CAM02 - Planar Cutting

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1、ManufacturingProcessesMaterialRemoval(PlanarCutting)CuttingMethods•CuttingTools–SinglePoint–StraightEdge–ObliqueEdge•Abrasive–Grinding–Lapping–Polishing•NonTraditional–ElectroDischargeMachining(EDM)–Laser–ChemicalMilling21ReasonsforCutting•AchieveCloserDimensions•

2、CreateDifficultGeometries•FinishingOperations•SpecialFinishes•CreatingSmallNumbersofParts3ProblemswithCutting•Scrap•Speed•SurfaceQuality(Sometimes)42CuttingParameters•ToolMaterial•ToolCondition•ToolShape•WorkPieceMaterial•WorkPieceCondition•CuttingConditions(Feed,

3、Speed,Depth)•MachineCondition5DependentParameters•TypeofChip•ForceandEnergyofCut•Temperature•ToolWear•SurfaceFinish63CuttingTerminology•ChipThickness,tc•DepthofCut,toandtc>to•RakeAngle,α•ShearAngle,φto•CuttingRatio,rr=tc•Compressionratio,1/rsinφ=cos(φ−α)7CuttingGe

4、ometryRakeAngle–+ChipαVtcToolShearRelieftoφAngleAngleWorkpieceShearPlane84CuttingRatioAnalysistosinφto=AB=tcos(φ−α)tcsinφctc=cos(φ−α)αChip90–αToolB90–φtoφAWorkpieceφ–α9VelocityAnalysisSincevolumeisconservedandVVVcstc>tothenVc

5、VcαV=Vccos(φ−α)ChipToolVBtoφAWorkpiece105VelocityDiagram90o–φ+αVVVVcsc==Vcos(φ−α)sinφcosαsαφ–α90o–αφV11TypesofChipsI•ContinuousChips–Formedbyhighcuttingspeedsand/orrakeangle–Goodsurfacefinishassociatedwiththesechips–Deformationalonganarrowshearzone–Lowspeedsandsof

6、tmaterialsproduceawideshearzone•Shearzonemaydipbelowthecuttingplane•Poorsurfacefinishandresidualstressesresult–Chipscangetcaughtbetweentoolandworkpiece126TypesofChipsII•SerratedChips–Semi-continuous–Sawtoothappearance–Producedbecauseoflowthermalconductivity•Caused

7、byrapidlossofstrengthassociatedwithhightemperatures•Titaniumproducesserratedchips13TypesofChipsIII•DiscontinuousChips–Producedwhenthereisa•Brittleworkpiece•Veryloworhighspeed•Largedepthsofcut•Lowrakeangle•Lowmachinestiffness•Lackofcuttingfluid–Poorsurfaceresultssi

8、ncethemachinevibrates147ChipGeometryContinuousChipSerratedChipDiscontinuousChipSecondaryShearZonePrimaryShearZoneDeformedZoneBuilt-UpEdge15Built-UpEdge(