1 Ivan Sovilj-Nikić, Phd Student, FTN, Trg Dositeja Obradovića 6 and

34th INTERNATIONAL CONFERENCE ON PRODUCTION ENGINEERING 28. - 30. September 2011, Niš, Serbia University of Niš, Faculty of Mechanical Engineering

INFLUENCE OF WEAR OF CUTTING ELEMENTS OF CONVEX MILLING CUTTERS ON PROCESSED SURFACE TOPOGRAPHY

Ivan Sovilj-Nikić, Bogdan Sovilj, Stanislaw Legutko, Sandra Sovilj-Nikić, Ivan Samardžić, Ivan Kolev Faculty of technical science, University of Novi Sad, Trg Dositeja Obradovića 6, Novi Sad, Serbia [email protected], [email protected], [email protected] [email protected],[email protected], [email protected]

Abstract: The actual area of contact is the basic size and starting point for investigation and interpretation of tribological processes, and its determination is one of the primary tasks of research. This paper presents the results of experimental research on the impact of wear of cutting elements of convex milling cutter on the processed surface topography.

Key words: cutting element, convex milling cutter, wear, cutting speed, feed, processed surface topography roughness of contact surfaces is very important. To 1. INTRODUCTION complete the picture of contact surface topography is necessary to define the roughness precisely. Based on a In the process of cutting contact of convex milling cutter complex research of milling process, in this paper a part with a workpiece material is achieved between scraped of the research results related to the processing of surfaces and face area, as well as between back surface of the using convex milling cutter is given. cutting element and processedsurface[2,3,4]. Tribological processes that occur in the process of cutting 2. BASIC OPERATIONS OF PROCESS OF on both surfaces of the tool cutting element are developed MILLING PROCESSING under specific conditions. Research of wear process of convex milling cutter on characteristics of the state and Modern milling is a very universal machining method. output effects of machining process is very important. During the past few years, hand-in-hand with machine Quantifying the actual contact area is linked with a tool developments, milling has evolved into a method that number of unresolved issues when it comes from machines a very broad range of configurations. methodology and instrumentation. Production operations of milling cutter processing are One of the future procedures for determining the actual classified according to type and shape of milling used for area of contact is based on its topography. Due to the processing into: facing cutter milling, end-milling cutter existence of a higher order surface roughness and the milling, side and face cutter milling etc (fig.1) [5,7,9]. existence and development of tribological processes in this area, it is necessary to improve methodologies that An effective usage of working means in metal industry define the topography. demands knowledge of current parameter process. The Topography parameters of contact surfaces of elements of technological parameters which influence tool wear take tribo-mechanical systems are result of previous and final an important place in the process. Together with operations of machining process[1,6,8]. parameters for determination of process economy they The geometrical parameters of contact surfaces are effect the realization of optimal parameter of cutting significantly changed under the influence of plastic regime. deformation, the efforts by other structures and destruction of the structure by friction. Starting Important precondition for the process economy is the topography, caused by processing technology, is possession of actual cutting information. The need for this continuously changed during the cycle of exploitation. information is growing with increased application of The contact surface of tribo-elements, after finish computer in the process control and automated systems. processing, is never absolutely smooth. Numerous The number of data is larger at milling due to process irregularities resulting from previous and final operations complexity and due to variety of milling possibility. may have different geometric parameters and induce more Insight into the milling process is more complicated due or less irregularities of tribo-elements. to following facts: Characteristic parameters, inherited during the  tool is periodically in the contact with the technological process, define macro and micro geometry material of contact areas. For the correct analysis of tribological  changeable number of cutters in contact with processes and tribologically correct construction, material  changeable component width 3. RESEARCH RESULTS  possible changes of input and output angle due to different relation between tool and workpiece. Milling process is, in comparison to the other working processes, a specific one. During milling process not only one tooth takes part in the process but as many teeth as the tool has it. Radius of every tooth can vary and this can influence the process in significant way. It means that some of the teeth will be involved much more in the process. The cutting load at those teeth is also much higher, the milling process is more intensive. Therefore, the radial eccentricity has been measured at milling tools which are in assembly with the machine, i.e. radial eccentricity relative to rotation axe and not relative to milling tool axe. Investigations were realized in real conditions as follows: a) working piece: material 1C45, improved, chemical composition(table), dimensions 475x250x65

Table 1. Chemical composition of the working piece C(%) Si(%) Mn(%) P(%) S(%) 0.50 0.35 0.80 0.045 0.045

b) tool: convex milling cutters f63 , material HS6- 5-2-5, tooth number z=12

c) machine: universal milling machine GU-2

Measuring of wearing zone width was realized at tool Fig.1. The main types of milling operations microscope ZEISS. Research was consisted of development of wear process at various cutting speeds Observing of surface quality at the workpiece has been and feeds. performed by means of roughness parameters ( Rmax , RZ , Table 1 shows conditions of experiment realization and figures 2-8 shows measured values of parameters of Ra , Rs , Rt , R3z max , R3z )in dependence of cutting length roughness. (L).

Table 1. Conditions of experiment realization Experiment – tool Machine Tool Working piece tag GU-2 Convex milling cutter 1C45 23HRC 063(R5) HS6-5-2-5 No. of Radial Milling No. of milling Cutting Feed rotations runout procedure cutters depth (mm) (mm/min) (rot/min) (mm) I-G1 5 125 100 0.10 Opp. direc. 1 II- G2 5 125 160 0.15 Opp. direc. 2 III-G3 5 200 160 0.08 Opp. direc. 3 IVG4 5 200 100 0.20 Opp. direc. 4 V-G5 5 160 125 0.12 Opp. direc. 5 VI-G6 5 160 125 0.16 Opp. direc. 6 VII-G7 5 160 125 0.12 Opp. direc. 7

1 Ivan Sovilj-Nikić, PhD student, FTN, Trg Dositeja obradovića 6 and [email protected]. 2 Bogdan Sovilj, Prof. dr, FTN, Trg Dositeja obradovića 6 and bsovilj. 3 Stanislaw Legutko, Prof. dr hab, Politechnika Poznanska, Piotrowo 3. and [email protected]. 4.Sandra Sovilj-Nikić, PhD student, FTN, Trg Dositeja obradovića 6 and [email protected]. 5.Ivan Samardžić, Prof. dr, Mechanical Engineering Faculty. Trg Ivane Brlić Mažuranić 2 and Ivan [email protected] 6.Ivan Kolev, Assoc.Prof, "Angel Kanchev" University of Ruse, R&DS, Studentska 8. and [email protected]  with speed increase milling cutter life decreases for 30-40 % the smallest milling cutter life was obtained for mean values of speed and feed (experiments V-VII) Analyzing the diagrams on figures 2-8, it can be concluded that wear parameters, almost for all tools, increase in the beginning of processing and afterwards they decrease. Also, the tool lives are different for different processing regimes.

Fig.2. Dependence of wear parameters on length of cutting by tool G1

Fig.5. Dependence of wear parameters on length of cutting by tool G4

Fig.3. Dependence of wear parameters on length of cutting by tool G2

Fig.6. Dependence of wear parameters on length of cutting by tool G5

Fig.4. Dependence of wear parameters on length of cutting by tool G3

Based upon investigation results from experiment I and IV; and II and III it can be concluded:  at constant cutting speed and with feed increase, milling cutter life significantly decreases at constant feed

1 Ivan Sovilj-Nikić, PhD student, FTN, Trg Dositeja obradovića 6 and [email protected]. 2 Bogdan Sovilj, Prof. dr, FTN, Trg Dositeja obradovića 6 and bsovilj. 3 Stanislaw Legutko, Prof. dr hab, Politechnika Poznanska, Piotrowo 3. and [email protected]. 4.Sandra Sovilj-Nikić, PhD student, FTN, Trg Dositeja obradovića 6 and [email protected]. 5.Ivan Samardžić, Prof. dr, Mechanical Engineering Faculty. Trg Ivane Brlić Mažuranić 2 and Ivan [email protected] 6.Ivan Kolev, Assoc.Prof, "Angel Kanchev" University of Ruse, R&DS, Studentska 8. and [email protected] Fig.7. Dependence of wear parameters on length of edges and topography parameters allows determination of cutting by tool G6 the tooth wear criteria of convex milling cutters.

REFERENCES

[1] IVKOVIĆ, B., RAC, A. (1995) Tribologiija, Jugoslovensko društvo za tribologiju [2] SOVILJ, B. (1988) Identifikacija triboloških procesa pri odvalnom glodanju, Univrezitet u Novom Sadu [3] KOLEV, I. (2009) Rjazane na materialite, RU “Angel Kincev” [4] DUDAS, I. (2003) Gepgyartas-teccnologia III, Miskolci egytemy kiado [5] NESLUSIN, M., et all (2007) Experimentalne metody v trieskovom obrabani, Zilinska univerziteta v Ziline [6] TANASIJEVIĆ, S. (2004) Tribološki ispravno konstruisanje, Mašinski fakultet u Kragujevcu Fig.8. Dependence of wear parameters on length of [7] ČUŠ, F. (2009) Postopki odrezavanja, Univerza v cutting by tool G7 Mariboru [8] SOVILJ, B., et all (2010) Identification and methods of measuring tribological characteristics of materials, 4. CONCLUSION Scietific Journal of Agricultural Engineering, Vol. 36, No. 3, pp 295-304 Based on obtained research results it can be concluded [9] SANDVIK COROMANT (2005), Metalcutting that the wear of cutting elements of the convex milling technical guide, Sandvik Coromant cutter has a direct impact on the topography of processed surface. This relationship between the wear of tool cutting