外文翻译--机械加工介绍.doc

题目机械加工介绍学院专业班级姓名学号指导教师外文文献-1-MachiningProcessingIntroduction1LatheLathesaremachinetoolsdesignedprimarilytodoturning,facingandboring,Verylittleturningisdoneonothertypesofmachinetools,andnonecandoitwithequalfacility.Becauselathesalsocandodrillingandreaming,theirversatilitypermitsseveraloperationstobedonewithasinglesetupoftheworkpiece.Consequently,morelathesofvarioustypesareusedinmanufacturingthananyothermachinetool.Theessentialcomponentsofalathearethebed,headstockassembly,tailstockassembly,andtheleadscrewandfeedrod.Thebedisthebackboneofalathe.Itusuallyismadeofwellnormalizedoragedgrayornodularcastironandprovidessheavy,rigidframeonwhichalltheotherbasiccomponentsaremounted.Twosetsofparallel,longitudinalways,innerandouter,arecontainedonthebed,usuallyontheupperside.SommakersuseaninvertedV-shapeforallfourways,whereasothersutilizeoneinvertedVandoneflatwayinoneorbothsets,theyareprecision-machinedtoassureaccuracyofalignment.Onmostmodernlathesthewayaresurface-hardenedtoresistwearandabrasion,butprecautionshouldbetakeninoperatingalathetoassurethatthewaysarenotdamaged.Anyinaccuracyinthemusuallymeansthattheaccuracyoftheentirelatheisdestroyed.-2-Theheadstockismountedinafoxedpositionontheinnerways,usuallyattheleftendofthebed.Itprovidesapoweredmeansofrotatingthewordatvariousspeeds.Essentially,itconsistsofahollowspindle,mountedinaccuratebearings,andasetoftransmissiongears-similartoatrucktransmissionthroughwhichthespindlecanberotatedatanumberofspeeds.Mostlathesprovidefrom8to18speeds,usuallyinageometricratio,andonmodernlathesallthespeedscanbeobtainedmerelybymovingfromtwotofourlevers.Anincreasingtrendistoprovideacontinuouslyvariablespeedrangethroughelectricalormechanicaldrives.Becausetheaccuracyofalatheisgreatlydependentonthespindle,itisofheavyconstructionandmountedinheavybearings,usuallypreloadedtaperedrollerorballtypes.Thespindlehasaholeextendingthroughitslengththroughwhichlongbarstockcanbefed.Thesizeofmaximumsizeofbarstockthatcanbemachinedwhenthematerialmustbefedthroughspindle.Thetailsticdassemblyconsists,essentially,ofthreeparts.Alowercastingfitsontheinnerwaysofthebedandcanslidelongitudinallythereon,withmeansforclampingtheentireassemblyinanydesiredlocation；anuppercastingfitsontheloweroneandcanbemovedtransverselyuponit,onsometypeofkeyedways,topermitaligningtheassemblyisthetailstockquill.Thisishollowsteelcylinder,usuallyabout51to76mm(2to3inches)indiameter,thatcanbemovedseveralincheslongitudinallyinandoutoftheuppercastingbymeansofahandwheelandscrew.Thesizeofalatheisdesignatedbytwodimensions.Thefirstisknownasthe-3-swing.Thisisthemaximumdiameterofworkthatcanberotatedonalathe.Itisapproximatelytwicethedistancebetweenthelineconnectingthelathecentersandthenearestpointontheways,thesecondsizedimensionisthemaximumdistancebetweencenters.Theswingthusindicatesthemaximumworkpiecediameterthatcanbeturnedinthelathe,whilethedistancebetweencentersindicatesthemaximumlengthofworkpiecethatcanbemountedbetweencenters.Enginelathesarethetypemostfrequentlyusedinmanufacturing.Theyareheavy-dutymachinetoolswithallthecomponentsdescribedpreviouslyandhavepowerdriveforalltoolmovementsexceptonthecompoundrest.Theycommonlyrangeinsizefrom305to610mm(12to24inches)swingandfrom610to1219mm(24to48inches)centerdistances,butswingsupto1270mm(50inches)andcenterdistancesupto3658mm(12feet)arenotuncommon.Mosthavechippansandabuilt-incoolantcirculatingsystem.Smallerenginelathes-withswingsusuallynotover330mm(13inches)alsoareavailableinbenchtype,designedforthebedtobemountedonabenchonabenchorcabinet.Althoughenginelathesareversatileandveryuseful,becauseofthetimerequiredforchangingandsettingtoolsandformakingmeasurementsontheworkpiece,thyarenotsuitableforquantityproduction.Oftentheactualchip-productiontineislessthan30%ofthetotalcycletime.Inaddition,askilledmachinistisrequiredforallt