外文翻译-- 车床及其切削加工.doc

毕业设计(论文)外文资料翻译系别：机电信息系专业：机械设计制造及其自动化班级：姓名：学号：外文出处：PneumaticTipsNo.87/1994附件：1.原文；2.译文2013年3月11.原文LathesAndItsCuttingProcessLathesaremachinetoolsdesignedprimarilytodoturning,facing,andboring.Verylittleturningisdoneonothertypesofmachinetools,andnonecandoitwithequalfacility.Becauselathesalsocandodrillingandreaming,theirversatilitypermitsseveraloperationstobedonewithasinglesetupoftheworkpiece.Consequently,morelathesofvarioustypesareusedinmanufacturingthananyothermachinetool.Theessentialcomponentsofalathearethebed,headstockassembly,tailstockassembly,carriageassembly,andtheleadscrewandfeedrod.Thebedisthebackboneofalathe.Itusuallyismadeofwell-normalizedoragedgrayornodularcastironandprovidesaheavy,rigidframeonwhichalltheotherbasiccomponentsaremounted.Twosetsofparallel,longitudinalways,innerandouter,arecontainedonthebed,usuallyontheupperside.SomemakersuseaninvertedV-shapeforallfourways,whereasothersutilizeoneinvertedVandonefiatwayinoneorbothsets.Theyareprecision-machinedtoassureaccuracyofalignment.Onmostmodemlathesthewaysaresurface-hardenedtoresistwearandabrasion,butprecautionshouldbetakeninoperatingalathetoassurethatthewaysarenotdamaged.Anyinaccuracyinthemusuallymeansthattheaccuracyoftheentirelatheisdestroyed.Theheadstockismountedinafixedpositionontheinnerways,usuallyattheleftendofthebed.Itprovidesapoweredmeansofrotatingtheworkatvariousspeeds.Essentially,itconsistsofahollowspindle,mountedinaccuratebearings,andasetoftransmissiongears-similartoatrucktransmission-throughwhichthespindlecanberotatedatanumberofspeeds.Mostlathesprovidefrom8to18speeds,usuallyinageometricratio,andonmodemlathesallthespeedscanbeobtainedmerelybymovingfromtwotofourlevers.Anincreasingtrendistoprovideacontinuouslyvariablespeedrangethroughelectricalormechanicaldrives.Becausetheaccuracyofalatheisgreatlydependentonthespindle,itisofheavyconstructionandmountedinheavybeatings,usuallypreloadedtaperedrollerorballtypes.Thespindlehasaholeextendingthroughitslength,throughwhichlongbarstockcanbefed.Thesizedthisholeisanimportantdimensionofalathebecauseitdetemtinesthemaximumsizeofbarstockthatcanbemachinedwhenthematerialmustbefedthroughspindle.Thetailstockassemblyconsists,essentially,ofthreeparts.Alowercastingfitson2theinnerwaysofthebedandcanslidelongitudinallythereon,withameansforclampingtheentireassemblyinanydesiredlocation.Anuppercastingfitsontheloweroneandcanbemovedtransverselyuponit,onsometypeofkeyedways,topermitaligningthetailstockandheadstockspindles.Thethirdmajorcomponentoftheassemblyisthetailstockquill.Thisisahollowsteelcylinder,usuallyabout51to76mm(2to3inches)indiameter,thatcanbemovedseveralincheslongitudinallyinandoutoftheuppercastingbymeansofahandwheelandscrew.Thesizeofalatheisdesignatedbytwodimensions.Thefirstisknownastheswing.Thisisthemaximumdiameterofworkthatcanberotatedonalathe.Itisapproximatelytwicethedistancebetweenthelineconnectingthelathecentersandthenearestpointontheways.Thesecondsizedimensionisthemaximumdistancebetweencenters.Theswingthusindicatesthemaximumworkpiecediameterthatcanbeturnedinthelathe,whilethedistancebetweencentersindicatesthemaximumlengthofworkpieeethatcanbemountedbetweencenters.Enginelathesarethetypemostfrequentlyusedinmanufacturing.llleyareheavy-dutymachinetoolswithallthecomponentsdescribedpreviouslyandhavepowerdriveforalltoolmovementsexceptonthecompoundrest.Theycommonlyrangeinsizefrom305to610mtn(12to24inches)swingandfrom610to1219mm(24to48inches)centerdistances,butswingsupto1270mm(50inches)andcenterdistancesupto3658mm(12feet)arenottmcommon.Mosthavechippansandabuilt-incoolantcirculatingsystem.Smallerenginelathes-withswingsusuallynotover330mm(13inches)-alsoareavailableinbenchtype,designedforthebedtobemountedonabenchorcabinet.Althoughenginelathesareversatileandveryuseful,becauseofthetimerequiredforchangingandsettingtoolsandformakingmeasurementsontheworkpiece,theyalenotsuitableforquantityproduction.Oftentheactualchip-productiontimeislessthan30%ofthetotalcycletime.Inaddition,askilledmachinistisrequiredforalltheoperations,andsuchpersonsarecostlyandofteninshortsupply.However,muchoftheoperatorstimeisconsumedbysimple,repetitiousadjustmentsandinwatchingchipsbeingmade.Consequently,toreduceoreliminatetheamountofskilledlaborthatisrequired,turretlathes,screwmachines,andothertypesofsemiautomaticandautomaticlatheshavebeenhighlydevelopedandarewidelyusedinmanufacturing.Theenginelathe,oneoftheoldestmetalremovalmachines,hasanumberof3usefulandhighlydesirableattributes.Todaytheselathesareusedprimarilyinsmallshopswheresmallerquantitiesratherthanlargeproductionrunsareencountered.Theenginelathehasbeenreplacedintodaysproductionshopsbyawidevarietyofautomaticlathessuchasautomatictracerlathes,turretlathes,andautomaticscrewmachines.Alltheadvantagesofsingle-pointtoolingformaximummetalremoval,andtheuseofformtoolsforfinishandaccuracy,arenowatthedesignersfingertipswithproductionspeedsonaparwiththefastestprocessingequipmentonthescenetoday.Tolerancesfortheenginelathedependprimarilyontheskilloftheoperator.Thedesignengineermustbecarefulinusingtolerancesofanexperimentalpartthathasbeenproducedontheenginelathebyaskilledoperator.Inredesigninganexperimentalpartforproduction,economicaltolerancesshouldbeused.Productionmachiningequipmentmustbeevaluatednow,morethaneverbefore,intermsofabilitytorepeataccuratelyandrapidly.Applyingthiscriterionforestablishingtheproductionqualificationofaspecificmethod,theturretlathemeritsahighrating.Indesigningforlowquantitiessuchas100or200parts,itismosteconomicaltousetheturretlathe.Inachievingtheoptimumtolerancespossibleontheturretlathe,thedesignershouldstriveforaminimumofoperations.Generally,automaticscrewmachinesfallintoseveralcategories；single-spindleautomatics,multiple-spindleautomaticsandautomaticchuckingmachines.Originallydesignedforrapid,automaticproductionofscrewsandsimilarthreadedpans,theautomaticscrewmachinehaslongsinceexceededtheconfinesofthisnarrowfield,andtodayplaysavitalroleinthemassproductionofavarietyofprecisionparts.Quantitiesplayanimportantpmtintheeconomyofthepartsmachinedontheautomaticscrewmachine.Quantitieslessthan1000partsmaybemoreeconomicaltosetupontheturretlathethanontheautomaticscrewmachine.Thecostofthepansmachinedcanbereducediftheminimumeconomicallotsizeiscalculatedandthepropermachineisselectedforthesequantities.Sincesurfaceroughnessdependsgreatlyuponmaterialtumed,tooling,andfeedsandspeedsemployed,minimumtolerancesthatcanbeheldonautomatictracerlathesarenotnecessarilythemosteconomicaltolerances.Insomecases,tolerancesof±0.05mmareheldincontinuousproductionusingbutonecut.Groovewidthcanbeheldto±0.125mmonsomeparts.Boresandsingle-pointfinishescanbeheldto±0.0125mm.Onhigh-productionrunswhere