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2021/4/16SCUT13.6Themethodtoclamptheworkpieceandobtainthedesiredaccuracy3.6.1Theclamping(1)Positioningandclampingbydirectlocation(直接找正定位）Whenputtingtheworkpiecedirectlyonthemachinebed,theoperatorcanlocatethemachinedsurfacebyusingamicrometer（千分尺）inspectinginstrument（测量仪）,markingdish（划线盘）orstraightrulestoadjustandfindthedesiredmachiningpositionrelativetothecuttingtool.Itisusuallyusedinsingleorsmallbatchtypeproduction,orintheconditionofhighaccuracymachiningrequirementtorelativepositionwhenitishardtomeetbyafixture.Fig.3-6-1setupbylocatingmovie2021/4/16SCUT2（2）Clampingaccordingtothepre-markedtrailoftheoutline（划线找正装夹）Thiskindofclampingmethodiswidelyusedinsingleorsmallbatchtypeproduction，andtheerroroftheoperationitselfexists,theclampingaccuracyislow,usuallyintherange0.2～0.5mm.Beforetheworkismachined,theoutlineofthesurfacetobemachinedontherawmaterialismarked,thenlocatedandclampedonthemachinetoolaccordingtothepre-drawnlines.Whenusingthismethod,sufficientmetalremovalmustbeensured.3.6Themethodtoclamptheworkpieceandobtainthedesiredaccuracy2021/4/16SCUT3(3)Clampedwithafixture（夹具）Thiskindofmethodisconvenient,fast,preciseandstable.Itiswidelyusedinbatchtypeproductionandlargequantityproduction.Forexample,inFig.4-1,itisanoperationofmachiningakeyinasteppedshaft.Forsomepartsinsmallbatches,suchastheconnectingrodorcrankshafts,eventhoughthebatchquantityisnotlarge,somespecialfixturesarestillrequiredinordertomeetthespecificmachiningrequirement.3.6Themethodtoclamptheworkpieceandobtainthedesiredaccuracy2021/4/16SCUT4Fig3-6-2thesetupofthekeywaymachinedbymillingObviously,therelativepositionalaccuracyamongdifferentsurfacesinmechanicalmachining,suchasparallel,theperpendicularandcoaxialdegreesofaccuracy,canbeobtainedwiththeaboveclampingmethodusingseveralclampingsteps,andalsoitcanbeobtainedbyarrangingthedifferentsurfacestobemachinedinthesameclamping.Thesetwomethodsarebothcommonlyusedtoobtaintherelativepositionalaccuracyinmechanicalmachining.feedclampingclamping3D2021/4/16SCUT5（1）Methodsofobtainthedimensionalaccuracyinmechanicalmachining①Trialcuttingmethod②Settingdimensionmethod③Adjustmethod④AutomaticcontrolmethodAtinypartofthesurfacetobemachinedispre-cut,andthedimensionsareinspected.Then,properadjustmentismadeaccordingtothedesiredrequirement,andtrycuttingistriedagain.Theaccuracyofthemachinedsurfaceisensuredbyapplyingacuttingtoolwiththerequiredaccuracy,suchasareamer,twistdrillorcoredrill.Theaccuracyisensuredbythecuttingroutesettingdeviceorpre-adjustedcarriages1）Automaticinspection—theinspectiondeviceisintegratedintothemachinetool.Whenthedimensionsaresatisfied,aninstructionwillbesentfromtheautomaticinspectiondevicetomakethecuttingtoolrecedeorstop.2）Numericalcontrol—asteppingmotor,rollingscreworawholenumericalcontrolleddeviceisusedtocontrolthemovementofcuttingtoolorworktableprecisely.Thedimensionsareachievedbypre-programmedinstructionstocontrolthemovementofcarriagesorworktablethroughacomputercontrollednumericaldevice.3.6.2Methodsofobtainingtheaccuracyofthedimension2021/4/16SCUT6（2）Methodstoobtainthedesiredgeometricalshapebymechanicalmachining①pathmethod③Formingmethod(4)Generatingmethodthegeometricalshapeofthepartisformedbythemovementofthecuttingtooltip.Theaccuracyofthismethodismainlydependentontheaccuracyofthecutter’smovement.theshapeoftheworkpieceisformedbysynthesisoftwomovements,oneofwhichisthemovementofthecuttingtool,andanotheristhemovementoftheworkpiece.Thegeometricalshapeoftheworkpieceisanexactcounterpartofthecuttingtool.Theaccuracyofthismachiningmethodismainlydependedonthegeometricalaccuracyofthecuttingtoolanditsclampingaccuracy.（2）TangentialMachining（相切法）——Theedgemovesalongacertaintrackwhilerotating.3.6.3Methodsofobtainingtheaccuracyoftheshape2021/4/16SCUT72021/4/16SCUT83.6.3Methodsofobtainingtheaccuracyoftheshape