Presentation on theme: "Authored by: P T Mativenga & K K B Hon"— Presentation transcript:
1Authored by: P T Mativenga & K K B Hon A Study of Cutting Forces and Surface Finish in High-Speed Machining of AISI H13 Tool Steel Using Carbide Tools With TiAIN Based CoatingAuthored by: P T Mativenga & K K B HonPresented by: Ted HandOctober 27, 2004
2Introduction Purpose of the paper: “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.
3Background 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 ratesCoatings are expected to result in lower wear regions occurring at higher spindle speeds, promoting the use of HSM.
4Surface RoughnessDefinition: 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 diameterSz = Vf / Nt N = chip loadNt = number of edges that advance in a revolution of the cutterN = spindle speed in r/minVf = feed rate
5Parameters Machine tool: Cutting tools: Mikron HSM 700 42000 r/min12 kw spindle capable of a 20m/min cutting feed and 40 m/min rapid feedCutting tools:6mm ball-nose end millsPVD coatedMicrograin alloy WC 10% Co
6Table 1: Geometrical properties of the ball-nose end mill used in the experiments Tool parametersSymbolValueNumber of flutes2°°Helix angleλ30°Rake angleγ0°Shank diameterd6mmOverall tool lengthlt57mmNominal length below chucklnorm20mmCut lengthlc7mmCutter diameterCorner Radiusr3mmSetting angleχ
7Table 2: Properties of PVD coatings Coating materialTiNTiCNCrN2TiAlNTiAlNTiAlN + WC/CMicrohardness (HV 0.052300300017503500Coefficient of friction against steel (dry)0.40.50.2Coating thickness (μm)1--41--51--32--6Maximum working temperature (°C)600400700800
8Cont. Work material: Finishing operations use the following coatings: Mid range hot work tool steel AISI H13Finishing operations use the following coatings:TiNTiCNCrNTiAlN2TiAlNTiAlN + WC/CThree components of the cutting forces were sampled and averaged.
9Milling StrategyTable 3: Cutting parameters for AISI H13 tool steel HSM experimentsTool diameterD6mmDepth of cuta.06mmWidth of cutbRapid feedVf-rapid10,000 mm/minRamp feedVf-ramp500 mm/minCutting feedVf6000 mm/minDirection of linear interpolationx axisDirection of tool step-overy axis
10EvaluationSurface finish was evaluated using a Mitutoyo SURFTEST 301 with a cut-off value of .8mm and a span of .5mm25 measurements takenSurface integrity studied with a optical microscope and an SEM
11ResultsTable 4: Correlation coefficients of surface finish to cutting forcesStep-over directionG01 directionFxFyFzPeak FzTiN0.830.841.000.990.810.98TiCN-0.140.90-0.200.870.960.95CrN0.930.620.970.890.590.94TiAlN0.420.490.880.440.310.73Uncoated0.740.710.500.572TiAlN-0.090.80TiAlN + WC/C-0.030.190.350.38-0.30-0.21-0.05
12GraphsFigures 2-10How the surface finished is affected by the spindle speed.
13Cont.HSM with TiCN, TiN, CrN, single and double layered TiAlN produced a better surface finishTiAlN gave the best results, but need to minimize interaction with steelCrN didn’t present an advantage
14ConclusionsPVD tool coatings improved the surface finish compared to uncoated toolsCoatings had the smallest wear zone promoting higher cutting speedsHigher cutting speeds and PVD coatings are pushing the frontiers in surface finishing's.
15Implications Reducing die making lead times Cutting costs with smaller lead timesIndustries affected:AerospacePrecision machine labsAuto industryEtc.
16References:Edwards, R. Cutting Tools, 1993, pp (The institute of Materials)ISO 368 Surface Roughness—Parameters, Their Values and General Rules for Specifying RequirementsLim, S.C. and Lim, C.Y.H. Effective use of coated tools—the least wear map approach. Surface and Coatings Technol., 2001, 139,Konig, W., Komanduri, R., Tonshoff, H.K. and Ackershott, G. Machining of hard materials—Key Note papers. Ann. CIRP, 1984, 33(2),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),