case study Super abrasive machining for PM Cost-effective secondary finish process offers upstream cost savings for manufacturers of aerospace, automotive, and industrial components. n today’s fast-paced world, how often ny’s stock removal processes has been • Wheel feed rate do you hear the phrase, “We wel- proven to save its users money by replac- • Coolant make-up, flow and applica- come interruptions?” Super abrasive ing traditional grinding or single-point tion (presentation) machining (SAM) does just that. machining applications. • Machine action, platform and capa- IThe impact of this secondary proc- It’s important to distinguish the dif- bility. ess is having a dramatic effect on the ferences between grinding and SAM. reliability and cost associated with dif- Although both are performed with ficult interrupted and other heavy and a wheel and not a single point tool, The correct complex cuts. These types of component grinding is typically used to remove applications geometries, whose numbers are ever a small amount of stock material to increasing with the growth and increas- achieve a final size and finish. SAM, by Because of the higher capital, wheel ing complexity of VVT (variable valve tim- comparison, is used to machine parts and fixturing costs associated with SAM ing) chain and gear drives (see Figure 5), from differing geometries and features when applied to net shape processes, besides the expanding demand of PM to extremely high degrees of accuracy users of the technology look for rapid to combine multiple components into and surface finish. Another distinction: paybacks of this initial investment. In single pressings, once threatened the SAM equipment more closely resembles order to improve this rate of payback, it economics of PM to satisfy these needs. horizontal milling machines than surface is important to properly choose the cor- Given the speed, accuracy and stock grinders. Of course, that’s rather appro- rect applications for the process. SAM removal capabilities of SAM, not only can priate because they produce parts at should be used not as a replacement the cost targets for component manufac- near machining speeds. for single point machining or conven- ture be achieved, but the complexity and Let’s look at the actual processing, tional grinding, but as a supplement for function of the component can also be choosing creep fatigue grinding (SAM’s applications where other, more readily improved for the same price. closest rival) as a mode of comparison. available processes are commonly mis- SAM is a process for difficult and While both processes remove substantial specified. substantial material removal or “cut- amounts of material and finish to close Prime examples of these niche type ting” operations. Commonly referred to tolerances, SAM achieves the equivalent applications are as follows: as “grinding at machining rates,” SAM at higher speeds, faster material remov- 1) Multiple-step process such as mill- offers the precision of grinding at speeds al rates and at lower workpiece loads, ing, heat treating and then grinding can and costs similar to those generated by producing better dimensional capabili- be replaced with a single operation. The single point machining. Once exclusively ties and reducing the risk of component entire manufacturing process is simpli- a tool making/sharpening and aerospace damage during deformation. The nonex- fied and more controllable. component machining technology, its istent or minimal remaining burr or sharp 2) PM gears and sprockets with inter- application has recently been expanded edge remaining usually requires reduced rupted cuts (see Figure 6). They are to a wide variety of machine styles and deburring – or none at all. Depending on capabilities. It may now be possible to the magnitude of these machining burrs, expand this capability outside its tradi- the cost of their removal can, at times, tional markets into large-scale automo- rival the cost of the parent machining tive and industrial component manufac- process itself. turing. In this arena, the cost-effective Successful SAM involves the integra- implementation of SAM can reverse the tion and improvement of these material, cost-driven pressures on these indus- equipment and processing factors: tries. This mix of trade secrets, talents • Wheel design, geometry, material and Figure 1: Automotive Drive and techniques in a particular compa- speed Gear – From Machine – HT – Grind to HT-SAM 38 MPR November/December 2012 0026-0657/12 ©2012 Elsevier Ltd. All rights reserved www.sms-meer.com/ecoplants SUSTAINABLE OR PROFITABLE? IT’S AND, NOT OR. Ecoplants is the new mark for sustainable Quality unites – a fact that our customers solutions by SMS Meer, designed to give and we discover time and again with our customers economic and ecological every new project. Together we develop advantages in the market. Economic solutions that give our partners the because saving energy and raw materials competitive edge in their business. Thanks reduces costs, and eco logical because to this good cooperation, SMS Meer is a protecting resources is becoming in- leading international company in heavy creasingly important. Ecoplants solutions machinery and plant engineering. by SMS Meer do both – for the benefi t of our customers. www.sms-meer.com SMS_AZ_EcoPlants_A4_WireCable.indd 1 16.07.12 11:04 Figure 2: Pawl Holder – Slot cre- Figure 3: Auto idler sprocket. Figure 4: Multi-lever assembled camshaft sprocket formed in single ated by SAM. level press SFH-SAM. is an important factor in the efficiency of the SAM process. The rotating action of an interrupted cut (i.e. sprocket or gear teeth) forms a “paddle” action that drives additional coolant to the machin- ing interface. This effect increases the efficiency of the cutting operation and – when combined with the inherent wheel, fixturing and machine platform construc- Figure 5: Automotive VVT sprocket – from Figure 6: Multi-level assembled camshaft 2pc sinter braze/INT HT/machine to 1PC. sprocket formed in single-level press SFH- tion advantages – produces a better rate –SFH-SAM SAM. and resulting higher quality part with substantially lower tool cost than the equally as effective on heat treated or simply comparing the costs of specific single point machining option. SFH materials where single point turn- SAM and alternative machining/grind- Figure 7 quantifies this advantage by ing is not. By maximizing the use of PM ing operations. Table 1 identifies the comparing the wheel life/cost of a solid and other net shape processes, SAM is upstream and downstream process cost cut (depth = 10.16 mm) with an inter- very effective in combining geometries reduction of a properly placed SAM oper- rupted cut of the same depth at a wheel and converting multiple pieces into one ation. This could increase when making speed of similar surface feet per minute piece construction. This involves full a component with an appropriate geom- (SFPM) in value. utilization of single-action PM pressing etry whose compaction design is cor- capacity by combining the lower burden rectly influenced by SAM capabilities. cost of this equipment with SAM to pro- Heat treated duce features typically pressed by more interrupted cuts expensive compacting equipment. Why SAM welcomes 3) Flats, straight side walls and formed interruptions The creation of a heat-treated interrupted slots (see Figure 2) . cut has been a longstanding holy grail of While interrupted cuts can have a negative PM manufacturing. SAM not only makes impact on single point turning machining this possible, but also, as depicted in PM cost improvement operations, an interrupted cut can actu- Figure 8, within a cost structure compa- Because SAM can involve substantial ally enhance the cutting/machine rate rable to its application on sintered com- stock removal at economic rates, cost in SAM. As previously mentioned, cool- ponents and far superior in performance justifications need to go further than ant delivery to the wheel/part interface and quality to the single point turning alternative. Table 1: Upstream and downstream PM process cost reductions driven by SAM. Simpler tool designs Reduced HT distortion Further development More robust tools Lower cost compaction capital SAM represents a virtually untapped Less complex components Reduced in process measurement time process technology that greatly enhanc- es PM’s ability to further its offering of Lower tool maintenance Reduced crack checking complex and cost-effective components. Lower set up times Improved quality costs – process stability Properly designed, specified and Less tool sets Reduced gauging costs built SAM systems (wheel, cutting fluid, Lower set up scrap Elimination of post machining distortion platform rigidity, speed) combined with Higher compaction rates Expanded application reach custom engineered full process appli- cations offer cost-effective and highly Higher compaction process yields Elimination of deburring costs efficient stock removal capabilities that Reduced sintering distortion Expanded compaction utilisation greatly enhance the net shape advan- possibilities tages of PM. This is achieved by making 40 MPR November/December 2012 metal-powder.net Figure 7. SAM wheel cost comparing solid vs. interrupted cut. Figure 8. Cutting tool cost: SAM vs. single point turning. it possible to create additional geometric to the inherent machinibility structure, have traditionally been used, sometimes features that otherwise cannot be com- thereby eliminating the added costs of mistakenly, to service such needs. pacted, or whose costs and resulting additives and resin impregnation. This unreliability of their compacting make additive/process elimination also goes the entire PM option uncompetitive. against the decrease in material strength About the author SAM represents a process technology caused by the introduction of these pur- that will work to continue to extend the poseful material inconsistencies. Rocco Petrilli is the founder, presi- application of PM and other net-shape As well as this, the process can be a dent and managing partner for Super processes deeper into its traditional and more cost-effective and reliable replace- Abrasive Machining Innovations, new markets.