机械制造技术基础课件-新第1章课件

Chapter1FundamentalsofMachiningAbstract1.1Basicdefinitions1.2MaterialsofcuttingtoolsMostofmetalpartsareshapedbymachiningatpresent.Machiningmeansthattheexcessmetalonablankiscutoffbyacuttingtool,thusformingitintoarequiredpart.Inthischapterwewillstudythefundamentalknowledgeconcerningmetalmachiningprocess.Therearetwoparts:1.Basicdefinitions—cuttingmotionsandparameters,toolanglesandreferenceframe,cuttinglayerparametersetc.2.Cuttingtoolmaterials—thenecessaryproperties,somenormalcuttingtoolmaterials.Absract1.1Basicdefinition1.1.2Basicdefinitionsofcuttingtool’workingregion1.1.3Markedanglesofcuttingtoolandtheirexchange1.1.5Cuttinglayerparametersandcuttingmode1.1.4Workinganglesofcuttingtool1.1.1CuttingmotionsandparametersMachiningincludessomedifferentprocessessuchasturning,drilling,milling,planingandbroachingetc.Butnomatterwhatmachiningprocess,itisainteractioncoursebetweenthecuttingtoolandtheworkpiece.1.1.1CuttingmotionsandparametersFig.1.1turningandmillingThereexistcommonrulesandphenomenon:Theworkpieceisholdeninmachinebyaclamper,soisthecuttingtool;Inordercarryingoutmachining,theremustbearelativemotionbetweentheworkpieceandcuttingtool,thatis,cuttingmotion,whichisprovidedbythemachine;Themachine,clamper,workpieceandcuttingtoolconstituteamachiningprocessingsystem.Comparingvariouscuttingtoolsusedindifferentprocesses,theyaresomepartssimilartoasimpleturningcutter.Then,takingturningasanexampletointroducethecuttingmotion.Inexternalcylinderturning,theworkpiecerotatesandthecuttingtoolmoveslongitudinally.Thetwomotionscomposetheexternalcylindricalsurface.Therearethreesurfacesintheworkpiece:Machinedsurface：meansthesurfaceinwhichthematerialhasbeenremoved.Fig1.2Cuttingmotionsinturning1.1.1CuttingmotionsandparametersSurfacetobemchinedworkpiecerotatesMachinedsurfaceSurfacebeingmachinedcuttermoveslongitudinallyMachiningsurface：meansthesurfacewhichisbeingmachinedbythecuttingedge.Surfacetobemachined：meansthesurfaceinwhichthematerialistoberemoved.Therearesimilarthreesurfacesinothermachiningprocesses:Fig1.3Cuttingmotionsinplaning,drillingandmilling1.1.1Cuttingmotionsandparameters1.CuttingmotionThebasicmotionforamachineincludeslinearmotionandrotationalmotion.Ifclassifiedaccordingtotheircuttingfunctions,theymaybedividedintomainmotionandfeedingmotion.（2）feedmotionItistherateatwhichthecuttingtooladvancesintotheworkpiece.Itbringsthenewmetalintocuttingconstantlysothatthemachinedsurfaceisproduced.Feedmotionmaybecontinuousmotionorintermittentmotion,ingeneralitutilizeslessmachinepower.Inamachiningprocesstheremaybetwoormorefeedmotions.1.1.1Cuttingmotionsandparameters（1）mainmotionItisthemostnecessaryandimportantmotionintheprocessofremovingtheexcessmetalfromtheworkpiece.Mostofthemaincuttingmotionsarerotationalmotion,usuallyithasthehighestvelocityandconsumesmostofthemachinepower.Thereisonlyonemainmotioninamachiningprocess.（3）resultantmotionandvelocityWhenthemainmotionandthefeedmotiontakepartincuttingsimultaneously,therelativemotionofacertainpointonthecuttingedgeagainsttheworkpiececalledresultantcuttingmotion.Theresultantvelocityofthecuttingmotionisrepresentedbythevectorve,itisequaltothevectorsumofthemainmotionplusthefeedingspeed.1.1.1CuttingmotionsandparametersFig.1.4Resultantcuttingmotioninturning1.Cuttingmotionve=vc+vf(1.1)2.CuttingparameterThespeedofthemainmotionisthecuttingspeedvc.Forarotatingmainmotion:m/sorm/min(1.2)whered－therotationaldiameterofonepointintherotatingworkpieceorcuttingtool（mm)n－numberofrevolutionpersecondorperminute(r/sorr/min)1.1.1Cuttingmotionsandparameters1000dnvcIncuttingprocess,therearethreecuttingparameters:cuttingspeedvc,feedforfeedingspeedvf,andbackengagementofthecuttingedgeap.（1）cuttingspeedFeedfistherelativedisplacementbetweentheworkpieceandthecutteralongthedirectionoffeedingmotionperrevolutionorperstock(mm/r).Feedingspeedvfisthefeedinaunittime(m/sorm/min).Formultipleteethcuttingtools,suchasmillingcutter,reamer,broach,gearhobetc.feedpertooltoothfzmaybemeasured(mm/z).mm/sormm/min（1.3）（2）feed,feedingspeedandfeedpertooth1.1.1CuttingmotionsandparametersnZfnfvzf2.Cuttingparameter（3）backengagementofthecuttingedge1.1.1CuttingmotionsandparametersForturningandplaning,backengagementofthecuttingedgeapisequaltothenormaldistancebetweenthemachinedsurfaceandtheworkpiecesurfacetobecut(mm).Forcylindricalturning:mm(1.4)2mwpdda2mpda2.CuttingparameterFordrilling:mm(1.5)wheredm——diameterofmachinedsurface（mm）dw——diameterofworkpiecesurfacetobecut（mm）1.1.2Essentialdefinitionsfortheworkingpartsofcuttingtools1.ThebasicelementsfortheworkingpartofcuttingtoolrakesurfaceFig.1.5ComponentsoftypicalturningtoolToolbit(Workingpart)mainflanksideflankMaincuttingedgesidecuttingedgetoolnoseshank(1)RakefaceRakefaceAristhesurfaceonwhichthechipflowingout.Thepartadjoiningthemajorcuttingedgeiscalledthemajorrakeface;thepartadjoiningtheminorcuttingedgeiscalledtheminorrakeface.(2)FlankThereareamajorflankandaminorflank.ThemajorflankAαisthesurfacewhichisoppositetothemachiningsurfaceontheworkpiece;theminorflankA’αisthesurfacewhichisoppositetothemachinedsurfac