-8 and HS12-1-4-5. its ends having, in theory at least, zero D = Diameter of milling cutter In milling operations, the undeformed thickness. The average thickness of chip thickness perBeim tooth Umfangfräsen and per wirdthe undeformedein kommaförmiger chip is given Span by the abgehoben, As milling der cutters an einemvary significantly Ende theore- in revolution hm is typicallytisch die in Dickethe range Null hat.following Als Spanungsdicke equation: gilt hierbei ein mittlererterms of the Wert number nach of dercutting Gleichung teeth 0.1–0.35 mm. Face milling cutters and they have and the associated tool costs, heavy cutting tools tend to be at the the recommended cutting speeds vc can upper end of this range, while periph- 6,114 ° a provide only broad guidance. The values h = f e (26) (26) eral and weaker tools are located in m ° z D listed in Table 19 refer to face milling 10 Richtwerte für die thezerspanende middle to lower Bearbeitung region. The unde- von Kupfer unds Kupferlegierungen 75operations using indexable inserted formed chip thickness in a face milling where: tooth cutters made from uncoated bis unteren Bereich zerspanen.operation is determinedDieDabei Spanungsdicke bedeuten by the feed ergibthm sich= Undef beimormed Stirnfräsen chip thickness aus per Vor- carbide or polycrystalline diamond. per tooth and revolution fz and the tooth and revolution schub je Schneide undcutting Umdrehung edge angle fz und κ as Einstellwinkelnfollows: f znach = Feed per tooth and revolution If the cutting speed vc is reduced by hz = Spanungsdickeκ r = Tool je cutting Schneide edge angleund Umdrehungabout 10 %, the tool life can be ϕ s = Angle of cutter engagement effectively doubled; if the cutting 6,114 ° fz = a e Vorschub je Schneide und Umdrehung h = sinf () (25) hm = Average(25) thickness of undeformed speed is increased by 10 %, the tool Abb. 26:Umfanm gsfräsen imz Gleich- und Gegenlauf s ° r = D Einstellwinkelchip life will be halved. ap = Depth of cut (feed) s = Fräserschnittwinkel If milling a material with a typical sand- Beim Umfangfräsen wird ein kommaförmigerhm = Span mittlere abgehoben, Spanungsdicke der an einem Ende theore- cast skin, the cutting speed of a carbide milling cutter should be reduced by tisch die Dicke Null hat. Als Spanungsdickeap = gilt hierbei Schnitttiefe ein mittlerer (Zustellung) Wert nach der Gleichung about 15 %, that of a HSS tool should be ae = Eingriffsgröße lowered by around 20 %. 6,114 ° D a = Fräserdurchmesser h = f e (26) m ° z D The recommended speeds are based on s a flank wear land width of VB ≈ 0.6 mm n n at the end of the tool’s life (rough milling). If the tool life is defined to be the Dabei bedeuten machining time to reach a flank wear Da Fräser hinsichtlicha Schneidenzahl und Werkzeugkostena in einen großen Bereich variie- e e land width of VB ≈ 0.4 mm, then to vf vf Vorschub fz ren, können Empfehlungenfz zur Wahl der Schnittgeschwindigkeitachieve the vsamec nur tool bedingt life as that gegeben based hz = Spanungsdicke je Schneide und Umdrehung fz werden. Die Richtwerte in Tab. 19beziehen auf das Strinfräsenon VB ≈ 0.6 mm,mit theMesserköpfen. tabulated values Als fz = Vorschub je SchneideDownGlei chl und aumillingff rä senUmdrehung GUpegen millingl auff rä sen would need to be reduced by about 50 % Schneidstoffs sind hier unbeschichtetes Hartmetall und Diamant aufgeführt. r = Einstellwinkel for carbide tools and by about 30 % for Fig. 26: The ‘down’ and ‘up’ forms of peripheral milling HSS tools. s = Fräserschnittwinkel Um die Standzeit T zu verdoppeln, ist der Wert vc um etwa 10 % zu senken, um sie zu hal- hm = mittlere 48Spanungsdicke | DKI Monograph i.18 © WZL/Fraunhofer IPT bieren um etwa 10 % zu erhöhen. Seite 27 ap = Schnitttiefe (Zustellung) ae = Eingriffsgröße Bei einer normalen Sandgusshaut sind die vc-Werte bei HM um etwa 15 %, bei HSS um D = Fräserdurchmesser etwa 20 % zu reduzieren.

Die Richtwerte gelten für eine Verschleißmarkenbreite VB 0,6 mm am Standzeitende

(Schruppfräsen). Für VB 0,4 mm bei gleicher Standzeit sind die Tabellenwerte bei HM um Da Fräser hinsichtlich Schneidenzahl und Werkzeugkosten in einen großen Bereich variie- etwa 50 %, bei HSS um 30 % zu senken. ren, können Empfehlungen zur Wahl der Schnittgeschwindigkeit vc nur bedingt gegeben werden. Die Richtwerte in Tab. 19beziehen auf das Strinfräsen mit Messerköpfen. Als Schneidstoffs sind hier unbeschichtetes Hartmetall und Diamant aufgeführt.

Um die Standzeit T zu verdoppeln, ist der Wert vc um etwa 10 % zu senken, um sie zu hal- bieren um etwa 10 % zu erhöhen.

Bei einer normalen Sandgusshaut sind die vc-Werte bei HM um etwa 15 %, bei HSS um etwa 20 % zu reduzieren.

Die Richtwerte gelten für eine Verschleißmarkenbreite VB 0,6 mm am Standzeitende

(Schruppfräsen). Für VB 0,4 mm bei gleicher Standzeit sind die Tabellenwerte bei HM um etwa 50 %, bei HSS um 30 % zu senken. 11 Appendix

11.1 Sample machining applications

Alloy group Material Machinability and Typical applications Machinability processability rating Designation Number Number (EN) (UNS)

Low-alloyed copper CuPb1P CW113C C18700 – – 85 (no P) alloys – non-age- CuSP CW114C C14700 Good machinabil- Screw-machine prod- 85 hardenable ity; free-cutting ucts, machine-turned copper parts; screws; nuts; nozzles for welding and cutting torches; valve seats for fittings CuTeP CW118C C14500 Good machinabil- Nozzles for welding 85 ity; free-cutting and cutting torches; copper screws Copper-nickel-zinc alloys CuNi7Zn39Pb3Mn2 CW400J – – – – CuNi10Zn42Pb2 CW402J C79800 – – – CuNi12Zn30Pb1 CW406J C79300 – – – CuNi18Zn19Pb1 CW408J C76300 – – – Copper-tin-zinc alloys CuSn3Pb7Zn9 C84400 – – 90 CuSn4Zn4Pb4 CW456K C54400 – General plain bearings; 80 electrical connectors; contacts; toggle lever bearings Leaded binary copper-zinc CuZn35Pb2 CW601N C34200 – – 90 alloys CuZn36Pb2As CW602N C35330 – Sanitary fittings (85) CuZn36Pb3 CW603N C35600 Good machinability Screw-machine prod- 100 and cold workable; ucts, machine-turned main alloy in USA parts; pins; precision for use on screw machined parts for machines and clocks, watches and machining centres optical applications CuZn37Pb0,5 CW604N C33500 – – 60 CuZn39Pb0,5 CW610N C36500 – Contact pins 60

Wrought copper alloys alloys copper Wrought CuZn38Pb1 CW607N C37000 – – 70 CuZn38Pb2 CW608N C37700 Good machinability Valve components, 80 (90) and cold workable optical and precision machined parts CuZn39Pb2 CW612N – Excellent machina- Watch and clock move- (85) bility and drilling/ ments; terminal strips; milling quality; electrical connectors good stamping/ punching quality CuZn39Pb3 CW614N C38500 Excellent machina- Form turned parts; 90 (100) bility; main alloy in precision machined Europe for use on parts; clock and watch screw machines and components; machining centres; electrical applications; form turned parts ball pen tips CuZn40Pb2 CW617N C37700 Excellent ma- Form turned parts of 80 (95) chinability; good all kinds; precision hot workability; machined parts; clock extruded sections and watch components CuZn43Pb2Al CW624N – – – – Multi-component copper- CuZn40Mn1Pb CW720R – – Roller bearing cages; – zinc alloys screw-machine products

CuZn21Si3P CW724R C69300 – Lead-free machining – alloy

Table 21 a: Machinability classification of standardized copper-based materials Machinability group I: Copper alloys with excellent machining properties

DKI Monograph i.18 | 49 Alloy group Material Machinability and Typical applications Machinability processability rating Designation Number Number (EN) (UNS)

Copper-zinc casting alloys CuZn33Pb2-C CC750S –– Gas and water valve – bodies CuZn39Pb1Al-C CC754S – – Valves for gas, – water and sanitary installations Copper-tin and copper- CuSn3Zn8Pb5-C CC490K – Medium-hard Thin-walled valves 90 tin-zinc casting alloys structural material; (wall thickness up to 12 good castability; mm) suitable for appli- corrosion-resistant cations up to 225 °C. to fresh water even at raised temperatures CuSn5Zn5Pb5-C CC491K C83600 Structural material; Water and steam valve 90 good castability; bodies for applications good solderability, up to 225 °C; regular- moderate braze- duty pump housings; ability; good corro- thin-walled castings of sion resistance complex geometry CuSn7Zn4Pb7-C CC493K C93200 Medium-hard Moderate-duty plain 70

Copper casting alloys alloys casting Copper material with bearings good anti-seizure properties CuSn5Zn5Pb2-C CC499K – Structural material; Fittings, valves and 90 good castability; pump housings par- good solderability, ticularly for drinking moderate braze- water applications ability; good corrosion resistance CuPb10Sn10-C CC495K C93700 Good self-lubricat- Plain bearings with 80 ing properties high surface pressure Copper-lead and copper- CuSn7Pb15-C CC496K CC93800 – Plain bearings; com- 80 tin casting alloys posite bearings

Table 21b: Machinability classification of standardized copper-based materials Machinability group I: Copper alloys with excellent machining properties

50 | DKI Monograph i.18 Alloy group Material Machinability and Typical applications Machinability processability rating Designation Number Number (EN) (UNS)

Low-alloyed copper alloys CuBe2 CW101C C17200 – High-strength parts 20 (alloying elements < 5 %) CuCo2Be CW104C C17500 High-temperature Resistance welding 40 – hardenable in cold- stability electrodes worked state CuCr1Zr CW106C C18150 High-temperature Resistance welding 20 Standard does stability electrodes; contact not define state elements for stamped, cold formed material CuNi1Si CW109C – – Heavy-duty screws, – nuts and bolts; roller bearing cages; spray nozzles; bearing bushes, applications for hardened states CuNi2Si CW111C C64700 High tensile In hardened state – strength CuNi3Si1 CW112C C70250 High tensile Mould inserts – strength Low-alloyed copper alloys CuSi3Mn1 CW116C C65500 – – 30 (alloying elements < 5 %) – non-age-hardenable Copper-tin alloy CuSn5Pb1 CW458K C53400 – – 70 Binary copper-zinc alloys CuZn36 CW507L C27200 Main alloy for cold Deep-drawn parts – working

Wrought copper alloys alloys copper Wrought CuZn37 CW508L C27400 Good solderability, Screws; hollow riveting 35 weldability and cold workability CuZn40 CW509L C28000 – Clock and watch cases 40 Multi-component copper- CuZn31Si1 CW708R C69800 For sliding loads Bearing bushes; guides – zinc alloys CuZn35Ni3Mn2AlPb CW710R – – Marine propeller shafts – CuZn37Mn3Al2PbSi CW713R – Structural material Synchronizer rings; – of high strength for plain bearings; valve sliding applications bearings; gear components; piston rings CuZn38Mn1Al CW716R – Structural material Plain bearings; sliding – of medium strength elements for sliding applications CuZn39Sn1 CW719R C46400 – Tube plates for 30 condensers; marine propeller shafts CuZn40Mn2Fe1 CW723R – – Valves; damper bars –

Table 22a: Machinability classification of standardized copper-based materials Machinability group II: Copper-based materials with good to moderate machining properties

DKI Monograph i.18 | 51 Alloy group Material Machinability and Typical applications Machinability processability rating Designation Number Number (EN) (UNS)

Copper-zinc casting CuZn16Si4-C CC761S C87800 High-strength High-strength and 40 alloys parts for electrical thin-walled parts for engineering electrical engineering applications applications CuZn25Al5Mn4Fe3-C CC762S C86100 – Worm wheel rims; 30 inner parts of high- pressure valves CuZn32Al2Mn2Fe1-C CC763S –– – – CuZn34Mn3Al2Fe1-C CC764S – – Valve parts; control – elements; taper plugs CuZn37Al1-C CC766S –– Permanent mould – castings for precision engineering applica-

Copper casting alloys alloys casting Copper tions CuZn38Al-C CC767S –– Permanent mould cast- – ings for electrical and mechanical engineering applications Copper-tin casting alloy CuSn11Pb2-C CC482K – Good anti-seizure Heavy-duty plain – properties bearings (high permanent and impact loads)

Table 22b: Machinability classification of standardized copper-based materials Machinability group II: Copper-based materials with good to moderate machining properties

52 | DKI Monograph i.18 Alloy group Material Machinability and Typical applications Machinability processability rating Designation Number Number (EN) (UNS)

Copper Cu-OFE CW009A C10100 Highest electrical Vacuum and electronic 20 conductivity applications Cu-HCP CW021A – High electrical Slip rings for electric – conductivity; good motors weldability and brazeability Cu-DHP CW024A C12200 Good weldability Fuel and oil pipes 20 and brazeability Low-alloyed copper alloys CuAg0,10 CW013A C11600 – Contacts; commutator 20 – non-age-hardenable rings CuAg0,1P CW016A – Good solderability, Contacts; commutator – brazeability and rings weldability CuSn0,15 CW117C C14200 – Connector pins 20 Low-alloyed copper alloys CuBe1,7 CW100C C17000 – – 20 (alloying ele-ments < 5 %) CuBe2 CW101C C17200 – High-strength springs 20 – hardenable in cold- CuCo2Be CW104C C17500 High-temperature Resistance welding 40 worked and precipitation- stability electrodes hardened state CuCr1Zr CW106C C18150 High-temperature Resistance welding 20 Several states – stability electrodes; continuous variations as per the casting moulds EN 12163 standard – see unhardened state CuNi1Si CW109C Medium tensile Identical to CuNi1Si 20 strength; good electrical conductivity CuNi2Be CW110C C17510 High tensile Current carrying com- – strength; good ponents in overhead electrical conduc- lines (screws, bearing tivity bushings, contacts) CuNi2Si CW111C C64700 High tensile Bolts 30 strength CuNi2SiCr – –– Welding applications; 40

Kupfer-Knetwerkstoffe die-cast aluminium and magnesium CuNi3Si1 CW112C C70250 High tensile Mould inserts – strength CuZr CW120C C15000 – – 20 Copper-aluminium alloys CuAl5As CW300G C60800 Particularly good – 20 corrosion resistance to salt solutions CuAl8Fe3 CW303G C61400 Salt-water resist- Valve seats and com- 20 ance; resistance bustion motors to sulphuric and acetic acids; anti- magnetic CuAl10Fe3Mn2 CW306G – Engine and gear Bearing bushings, me- – parts subject to vi- chanical engineering bration and wear; and process equipment scale-resistant, applications high-strength nuts and bolts, shafts, spindles, worm drives, gear wheels CuAl10Ni5Fe4 CW307G C63000 Hard; shock re- Toggle lever bearings; 20 sistant; high load shafts; screws; wear- strength, good ing parts for combus- salt-water resis- tion engines; mould tance making CuAl11Fe6Ni6 CW308G – High tensile Journal bearings; – strength valves; forming dies

Table 23a: Machinability classification of standardized copper-based materials Machinability group III: Copper-based materials with moderate to poor machining properties

DKI Monograph i.18 | 53 Alloy group Material Machinability and Typical applications Machinability processability rating Designation Number Number (EN) (UNS)

Copper-nickel alloys CuNi25 CW350H C71300 Wear resistant; – – silver-white colour CuNi10Fe1Mn CW352H C70600 – Brake pipes; 20 intercoolers CuNi30Mn1Fe CW354H C71500 – Electrical contacts 20 Copper-nickel-zinc alloys CuNi12Zn24 CW403J C75700 Excellent Optical and precision 20 formability engineering components CuNi18Zn20 CW409J – – Spectacle frame parts; – membranes; connectors Copper-tin alloys CuSn4 CW450K C51100 – Lead frames; 20 connectors CuSn5 CW451K C51000 – Connecting rod 20 bearings CuSn6 CW452K C51900 – Gear wheels; bushings; 20 pump parts; clock/ watch components; connectors; hose tubing; Bourdon tubes CuSn8 CW453K C52100 – Worm gears; gear 20 wheels; bolts; screws; small-end bushings; rocker bearings; cotter pins CuSn8P CW459K – – Worm gear wheels; 30 gear parts; heavy- duty plain bearings; toggle levers; valve guides in exhaust gas systems; small-end bushings, cam shaft bearings; rocker bear- Wrought copper alloys alloys copper Wrought ings; hydraulic cylinder bearings; pump components Binary copper-zinc alloys CuZn5 CW500L C21000 Excellent cold Components for electri- 20 workability cal installations; rotor bars; components for the watchmaking industry CuZn10 CW501L C22000 Excellent cold Watchmaking industry 20 workability CuZn15 CW502L C23000 Excellent cold Flexible bellows 30 workability CuZn20 CW503L C24000 Excellent cold Pressure gauges 30 workability CuZn28 CW504L – Excellent cold Bellows; musical – workability instrument parts CuZn30 CW505L C26000 Excellent cold Connectors; radiator 30 workability trim CuZn33 CW506L C26800 Excellent cold – 30 workability Multi-component copper- CuZn20Al2As CW702R C68700 – Tubing condensers; 30 zinc alloys heat exchangers CuZn28Sn1AS CW706R C44300 – Heat exchanger tube 30 sheets

Table 23b: Machinability classification of standardized copper-based materials Machinability group III: Copper-based materials with moderate to poor machining properties

54 | DKI Monograph i.18 Alloy group Material Machinability and Typical applications Machinability processability rating Designation Number Number (EN) (UNS) Copper casting alloys CuCr1-C CC140C – – Welding electrode – holders; contact connectors Copper-tin CuSn10-C CC480K C90700 Salt-water proof Valve and pump bod- 20 casting alloys ies; stators, rotors and impellers for pumps and water turbines CuSn12-C CC483K C90800 Salt-water proof, Bearings for Cardan – wear resistant joints, couplers; ball- screw nuts for heavy loads; worm wheels and helical gear wheels CuSn12Ni2-C CC484K C91700 Salt-water proof, Bearings for Cardan 20 wear resistant joints, couplers; ball- screw nuts for heavy loads; worm wheels and helical gear wheels; bevel gear wheels; worm wheel rims Copper casting alloys alloys casting Copper Copper-aluminium CuAl10Fe2-C CC331G C95200 – Bevel gear wheels, syn- 20 casting alloys chronizer rings; gear selector forks and gear selector parts CuAl10Ni3Fe2-C CC332G – – – CuAl10Fe5Ni5-C CC333G C95500 Good salt-water Heavy-duty crankshaft 50 resistance bearings and toggle lever bearings; heavy- duty worm and helical gear wheels; marine propeller components Copper-nickel casting CuNi10Fe1Mn1-C CC380H C96200 – – 10 alloys CuNi30Fe1Mn1NbSi-C CC383H C96400 – – 20

Table 23c: Machinability classification of standardized copper-based materials Machinability group III: Copper-based materials with moderate to poor machining properties

DKI Monograph i.18 | 55 11 Anhang 84

11 Anhang 84 Formeln 11 Anhang 84 11BeiFormeln Anhang Zahlenwertgleichungen sind die einzusetzenden Größen mit ihren Dimensionen angege-84 ben) Formeln FormelnBei Zahlenwertgleichungen 12 sind dieM einzusetzendenathematical Größen formula mit ihren Dimensionen angege- 1)11ben) GeometrischeAnhang Beziehung zwischen Frei-, Keil- und Spanungswinkel: 84 Bei Zahlenwertgleichungen sind die einzusetzenden Größen mit ihren Dimensionen angege- Bei11 AnhangZahlenwertgleichungen sind die einzusetzenden Größen mit ihren Dimensionen angege-84 1)ben) Geometrische Beziehung zwischen Frei-, Keil- und Spanungswinkel: ben)Formeln o + o + o = 90° (1) 1)Formeln Geometrische Beziehung zwischen Frei-, Keil- und Spanungswinkel: 2) Spandickenstauchung: o + o + o = 90° (1) 1)Bei Geometrische Zahlenwertgleichungen Beziehung sind zwischen11 die Anhang einzusetzenden Frei-, Keil- undGrößen Spanungswinkel: mit ihren Dimensionen angege- 85 Beiben) Zahlenwertgleichungen sind die einzusetzenden Größen mit ihren Dimensionen angege- 2) Spandickenstauchung:12.1. o + Equations o + o = 90° where: (1) 14) Feed power: ho + o + o = 90° (1) 11 Anhang 86 ben) In numericalch 7)> 1C T, Cequations,v und k sindthe dimen- kennzeichnende T : (2) T ool lifeGrößen in minutes der Schnittbedingungen: sionsh of the quantities to be entered P = F v (14) 1) Geometrische Beziehung zwischen Frei-, Keil- und Spanungswinkel:11 Anhang f f ⋅ f 86 2) Spandickenstauchung:are h given. v Cutting1 speed in metres per 2) Spandickenstauchung: ch c 15) Netto-Antriebsleistung: >1 (2) k 1) Geometrische Beziehung zwischen Frei-, Keil- und Spanungswinkel:T =minuteCC (7) 15) Net machine power: 3) Spanbreitenstauchung h 1)h Geometricalo + o + o relationship = 90° between (1) 15) Netto-Antriebsleistung:11 Anhang 86 theh ch clearance,1 wedge and rake angles f Feed in mm per revolution vF ch 8)> Erweiterten Taylor-Gleichungen: (2) 'P cc (15) oh + > 1o + o = 90° (2) (1) è = (15) 3) Spanbreitenstauchung(tool-in-hand bh reference system): 60000 2) Spandickenstauchung: ch 15) Netto-Antriebsleistung:vF 1 ap Depth of cut in mm cc > (3) 'P = (15) αob + βo + γo = 90° (1) C Pe’ è Ne t machine power in kW 2)3) Spandickenstauchung:Spanbreitenstauchung = 1 60000 b T k Gradientc of the straight line in (8) 3) Spanbreitenstauchung h ch ca Pe’ f Netto-Antriebsleistungk in kW vF ch 1 11 Anhang cc 86 2) Chip> thickness1 compression: (3) the tool-life vfa c plot Fc Cutting force'P in N b > (2) è = (15) hh (kFc = tan α Schnittkraft) in N 60000 b ch 1 Pe’ Netto-Antriebsleistung15) Netto-Antriebsleistung: in kW b ch >1 (2) (2) v Schnittgeschwindigkeitv inc m/min60000 Cutting speed in metres Konstante per in N m/kW min hch Darin> bedeuten: T: Werkzeugstandzeit (3) c in min b >1 C1 (3) Dimensioned,Fc Schnittkraft empirically in N minute 4) Geradengleichung b vc Schnittgeschwindigkeit in m/min 3) Spanbreitenstauchung determined constantPe’ Netto-Antriebsleistung in kWvF vc Schnittgeschwindigkeit in m/min60000 cc Konstante in N m/kW min 3) Chip width compression: f Vorschub16) (proÜberschlagsformel Umdrehung ) in mm für 60000 die ConversionNetto-Antriebsleistung'P = factor in (N • m)/ (15) bei mehrschneidigen Spa- 3) Spanbreitenstauchung Fc Schnittkraft in N è 60000 ap SchnitttiefeC Dimensionless in mm constant: (kW • min) 4) Geradengleichung b = + nxmy a (4) nungswerkzeugen: ch k Steigunge16)xponent der Überschlagsformel Geraden of thevc depth im Schnittgeschwindigkeit ofStandzeitdiagramm cut für die Netto-Antriebsleistung (k in= tanm/min60000 ) Konstantebei mehrschneidigen in N m/kW min Spa- >1 (3) (3) bb C1 dimensionsbehaftete,nungswerkzeugen: Pempirische’ Netto-Antriebsleistung ermittelte16) Approximate Konstante in kW net machine power for 4) Geradengleichung ch= 1 + C (4) Dimensionless constant: multipoint tools: 4) Geradengleichung > nxmy Ca dimensionslosef (3) Konstante:F SchnittkraftExponent in der N SchnitttiefeV 5) Taylor Gerade : Logarithmischeb vc-T-Abhängigkeit: 16) Überschlagsformelc fürw die Netto-Antriebsleistung bei mehrschneidigen Spa- 4) Equation of a straight line: exponent of the feed 'P è = (16) Cf dimensionslose Konstante:vc SchnittgeschwindigkeitExponent des Vorschubs in m/min60000 Konstante in N m/kW min nungswerkzeugen: Vwp = + nxmy (4) Vw 5) Taylor Gerade : Logarithmische= 9) Schnittkraftformel+ vnxmy c-T-Abhängigkeit: += (4) vlogkClogTlog nach Kienzle/Victor:9) (4) (5)Cutting force formula (Kienzle/ 'P = (16) (16) v c è Victor): 16) Überschlagsformel fürVwp die Netto-Antriebsleistung bei mehrschneidigen Spa- 4) Geradengleichung 5) E quation of Taylor tool-life plot V 5) Taylor Gerade : Logarithmische v -T-Abhängigkeit: Pe’ Netto-Antriebsleistungnungswerkzeugen: in kW w c ()m1 c 'P = 5) Taylor Gerade : Logarithmische(log-log plot v -T-Abhängigkeit: ofv += vc vs. T): vlogkClogTlog c (5)= khbF (9) (9) P Net machineè3 power in kW (16) 4) Geradengleichung c c V Zerspantes1.1c Werkstoffvolumene’ in cm /minV Pw’ Netto-Antriebsleistung in kW wp = + nxmy (4) e 3 Vw += vlogkClogTlog (5) Fc (5)Cu Vwptting force Spezifisches in N ZerspanvolumenVw S tock in removal'P cm= 3/min rate (volumekW of (16) v += c Vw Zerspantes Werkstoffvolumen in ècm /min 6) Taylor-Funktion: =Fc + Schnittkraftnxmy v vlogkClogTlog inc N (5) (4) workpieceV materialwp removed per Pe’ Netto-Antriebsleistung in kW3 3 6) Taylor function: b CVhipwp width Spezifisches in mm Zerspanvolumenunit intime cm in /mincm /min) kW 5) Taylor Gerade : Logarithmischeb v Spanungsbreitec-T-Abhängigkeit: in mm 17) Spezifisches Spanungsvolumen (spezifische Spanungsleistung):3 k Vw Zerspantes Werkstoffvolumen in cm /min 6) Taylor-Funktion: Pe’ Netto-Antriebsleistung in kW 5) Taylor Gerade : Logarithmische=h vCT cv v Spanungsdickec -T-Abhängigkeit: (6) in mm h (6)Undeformed chip thickness Vwp Specific stock removal 3 Vwp Spezifisches Zerspanvolumen 3in cm /min kW in17) mm SpezifischesVw Spanungsvolumen Zerspantes Werkstoffvolumenrate • (spezifischevolume in cmof workpiece/min Spanungsleistung): ma- 1-mc dimensionsloserv += vlogkClogTlog c Anstiegswert (5) der spezifischen SchnittkraftV vA vA 1 6) Taylor-Funktion: where: k V Spezifischesw Zerspanvolumenterialc removed in cm perc3/min unit kWtime and Darin bedeuten: T: Standzeit= in minvCT (6) wp V2 wp == = = (17) 6) Taylor-Funktion: T: kTc1.1ool lifecv Hauptwertin minutes der spezifischen1-m Schnittkraft Dimensionless in index N/mm reflecting per unit of power supplied v += vlogkClogTlog c (5)c 17) SpezifischesPc Spanungsvolumen vF cc c vAk (spezifischek cc Spanungsleistung): V vA 3 vA 1 vc: Schnittgeschwindigkeitvc: Cutting speed in m/min in m/min the increase of the specific w in cmc /(min • kW)c ) k 17) SpezifischesVwp Spanungsvolumen== = (spezifische= Spanungsleistung): (17) Darin bedeuten: T: Standzeit= in minvCT cv k (6)cutting force k: Steigung=10) der ÜberschlägigevCT Geraden im Standzeitdiagramm Größe der Vorschubkraft: (k = tan( )) Pc vF cc c vAk k cc k: Gr adientcv of the straight line in (6) 18) Spezifisches Spanungsvolumen17) SpecificV (Zahlenwertgleichung):stock removal vA rate: vA 1 vc: Schnittgeschwindigkeit in m/min 2 w c c 6) Taylor-Funktion: Cv: Standzeitthe Ttool-life für vc plot= 1 (km/min. = tan( α)) kc1.1 Specific cutting force in N/mm Vwp Vw == vA c = vA c 1 = (17) Darin bedeuten: T: Standzeit in min Vwp P== = vF = vAk (17) k (17) Darin bedeuten: T:k: StandzeitSteigung derin min Geraden im Standzeitdiagramm 18) (k Spezifisches = tan()) Spanungsvolumen c(Zahlenwertgleichung): cc c cc Ff 0,3 Fc (10) Pc vF cc c vAk k cc 6) Taylor-Funktion: vc: SchnittgeschwindigkeitC : Tool life T for unit cutting in m/min speed 10) Approximate magnitude of feed V 60000 v k w v Ccv: :Schnittgeschwindigkeit Standzeit T für vc = 1 m/min. in m/min V == (18) Durch Umstellen der Taylor-Gleichung= (vc = 1vCT m/min.)cv ergibt sich force: (6) wp k: Steigung der Geraden im Standzeitdiagramm (k = tan(18))) SpezifischesPc Spanungsvolumen18) Numericalk c equation for(Zahlenwertgleichung): specific k: Steigung11) der1 Überschlägige Geradenk im Standzeitdiagramm Größe von Vorschub- (k = tan( und) )Passivkraft: 18) Spezifisches V Spanungsvolumen60000 (Zahlenwertgleichung): 11 Anhang = vCT (6) V 85 w stock== removal rate: Cv: StandzeitThe Taylor kT equation CTv fürcv vc = can1 m/min. be rearranged Ff ≈ 0,3 Fc (10) wp (18) DurchDarin bedeuten:Umstellen der C T:Taylor-Gleichungv :Standzeit Standzeitc = in T minfürT vergibt c = 1 sichm/min. (6a) P k to yield: c Vc 600003 1 Vwp spezifische SpanungsleistungwV inw cm60000/min Kw vc: Schnittgeschwindigkeit in m/min F11)P Approximate Ff 0,3 F magnitudec of feed (11)and Vwp == (18) 11 Anhang7)Darin CT, Cbedeuten: v und k sind T:kennzeichnende Standzeit ink min Größen der Schnittbedingungen: 85 Vwp == (18) (18) Durch Umstellen der Taylor-Gleichung= CTv ergibt (6a) sich passive (6a) force: Pc k c3 c T Vw zerspantes Werkstoffvolumen Pinc cm3/mink c Durch Umstellen der vk:Taylor-Gleichungc :Steigung Schnittgeschwindigkeit der Geraden ergibt sichim in Standzeitdiagramm m/min Vwp (k = tan( spezifische)) Spanungsleistung in cm /min Kw 1 1 12)1 Wirkleistung: Pc Schnittleistung in kW 3 7) C T, Cv und k sind kennzeichnende Cv: Standzeit7) CT, Cv and kT Größenfür k are kvc quantities= 1der m/min. Schnittbedingungen: that FP ≈ Ff ≈ 0,3 Fc (11) Vwp Spe cific stock removal3 rate in k: Steigung= der CTv CC Geraden im Standzeitdiagramm (6a)V w (k = tan( zerspantes)) Vwp Werkstoffvolumen spezifische Spanungsleistung in cm /minin cm /min Kw characterizec Tk=CTv theT cutting conditions: (7) cm3/(min2 • kW) 3 c = T (6a)k c spezifischeVwp spezifische Schnittkraft Spanungsleistung in N/mm 3in cm /min Kw 1 Vw zerspantes Werkstoffvolumen in cm /min Cv: Standzeit T für vc = 1 m/min. 12) EffectivePc cutting Schnittleistung power: in3 kW 2 Pe = Fe ve = Pc + Pf (12) 3 8) Erweiterten Taylor-Gleichungen:CC k (7) 60000 KonstanteVw P in zerspantes cm Schnittleistung N/mm WerkstoffvolumenV in kWS mintock removal2 kW rate in in cm cm3/min/min Durch Umstellen der Taylor-GleichungT = ergibt sich (7) kc spezifischec Schnittkraft win N/mm 2 1 Pe = Fe ⋅ ve = Pc + Pf (12)k spezifische3 Schnittkraft2 in N/mm Durch Umstellen der Taylor-Gleichung8) Extended Taylor ergibt equation: sich 60000 KonstantePc c Schnittleistungin cm N/mm in min kW kW k Pc 3 Cutting2 power in kW2 8) Erweiterten Taylor-Gleichungen:c =13) Schnittleistung:CTv T (6a)19) Theoretische60000 Rautiefe: Konstante in cm N/mm min kW 1 C1 13) Cutting power: kc spezifische Schnittkraft in N/mm T = (8) (8) 2 ck c f k k 3 Specific cutting2 force in N/mm c = a CTv T (6a) 60000 Konstante in ccm N/mm min kW vfa c 19) Theoretische Rautiefe: Pc = Fc ⋅ v c (13) 19) Theoretische Rautiefe: 2 C1 Pc = Fc vc (13) f T = (8) = rrR 2 ca c f k th,t (19) Darin bedeuten: T: Werkzeugstandzeit vfa c in min 19) Theoretische Rautiefe:42 2 2 f 2 f vc 56 Schnittgeschwindigkeit| DKI14) Monograph Vorschubleistung: i.18 in m/min = rrR th,t = rrR th,t (19)(19) f Vorschub (pro Umdrehung ) in mm 4 4 Darin bedeuten: T: Werkzeugstandzeit in min 2 20) Theoretische Tautiefe, überschläglich:2 f vc ap Schnittgeschwindigkeit Schnitttiefe in mm in m/min Pf = Ff v f (14) = rrR (19) k Steigung der Geraden im Standzeitdiagramm (k = tan20) )Theoretische Tautiefe,th,t überschläglich: f Vorschub (pro Umdrehung ) in mm 20) Theoretische Tautiefe, überschläglich: 4 ap C1 Schnitttiefe dimensionsbehaftete, in mm empirisch ermittelte Konstante k Ca Steigung dimensionslose der Geraden Konstante: im Standzeitdiagramm Exponent der Schnitttiefe (k = tan ) 20) Theoretische Tautiefe, überschläglich: C1 Cf dimensionsbehaftete, dimensionslose Konstante: empirisch Exponent ermittelte des Konstante Vorschubs 9) SchnittkraftformelCa nach dimensionslose Kienzle/Victor: Konstante: Exponent der Schnitttiefe Cf dimensionslose Konstante: Exponent des Vorschubs

9) Schnittkraftformel nach Kienzle/Victor:() m1 c khbF c = 1.1c (9)

()m1 c khbF c = 1.1c (9) Fc Schnittkraft in N b Spanungsbreite in mm Fc h Schnittkraft Spanungsdicke in N in mm b Spanungsbreite in mm 1-mc dimensionsloser Anstiegswert der spezifischen Schnittkraft h Spanungsdicke in mm 2 kc1.1 Hauptwert der spezifischen Schnittkraft in N/mm 1-mc dimensionsloser Anstiegswert der spezifischen Schnittkraft 2 kc1.110) HauptwertÜberschlägige der spezifischen Größe der Vorschubkraft:Schnittkraft in N/mm

10) Überschlägige Größe der Vorschubkraft: Ff 0,3 Fc (10)

11) Überschlägige GrößeF vonf 0,3 Vorschub- Fc und Passivkraft: (10)

11) Überschlägige Größe von Vorschub- und Passivkraft: FP Ff 0,3 Fc (11)

12) Wirkleistung: FP Ff 0,3 Fc (11)

12) Wirkleistung: Pe = Fe ve = Pc + Pf (12)

13) Schnittleistung: Pe = Fe ve = Pc + Pf (12)

13) Schnittleistung: Pc = Fc vc (13)

14) Vorschubleistung: Pc = Fc vc (13)

14) Vorschubleistung: Pf = Ff v f (14)

Pf = Ff v f (14) 11 Anhang 86

15) Netto-Antriebsleistung:

vF 'P = cc è 60000 (15)

Pe’ Netto-Antriebsleistung in kW

Fc Schnittkraft in N vc Schnittgeschwindigkeit in m/min60000 Konstante in N m/kW min

16) Überschlagsformel für die Netto-Antriebsleistung bei mehrschneidigen Spa- nungswerkzeugen:

Vw 'P è = (16) Vwp

Pe’ Netto-Antriebsleistung in kW 3 Vw Zerspantes Werkstoffvolumen in cm /min 3 Vwp Spezifisches Zerspanvolumen in cm /min kW

17) Spezifisches Spanungsvolumen (spezifische Spanungsleistung):

Vw vA c vA c 1 Vwp == = = (17) Pc vF cc c vAk k cc

18) Spezifisches Spanungsvolumen (Zahlenwertgleichung):

Vw 60000 Vwp == (18) Pc k c

3 Vwp spezifische Spanungsleistung in cm /min Kw 3 Vw zerspantes Werkstoffvolumen in cm /min

Pc Schnittleistung in kW 2 kc spezifische Schnittkraft in N/mm 3 60000 Conversion factor in cm • N/ nWT Number of parts machined in one where: 23 2 60000 Konstante in(mm cm • minN/mm • kW) (=min N • m/(kWkW • min)) tool life hz = Undeformed chip thickness per tooth and revolution 19) Theoretically achievable peak-to- 24) Total cost of manufacturing one 19) Theoretische Rautiefe: valley roughness: part: fz = F eed per tooth and revolution

2 K1 = th1 ⋅ R + Kfix + KW1 = Kth1 + Kfix + KW1 (24) κ = Tool cutting edge angle 2 f th,t = rrR (19) (19) 11 Anhang where: 87 ϕs = Angle of cutter engagement 4 11 Anhang 20) Approximate expression for theo- K Total fabrication cost per unit 87h = Average thickness of f 2 1 m 20) Theoretische Tautiefe,reticallyR achievable überschläglich: peak-to-valley product(20) in € undeformed chip 11 Anhang roughness:th,t 87 r8 2 f th1 Machining time per part in ap = Depth of cut (feed) R th,t (20) 11 Anhang 2r8 minutes 87 f a = Working engagement 21) Theoretisch einzustellenderR th,t Vorschub (20) bei vorgegebener Rautiefe(20) und vorgegebe- r8 Kfix F ixed costs in € (independent of (radial depth of cut) nem Eckenradius: f 2 21) Theoretisch einzustellenderR Vorschub bei vorgegebenercutting Rautiefe speed vc) und vorgegebe- 21) Theoreticalth,t feed setting required for (20) D = Diameter of milling cutter r8 21)nem Theoretisch Eckenradius: einzustellender a specified peak-to-valley Vorschub roughness bei vorgegebener Kth1 Machining Rautiefe costs inund € vorgegebe- and a given Rr8f nose radius: (21) nem Eckenradius: th,t 21) Theoretisch einzustellender Vorschub bei vorgegebenerR Cost rate forRautiefe operator undand vorgegebe- Rr8f th,t (21) machine(21) (excluding tool costs) 32)nem Werkzeugkosten Eckenradius: je Standzeit: in €/min 22) Tool costs Rr8f per th,t tool life: (21) 11 Anhang 88 32) Werkzeugkosten je Standzeit: 25) Cost-optimized tool life: K Rr8f K Wa th,t KK (22) (21) 32) Werkzeugkosten je WTStandzeit: Ww ()++= Ws (22) n K)1k( WT KT 11 Anhang T = (25) 88 K Wa11 Anhang KK oK (25) 88 32) Werkzeugkostenwhere: WTje Standzeit: Ww ()++= Ws (22)R Kn T KWT Tool costsWa per tool life in € worin bedeuten K ()++= KK K)1k( WT WT Ww Ws where: (22) K)1k( WT n ToK == (25) TKworin bedeuten ToK (25) KWa Purchase priceWa of tool in € ToK = C ost-optimizedRR tool life in min worin bedeuten K WT Ww ()++= KK Ws (22) K Werkzeugkosten je StandzeitT inoK = kostenoptimale Standzeit in min WT n T worin bedeuten nT Number of–k tool lives = per tool Steigungswert –k = der Gradient logarithmischen of straight line inv -T-Funktion KWa Anschaffungskosten (fordes solid Werkzeugs worinworinshank toolsbedeutenbedeuten in or brazed tool-life plot c KWT Werkzeugkosten je Standzeit in n Anzahl der Standzeiteninserts: (bei n WendeplattenTTK oK=WT number = = of regrinds; Anzahl kostenoptimale Werkzeugkosten der Schneidkanten) Standzeit je Standzeit in min nach Gleichung (22) in T ToK = kostenoptimale Standzeit in min KWaworin Anschaffungskosten bedeuten for des indexable Werkzeugs cutting ininserts; K = Tool costs per tool life in € as KWT Werkzeugkosten je Standzeit in WT KWw Kosten für das Wechseln des–kR verschlissenen = = SteigungswertRestkostensatz, Werkzeugs in der d.h. logarithmischen Kostensatz des vc-T-Funktion Arbeitsplatzes ohne Werkzeugkosten in n Anzahl der StandzeitennT = number(bei–k Wendeplatten of cutting = edges SteigungswertAnzahl der Schneidkanten) derdefined logarithmischen in Eq. (22) vc-T-Funktion KTWa Anschaffungskosten des Werkzeugs in K Kosten für das Nachschleifenper insert)K desWT/min Werkzeugs = Werkzeugkosten (entfällt bei Wendeplatten) je Standzeit in nach Gleichung (22) in WsKWT Werkzeugkosten je StandzeitKWT in = Werkzeugkosten je Standzeit nach Gleichung (22) in KWw Kosten für das Wechseln des verschlissenen WerkzeugsR = Cinost rate for operator and nT Anzahl der Standzeiten (beiR Wendeplatten = Restkostensatz, Anzahl der Schneidkanten) d.h. Kostensatz des Arbeitsplatzes ohne Werkzeugkosten in KWa AnschaffungskostenK Cost indes € associatedR Werkzeugs = with in Restkostensatz, machine d.h. Kostensatz (excluding tool des costs) Arbeitsplatzes ohne Werkzeugkosten in KWs Kosten für das NachschleifenWechselnWw des26) desverschlissenen Spanungsdicke Werkzeugs Werkzeugs(entfällt beim beiStirnfräsen: inWendeplatten) in 23)Ww Werkzeugkosten je Werkstück:changing the /min worn tool in €/min nT Anzahl der Standzeiten (bei/min Wendeplatten Anzahl der Schneidkanten) KWs Kosten für das Nachschleifen des Werkzeugs (entfällt bei Wendeplatten) in K Kosten für das Wechseln des verschlissenen Werkzeugs in 23) WerkzeugkostenWw jeKWs Werkstück: Cost in € for regrinding the tool 26) Undeformed6,114 ° chip thicknessa in face KWT 26) Spanungsdicke beim Stirnfräsen: e K Kosten fürK das Nachschleifen(not applicable26) Spanungsdicke ifdes indexable Werkzeugs in- beim(entfälltmillingh m =Stirnfräsen: operations: bei Wendeplatten)z sinf () in (26) Ws W1 = (23) 23) Werkzeugkosten je Werkstück:serts are used) s ° D zT KWT KW = 6,114 ° a e 23) Werkzeugkosten123) Toolje Werkstück: costs for fabricating one part: 6,114 °(23) a e Kz h m = z sinf () (26) WTT 27) Spanungsdicke beimh m =Umfangfräsen:z sinf () (26) (26) K = s °° DD wobei bedeuten W1 z s (23) T K K WT 27) Undeformed chip thickness in wobei bedeuten W1 = (23) 6,114 ° (23)a KW1 Werkzeugkosten je Werkstückz 27) in Spanungsdicke beimperipheral Umfangfräsen: milling operations:e T 27) Spanungsdicke beimhm =Umfangfräsen:fz (27) wobei bedeuten ° D s KW1 Werkzeugkostenwhere: je Werkstück in nWT Standmenge, d.K h. Menge Tool costs der in je € Standzeitfor fabricating bearbeiteten one Werkstücke6,114 ° ae W1 6,114 ° ae wobei bedeuten hm = fz (27) (27) KW1 Werkzeugkosten je Werkstückpart in hm = fz (27) Dabei bedeuten s °° DD nWT24) Bearbeitungskosten Standmenge, d. h. je Menge Werkstück: der je Standzeit bearbeiteten Werkstückes K Werkzeugkosten je Werkstückhz in = Spanungsdicke je Schneide und Umdrehung n W1 Standmenge, d. h. Menge der je Standzeit bearbeiteten Werkstücke WT f = Vorschub je Schneide und Umdrehung 24) Bearbeitungskosten je Werkstück:DabeiDabeiz bedeutenbedeuten K1 = th1 R + Kfix + KW1 = Kth1 + Kfix + KW1 (24) DKI Monograph i.18 | 57 nWT Standmenge, d. h. Mengehz der je == Standzeit SpanungsdickeEinstellwinkel bearbeiteten je Werkstücke Schneide und Umdrehung 24) Bearbeitungskosten je Werkstück:hz = Spanungsdicke je Schneide und Umdrehung K = t R + K fz s+ K = == K + VorschubFräserschnittwinkel K + K je Schneide (24) und Umdrehung 1 h1 fixfz W1 = th1 Vorschubfix W1 je Schneide und Umdrehung worin24) bedeutenBearbeitungskosten je Werkstück: h m = = Einstellwinkel mittlere Spanungsdicke K1 = th1 R + Kfix + KW1 == Kth1 +Einstellwinkel Kfix + KW1 (24) K1 Spanungskosten je Werkstück in worin bedeuten a = Schnitttiefe(Zustellung) sp == FräserschnittwinkelFräserschnittwinkel th1 Spanungszeit desK =Werkzeugs t R + K sje Werkstück + K = K in min + K + K (24) K1 Spanungskosten1 je Werkstückh1 a fix in =W1 th1Eingriffsgrößefix W1 worin bedeuten hm = mittlere Spanungsdicke Kfix Fixkosten (unabhängig von vch)m in = mittlere Spanungsdicke th1 Spanungszeit des WerkzeugsD je Werkstück = Fräserdurchmesser in min K1 Spanungskosten je Werkstückaap in = = Schnitttiefe(Zustellung) Schnitttiefe(Zustellung) Kth1worin Hauptzeitkosten bedeuten in p Kth1fix SpanungszeitFixkosten (unabhängig des Werkzeugs von av c) jein Werkstück= Eingriffsgröße in min R Restkostensatz, d. h. Kostensatza des= Arbeitsplatzes Eingriffsgröße ohne Werkzeugkosten in /min K K 1 Hauptzeitkosten Spanungskosten in je Werkstück in Kfixth1 Fixkosten (unabhängig von DDvc ) in = = FräserdurchmesserFräserdurchmesser R th1 Restkostensatz, Spanungszeit d. des h. KostensatzWerkzeugs11.2 desje Formelzeichen, Werkstück Arbeitsplatzes in min ohne Symbole Werkzeugkosten und Abkürzungenin /min K25)th1 Kostenoptimale Hauptzeitkosten Standzeit: in Kfix Fixkosten (unabhängig von vc) in R Restkostensatz, d. h. Kostensatz des Arbeitsplatzes ohne Werkzeugkosten in /min 25) KKostenoptimaleth1 Hauptzeitkosten Standzeit: in 11.2Größe Formelzeichen, Einheit Symbole und AbkürzungenBezeichnung 11.2 Formelzeichen, Symbole und Abkürzungen 25) RKostenoptimale Restkostensatz, Standzeit: d. h. Kostensatz des Arbeitsplatzes ohne Werkzeugkosten in /min ap mm Schnitttiefe GrößeGröße EinheitEinheit BezeichnungBezeichnung 25) Kostenoptimale Standzeit:

ae Mm Eingriffsgröße ap mm Schnitttiefe ap mm Schnitttiefe

A mm2 Spanungsquerschnitt ae Mm Eingriffsgröße ae Mm Eingriffsgröße

ABS - 2 Aufbauschneide AA mmmm2 SpanungsquerschnittSpanungsquerschnitt

A5 % Bruchdehnung ABSABS - - AufbauschneideAufbauschneide

A5 % Bruchdehnung A5 % Bruchdehnung 12.2 symbols and abbreviations

Symbol or Unit Name/Description abbreviation

ap mm Depth of cut

ae mm Working engagement (radial depth of cut) A mm2 Area of uncut chip

ABS - Built-up edge

A5 % Elongation after fracture b mm Undeformed chip width

bch mm Chip width

bf mm Width of chip breaker

Ca - Constant in the extended Taylor equation: exponent of the depth of cut

Cf min Constant in the extended Taylor equation: exponent of the feed

CT m/min Constant in the Taylor equation: ∧ vc when T = 1 min

Cv min Constant in the Taylor equation: ∧ T when vc = 1 m/min

C1 dimensioned Constant in the extended Taylor equation d mm Diameter (of drill hole, drill, milling cutter etc.)

ε % Degree of deformation

E N/mm2 Modulus of eleasticity

f mm/U Feed per revolution

fh - Correction factor that accounts for the influence of the uncut chip thickness on the cutting force

fz mm/tooth Feed per tooth F N Total cutting force

Fa N Active force

Fc N Cutting force

Fc,n N Perpendicular (normal) cutting force

Fe N Effective force

Fe,n N Perpendicular (normal) effective force

Ff N Feed force

Ff,n N Perpendicular (normal) feed force

Fn N Perpendicular (normal) force

Fp N Passive force

Ft N Tangential force h mm Undeformed chip thickness

hch mm Chip thickness

hc,1 mm Normalized uncut chip thickness, hc,1 = 1mm

hf mm Depth of chip breaker

hm mm Average thickness of undeformed chip

hmin mm Minimum thickness of undeformed chip

hz mm/tooth Uncut chip thickness per tooth HB - Brinell hardness

HM - Carbide

HM-PCD - Carbide with polycrystalline diamond coating

HSS - High-speed steel

58 | DKI Monograph i.18 Symbol or Unit Name/Description abbreviation HV - Vickers hardness

HRC - Rockwell hardness k - Gradient of straight line in Taylor tool-life plot

2 kc N/mm Specific cutting force

2 kc1.1 N/mm Principal value of the specific cutting force K - Crater ratio

KB mm Crater width

KL mm Crater lip width

KM mm Distance of centre of crater from tool edge

KT mm Crater depth

Kfix € Fixed costs (independent of cutting speed)

KM dimensioned Constant; dependent on type of drill, tool material and work material

Kth1 € Machining time costs

KWa € Purchase price of tool

KWs € Tool regrinding costs

KWT € Tool costs per tool life

KWw € Costs associated with changing the worn tool

KW1 € Tool costs per tool

K1 € Total fabrication costs per unit product L mm Hole depth, length of drilled hole

MD Nm Torque n rev./min Spindle speed, rotational speed Number of tool lives nT - (for a solid tool nT = 1; for an indexable cutting insert nT = number of cutting edges) p bar Pressure

Pc kW Cutting power

Pe kW Effective cutting power

Pe’ kW Net machine power

Pf kW Feed power re mm Nose radius of cutting tool R €/min Cost rate for operator and machine

Ra µm Mean roughness depth

2 Re N/mm Yield point

2 Rm N/mm Tensile strength

2 Rp0,2 N/mm 0.2 % yield strength

Rt µm Maximum roughness depth

Rt,th µm Theoretically achievable peak-to-valley roughness SV mm Displacement of cutting edge

SVα mm Flank-side displacement of cutting edge

SVγ mm Face-side displacement of cutting edge t min Cutting time th1 min Cutting time of tool per part

DKI Monograph i.18 | 59 Symbol or Unit Name/Description abbreviation T min Tool life

ToK min Cost-optimized tool life

vc m/min Cutting speed

ve m/min Resultant cutting velocity

vf m/min Feed velocity

voK m/min Cost-optimized cutting speed

vot m/min Time-optimized cutting speed V mm3 Wear volume

VB mm Width of flank wear land

Q cm3/min Material removal rate or stock removal rate (volume of work material removed per unit time)

3 VwP cm /min ⋅ kW Specific stock removal rate (material removal rate per unit of machine power)

Wc N ⋅ m Cutting energy x mm Height offset, height mismatch

z - Number of teeth on milling cutter

nWT - Number of workpieces machined per tool life α degree Helix angle of straight line

αo degree Orthogonal clearance (or relief) angle

αf degree Chamfer clearance (or relief) angle

αn degree Minor flank clearance (or relief) angle

αx degree Side clearance (or relief) angle

βo degree Orthogonal wedge angle

βf degree Chamfer wedge angle

βx degree Side wedge angle

γo degree Orthogonal rake angle

γf degree Chamfer rake angle

γx degree Side rake angle ε degree Tool included angle

εo % Degree of deformation in the shear plane

κ r degree Cutting edge angle

κn degree Minor cutting edge angle λ degree Cutting edge inclination

σ degree Drill point angle

τ da N/mm2 Shear strength

ϕ degree Angle of feed motion

ϕ degree Angle of approach of milling cutter teeth

ϕs degree Angle of cutter engagement ψ degree Chisel edge angle

ω 1/s Angular velocity

60 | DKI Monograph i.18 13 References

[1] [10] [17] Thiele Jr., Eugene W.; Kundig, Kienzle, O.: Die Bestimmung von Djaschenko: Die Beschaffenheit der Konrad J.A.: Comparative Machinability Kräften und Leistungen an spanenden Oberfläche bei der Zerspanung mit of Brasses Steels and Aluminum Alloys: Werkzeugen und Werkzeugmaschinen Hartmetall CDA‘s Universal Machinability Index, [Determination of forces and capacities [The face character while machining of SAE International, Dokumenten on machining tools] hard metal] Nummer: 900365; Februar 1990 Z.VDI 94 (1952) S.299-305 VEB-Verlag Technik, Berlin 1953

[2] [11] [18] www.kupferinstitut.de N.N.: A Metal Cutting Investigation of Burmester und Burmester: Maßgebli- Silver-Bearing VS. Silver-Free- Copper, che Einflussgrößen beim Drehen von [3] Copper Range Company: New York 1964. Flächen mit kleinen Rautiefewerten www.wieland.de [Relevant factors at turning faces with [12] small peak-to-valley roughness] [4] Ausschuss für wirtschaftliche Fertigung: Maschinenmarkt 86 (1980) Nr. 60, König, W. und Essel, K.: Spezifische “Arbeitsergebnisse – AWF-Betriebsblatt S. 1163 ff Schnittkraftwerte für die Zerspanung 158” [Committee for economic fabri- metallischer Werkstoffe cation: „Work results – AWF working [19] [Specific cutting force data for metallic paper 158”] Kluft, W., König, W., Luttervelt, materials] Beuth-Verlag, Berlin, C. A. van, Nakayama, K., Pekelharing, Verlag Stahleisen M.B.H, A. J.: Present Knowledge of Chip Düsseldorf: 1973 [13] Control. Annals of the Cirp 28 (1979) 2, Sadowy, M.: Untersuchungen zur Theo- S. 441/455. [5] rie der Fließspanbildung. III Schnitt- Fleming, M.: Werkzeugkonzepte für das kräfte, Spanformen und Spanstauchung [20] Drehen von Getrieben mit PCBN (Fortsetzung) N.N.: Ecobrass Stangen – Drähte – [Tool concepts for turning of gears with [Research into the theory of continuous Profile – Rohre PCBN] Industrial Diamond Review 39 chip formation III Cutting forces, chip [Ecobrass Rods – Wires – Sections – (2005) Nr. I, S.23/28 forms and compressions (Continuance) Tubes] Maschinenmarkt 73 (1967) 10, S. 167-174 Firmenschrift der Wieland-Werke AG, [6] Ulm, 2006 Warnecke, G.: Spanbildung bei metal- [14] lischen Werkstoffen Philipp, H.: Über Messungen der spe- [21] [Chip formation of metallic materials] zifischen Schnittkräfte beim Walzen- Klocke, F.; König, W.: Fertigungsver- München: Technischer Verlag. fräsen fahren 1 – Drehen, Fräsen, Bohren Resch: 1974 [Measurements of the specific cutting [Production process 1 – Turning, forces while roll milling] milling, drilling] [7] Werkstatt und Betrieb 92 (1959) 4, Aufl.8, Springer, Berlin: 2008 Vieregge, G.: Zerspanung der Eisen- S.179-187 werkstoffe [22] [Machining of iron materials] [15] N.N.: Messingzerspanung mit PKD Band 16 der Stahl-Eisenbücher Verlag König, W. und Erinski, D.: Unter- [Machining of brass with PKD] Stahleisen Düsseldorf: 1970, 2.Aufl. suchungen der Zerspanbarkeit von Diamond Buisiness 34 (2008) 3, S. 34/35 Kupfer-Gusslegierungen [8] [Examination of the machinability of [23] Victor, H. und Zeile, H.: Zerspanungs- copper cast alloys] Dawihl und Dinglinger: Handbuch der untersuchungen und Schnittkraft- Forschungsvorhaben AIF-Nr. 4572 Hartmetallwerkzeuge messungen an Kupferwerkstoffen Laboratorium für Werkzeugmaschinen [Handbook of hard metal tools] [Research into machining and cutting und Betriebslehre der RWTH Aachen Bd.1. Berlin, Göttingen, force data of copper materials] (1982) Springer-Verlag, Heidelberg: 1953 wt-Z. ind. Fert. 62 (1972) 663-665 [16] [24] [9] Schallbroch, H.: Die Beurteilung der Krist, T.: Metallindustrie – Zerspan- Victor, H.: Schnittkraftberechnungen Zerspanbarkeit von Metallen technik – Verfahren, Werkzeuge, für das Abspanen von Metallen [Evaluation of the machinability of Einstelldaten [Calculations of cutting force data metals] [Metalindustry - Machining technique for metals] Z. VDI 77 (1933) 965-971 – Process, tools, setting data] wt-Z. ind. Fert. 59 (1969) 317-327 Hoppenstedt Technik Tabellen Verlag Darmstadt: 1993, 22. Auflage

DKI Monograph i.18 | 61 [25] [32] Paulo Davim, J.; Sreejith, P. S.; Brecher, C. (Hrsg.); Niehaus, F.; Silva, J.: Turning of Brasses Using et al.: Machine and Process Develop- Minimum Quantity of Lubricant (MQL) ment for the Robust Machining of and Flooded Lubrican Conditions. Microstructures on Free-Form Surfaces Materials and Manufacturing Processes, for Hybrid Optics. 22, 2007, S. 45–50 Apprimus Aachen, 2009, ISBN 978-3-940565-79-2 [26] Witthoff, J. Die Ermittlung der günstigsten Arbeitsbedingungen bei der spanabhebenden Formung [Determination of most effective working conditions for metal cutting techniques] Werkstatt und Betrieb 85 (1952) H. 10, S. 521 ff

[27] Voss: Optimierung spanender Fertigung [Optimizing of machining processes] Technischer Verlag Resch KG, Gräfelfing: 1976

[28] Burmester und Burmester: Schnitt- datenoptimierung an simultan spanenden Werkzeug-Kollektiven [Cutting data optimizing of simultaneously machining tools] Technisches Zentralblatt für Metall- bearbeitung, 1981

[29] Spenrath, N. M.: Technologische Aspekte zum Feinstdrehen von Kupferspiegeln [Technological aspects of micro-turning of copper reflectors] Dissertation RWTH Aachen, 1991

[30] Linke, B.: Wirkmechanismen beim Abrichten von keramisch gebundenen Schleifscheiben [MOA of true running vitrified bonded grinding wheels] Dissertation RWTH Aachen: 2007

[31] Riemer, O.: Trennmechanismen und Oberflächenfeingestalt bei der Mikrozerspanung kristalliner und amorpher Werkstoffe [Separation mechanism and surface finish of micro precision machining of crystalline and amorphous materials] Dissertation Universität Bremen, 2001

62 | DKI Monograph i.18 14 Standards, regulations and guidelines

DIN 1414-1/2 DIN 6581 DIN 1837 Technische Lieferbedingungen für Begriffe der Zerspantechnik; Bezugs- Werkzeug Anwendungsgruppe zum Spiralbohrer aus Schnellarbeitsstahl – systeme und Winkel am Schneidteil des Zerspanen, [Groups of tool application Teil 1: Anforderungen. [Technical Werkzeuges, [Terminology of chip re- for chip removal.] specifications for twist drills of high- moving; reference systems and angles Beuth Verlag, Berlin speed steel - Part 1: Requirements.] on the cutting part of the tool.] Beuth-Verlag, Berlin Beuth Verlag, Berlin ASTM E618 Standard Test DIN 343 DIN 6583 Method for Evaluating Machining Aufbohrer (Spiralsenker) mit Morse-ke- Begriffe der Zerspantechnik; Stand- Performance of Ferrous Metals Using gelschaft. [Core drills with morse taper begriffe, [Terms of cutting procedures; an Automatic Screw/Bar Machine, shank.] Beuth-Verlag, Berlin. tool life criteria.] Beuth Verlag, Berlin ASTM, 2007

DIN 344 DIN 6584 TrinkwV 2001 Aufbohrer (Spiralsenker) mit Zylinder- Begriffe der Zerspantechnik; Kräfte, Verordnung über die Qualität schaft, [Core drills with parallel shank.] Energie, Arbeit, Leistungen, [Terms von Wasser für den menschlichen Beuth-Verlag, Berlin. of cutting procedures; forces, energy, Gebrauch work, power.] Beuth Verlag, Berlin DIN 222 Directive 2002/95/EC Aufsteck-Aufbohrer (Aufsteck-Senker), DIN ISO 513 of the European Parliament and of [Shell drills.] Beuth-Verlag, Berlin. Klassifizierung und Anwendung von the Council of 27 January 2003 on harten Schneidstoffen für die Bezeich- the restriction of the use of certain DIN 8022 nung der Hauptgruppen und Anwen- hazardous substances in electrical and Aufsteck-Aufbohrer (Aufsteck-Senker) dungsgruppen Metallzerspanung mit electronic equipment. – ROHS -Official mit Schneidplatten aus Hartmetall. geometrisch bestimmten Schneiden Journal L 037 , 13/02/2003 P. 0019 – 0023 [Shell core drills with hard metal tips.] [Classification and application of hard Beuth-Verlag, Berlin cutting materials for metal removal Directive 2000/53/EC with defined cutting edges – Designa- of the European Parliament and of the DIN 8043 tion of the main groups and groups of Council of 18 September 2000 on end- Aufbohrer mit Schneidplatten aus application] of life vehicles. –ELV- Official Journal Hartmetall. [Core drills with carbide L 269 , 21/10/2000 P. 0034 – 0043 tips.] Beuth-Verlag, Berlin. DIN EN ISO 4957 Werkzeugstähle, [Tool steels.] VDI Richtlinie 3321 CEN/TS 13388 Beuth Verlag, Berlin Blatt 1: Optimierung des Spanens – Kupfer und Kupferlegierungen Über- Grundlagen. sicht über Zusammensetzungen und DIN EN ISO 4287 VDI-Verlag GmbH Düsseldorf Produkte, [Copper and copper alloys Geometrische Produktspezifikation – Compendium of compositions and (GPS) – Oberflächenbeschaffenheit: products.] Berlin: Beuth Verlag Tastschnittverfahren – Benennungen, Definitionen und Kenngrößen der DIN EN 1982 Oberflächenbeschaffenheit, [Geo- Kupfer und Kupferlegierungen - Block- metrical Product Specifications (GPS) metalle und Gussstücke, [Copper and – Surface texture: Profile method – copper alloys – Ingots and castings.] Terms, defi-nitions and surface texture Berlin: Beuth Verlag parameters.] Beuth Verlag, Berlin DIN 6580 Begriffe der Zerspantechnik; Bewegun- gen und Geometrie des Zerspanvor- ganges, [Terminology of chip removing; movements and geometry of the chip removing process.] Beuth Verlag, Berlin

DKI Monograph i.18 | 63 64 | DKI Monograph i.18

Auskunfts- und Beratungsstelle für die Verwendung von Kupfer und Kupferlegierungen

Am Bonneshof 5 40474 Düsseldorf Telefon: (0211) 4 79 63 00 Telefax: (0211) 4 79 63 10 [email protected] www.kupferinstitut.de