A Study of Cutting Forces and Surface Finish in High-Speed Machining of AISI H13 Tool Steel Using Carbide Tools With TiA

1. A Study of Cutting Forces and Surface Finish in High-Speed Machining of AISI H13 Tool Steel Using Carbide Tools With TiAIN Based Coating Authored by: P T Mativenga & K K B Hon Presented by: Ted Hand October 27, 2004

2. Introduction “Process improvement should not compromise but should enhance product quality.” Purpose of the paper: Address the effects of increasing machining speeds as well as the effects of different advanced coatings on surface finish.

3. Coatings TiC coatings Reduce cutting T, forces, and increase abrasion resistance as well as acting as a diffusion barrier. Expand the region of machining conditions which reduces wear rates Background Coatings are expected to result in lower wear regions occurring at higher spindle speeds, promoting the use of HSM.

4. Surface Roughness • Definition: relatively closely spaced or fine surface irregularities, mainly in the form of feed marks left by the cutting tool. • Surface roughness: Ra = S2z / (18 x (3(D/2 + SzNt/ pi)).5) • D = tool diameter • Sz = Vf / Nt N = chip load • Nt = number of edges that advance in a revolution of the cutter • N = spindle speed in r/min • Vf = feed rate

5. Parameters • Machine tool: • Mikron HSM 700 • 42000 r/min • 12 kw spindle capable of a 20m/min cutting feed and 40 m/min rapid feed • Cutting tools: • 6mm ball-nose end mills • PVD coated • Micrograin alloy WC 10% Co

8. Cont. • Work material: • Mid range hot work tool steel AISI H13 • Finishing operations use the following coatings: • TiN • TiCN • CrN • TiAlN • 2TiAlN • TiAlN + WC/C • Three components of the cutting forces were sampled and averaged.

9. Milling Strategy

10. Evaluation • Surface finish was evaluated using a Mitutoyo SURFTEST 301 with a cut-off value of .8mm and a span of .5mm • 25 measurements taken • Surface integrity studied with a optical microscope and an SEM

11. Results

12. Graphs • Figures 2-10 • How the surface finished is affected by the spindle speed.

13. Cont. • HSM with TiCN, TiN, CrN, single and double layered TiAlN produced a better surface finish • TiAlN gave the best results, but need to minimize interaction with steel • CrN didn’t present an advantage

14. Conclusions • PVD tool coatings improved the surface finish compared to uncoated tools • Coatings had the smallest wear zone promoting higher cutting speeds • Higher cutting speeds and PVD coatings are pushing the frontiers in surface finishing's.

15. Implications • Reducing die making lead times • Cutting costs with smaller lead times • Industries affected: • Aerospace • Precision machine labs • Auto industry • Etc.

16. References: • Edwards, R. Cutting Tools, 1993, pp.44-49 (The institute of Materials) • ISO 368 Surface Roughness—Parameters, Their Values and General Rules for Specifying Requirements • Lim, S.C. and Lim, C.Y.H. Effective use of coated tools—the least wear map approach. Surface and Coatings Technol., 2001, 139, 127-134. • Konig, W., Komanduri, R., Tonshoff, H.K. and Ackershott, G. Machining of hard materials—Key Note papers. Ann. CIRP, 1984, 33(2), 417-427. • DeVries, W.R. Analysis of Material Removal Processes, 1992, p.138 (Springer - Verlag, Berlin). • Da Silva, M.B. and Wallbank, J. Lubrication and application method in machining. Ind. Lubric. Technol., 1998, 50(4), 149-152