机械加工介绍--------英文翻译.docx

机械加工介绍（中英文对照）1 LathesLathesaremachinetoolsdesignedprimariIytodoturning,facingandboring,Verylittleturningisdoneonothertypesofmachinetools,andnonecandoitwithequalfacility.Becauselathesalsocandodrillingandreaming,theirversatilitypermitsseveraloperationstobedonewithasinglesetupoftheworkpiece.Consequently,morelathesofvarioustypesareusedinmanufacturingthananyothermachinetool.Theessentialcomponentsofalathearethebed,headstockassembly,tailstockassembly,andtheleadscrewandfeedrod.Thebedisthebackboneofalathe.Itusuallyismadeofwellnormalizedoragedgrayornodularcastironandprovidessheavy,rigidframeonwhichalltheotherbasiccomponentsaremounted.Twosetsofparallel,longitudinalways,innerandouter,arecontainedonthebed,usuallyontheupperside.SomemakersuseaninvertedV-shapeforallfourways,whereasothersutilizeoneinvertedVandoneflatwayinoneorbothsets,Theyareprecision-machinedtoassureaccuracyofalignment.Onmostmodernlathesthewayaresurface-hardenedtoresistwearandabrasion,butprecautionshouldbetakeninoperatingalathetoassurethatthewaysarenotdamaged.Anyinaccuracyinthemusuallymeansthattheaccuracyoftheentirelatheisdestroyed.Theheadstockismountedinafoxedpositionontheinnerways,usuallyattheleftendofthebed.Itprovidesapoweredmeansofrotatingthewordatvariousspeeds.Essentially,itconsistsofahollowspindle,mountedinaccuratebearings,andasetoftransmissiongears-simiIartoatrucktransmission-throughwhichthespindlecanberotatedatanumberofspeeds.Mostlathesprovidefrom8to18speeds,usuallyinageometricratio,andonmodernlathesallthespeedscanbeobtainedmerelybymovingfromtwotofourlevers.Anincreasingtrendistoprovideacontinuouslyvariablespeedrangethroughelectricalormechanicaldrives.Becausetheaccuracyofalatheisgreatlydependentonthespindle,itisofheavyconstructionandmountedinheavybearings,usuallypreloadedtaperedrollerorballtypes.Thespindlehasaholeextendingthroughitslength,throughwhichlongbarstockcanbefed.Thesizeofmaximumsizeofbarstockthatcanbemachinedwhenthematerialmustbefedthroughspindle.Thetailsticdassemblyconsists,essentially,ofthreeparts.Alowercastingfitsontheinnerwaysofthebedandcanslidelongitudinallythereon,withameansforclampingtheentireassemblyinanydesiredlocation,Anuppercastingfitsontheloweroneandcanbemovedtransverselyuponit,onsometypeofkeyedways,topermitaligningtheassemblyisthetailstockquill.Thisisahollowsteelcylinder,usuallyabout51to76mm(2to3inches)indiameter,thatcanbemovedseveralincheslongitudinallyinandoutoftheuppercastingbymeansofahandwheelandscrew.Thesizeofalatheisdesignatedbytwodismensions.Thefirstisknownastheswing.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,askilledmachinistisrequiredforalltheoperations,andsuchpersonsarecostlyandofteninshortsupply.However,muchoftheoperator,stimeisconsumedbysimple,repetitiousadjustmentsandinwatchingchipsbeingmade.Consequently,toreduceoreliminatetheamountofskilledlaborthatisrequired,turretlathes,screwmachines,andothertypesofsemiautomaticandautomaticlatheshavebeenhighlydevelopedandarewidelyusedinmanufacturing.2 NumericalControlOneofthemostfundamentalconceptsintheareaofadvancedmanufacturingtechnologiesisnumericalcontrol(NC).PriortotheadventofNC,allmachinetoolseremanuallyoperatedandcontrolled.Amongthemanylimitationsassociatedwithmanualcontrolmachinetools,perhapsnoneismoreprominentthanthelimitationofoperatorskills.Withmanualcontrol,thequalityoftheproductisdirectlyrelatedtoandlimitedtotheskillsoftheoperator.Numericalcontrolrepresentsthefirstmajorstepawayfromhumancontrolofmachinetools.Numericalcontrolmeansthecontrolofmachinetoolsandothermanufacturingsystemsthroughtheuseofprerecorded,writtensymbolicinstructions.Ratherthanoperatingamachinetool,anNCtechnicianwritesaprogramthatissuesoperationalinstructionstothemachinetool.Foramachinetooltobenumericallycontrolled,itmustbeinterfacedwithadeviceforacceptinganddecodingtheprogrammedinstructions,knownasareader.Numericalcontrolwasdevelopedtoovercomethelimitationofhumanoperators,andithasdoneso.Numericalcontrolmachinesaremoreaccuratethanmanuallyoperatedmachines,theycanproducepartsmoreuniformly,theyarefaster,andthelong-runtoolingcostsarelower.ThedevelopmentofNCledtothedevelopmentofseveralotherinnovationsinmanufacturingtechnology:Electricaldischargemachining,Lasercutting,Electronbeamwelding.Numericalcontrolhasalsomademachinetoolsmoreversatilethantheirmanuallyoperatedpredecessors.AnNCmachinetoolcanautomaticallyproduceawideofparts,eachinvolvinganassortmentofwidelyvariedandcomplexmachiningprocesses.Numericalcontrolhasallowedmanufacturerstoundertaketheproductionofproductsthatwouldnothavebeenfeasiblefromaneconomicperspectiveusingmanuallycontrolledmachinetollsandprocesses.Likesomanyadvancedtechnologies,NCwasborninthelaboratoriesoftheMassachusettsInstituteofTechnology.TheconceptofNCwasdevelopedintheearly1950swithfundingprovidedbytheU.S.AirForce.Initsearlieststages,NCmachineswereabletomadestraightcutsefficientlyandeffectively.However,curvedpathswereaproblembecausethemachinetoolhadtobeprogrammedtoundertakeaseriesofhorizontalandverticalstepstoproduceacurve.Theshorterthestraightlinesmakingupthesteps,thesmootheristhecurve,Eachlinesegmentinthestepshadtobecalculated.Thisproblemledtothedevelopmentin1959oftheAutomaticallyProgrammedTools(APT)language.ThisisaspecialprogramminglanguageforNCthatusesstatementssimilartoEnglishlanguagetodefinethepartgeometry,describethecuttingtoolconfiguration,andspecifythenecessarymotions.ThedevelopmentoftheAPTlanguagewasamajorstepforwardinthefurtherdevelopmentfromthoseusedtoday.Themachineshadhardwiredlogiccircuits.Theinstructionalprogramswerewrittenonpunchedpaper,whichwaslatertobereplacedbymagneticplastictape.Atapereaderwasusedtointerprettheinstructionswrittenonthetapeforthemachine.Together,allofthisrepresentedagiantstepforwardinthecontrolofmachinetools.However,therewereanumberofproblemswithNCatthispointinitsdevelopment.Amajorproblemwasthefragilityofthepunchedpapertapemedium.Itwascommonforthepapertapecontainingtheprogrammedinstructionstobreakortearduringamachiningprocess.Thisproblemwasexacerbatedbythefactthateachsuccessivetimeapartwasproducedonamachinetool,thepapertapecarryingtheprogrammedinstructionshadtobererunthroughthereader.Ifitwasnecessarytoproduce100copiesofagivenpart,itwasalsonecessarytorunthepapertapethroughthereader100separatetines.Fragilepapertapessimplycouldnotwithstandtherigorsofashopfloorenvironmentandthiskindofrepeateduse.Thisledtothedevelopmentofaspecialmagneticplastictape.Whereasthepapercarriedtheprogrammedinstructionsasaseriesofholespunchedinthetape,theplastictapecarriedtheinstructionsasaseriesofmagneticdots.Theplastictapewasmuchstrongerthanthepapertape,whichsolvedtheproblemoffrequenttearingandbreakage.However,itstilllefttwootherproblems.Themostimportantofthesewasthatitwasdifficultorimpossibletochangetheinstructionsenteredonthetape.Tomadeeventhemostminoradjustmentsinaprogramofinstructions,itwasnecessarytointerruptmachiningoperationsandmakeanewtape.Itwasalsostillnecessarytorunthetapethroughthereaderasmanytimesastherewerepartstobeproduced.Fortunately,computertechnologybecamearealityandsoonsolvedtheproblemsofNCassociatedwithpunchedpaperandplastictape.Thedevelopmentofaconceptknownasdirectnumericalcontrol(DNC)solvedthepaperandplastictapeproblemsassociatedwithnumericalcontrolbysimplyeliminatingtapeasthemediumforcarryingtheprogrammedinstructions.Indirectnumericalcontrol,machinetoolsaretied,viaadatatransmissionlink,toahostcomputer.Programsforoperatingthemachinetoolsarestoredinthehostcomputerandfedtothemachinetoolanneededviathedatatransmissionlinkage.Directnumericalcontrolrepresentedamajorstepforwardoverpunchedtapeandplastictape.However,itissubjecttothesamelimitationsasalltechnologiesthatdependonahostcomputer.Whenthehostcomputergoesdown,themachinetoolsalsoexperiencedowntime.Thisproblemledtothedevelopmentofcomputernumericalcontrol.3 TurningTheenginelathe,oneoftheoldestmetalremovalmachines,hasanumberofusefulandhighlydesirableattributes.Todaytheselathesareusedprimarilyinsmallshopswheresmallerquantitiesratherthanlargeproductionrunsareencountered.Theenginelathehasbeenreplacedintoday,sproductionshopsbyawidevarietyofautomaticlathessuchasautomaticofsingle-pointtoolingformaximummetalremoval,andtheuseofformtoolsforfinishonaparwiththefastestprocessingequipmentonthescenetoday.Tolerancesfortheenginelathedependprimarilyontheskilloftheoperator.Thedesignengineermustbecarefulinusingtolerancesofanexperimentalpartthathasbeenproducedontheenginelathebyaskilledoperator.Inredesigninganexperimentalpartforproduction,economicaltolerancesshouldbeused.TurretLathesProductionmachiningequipmentmustbeevaluatednow,morethaneverbefore,thiscriterionforestablishingtheproductionqualificationofaspecificmethod,theturretlathemeritsahighrating.Indesigningforlowquantitiessuchas100or200parts,itismosteconomicaltousetheturretlathe.Inachievingtheoptimumtolerancespossibleontheturretslathe,thedesignershouldstriveforaminimumofoperations.AutomaticScrewMachinesGenerally,automaticscrewmachinesfallintoseveralcategories;single-spindleautomatics,multiple-spindleautomaticsandautomaticchuckingmachines.Originallydesignedforrapid,automaticproductionofscrewsandsimilarthreadedparts,theautomaticscrewmachinehaslongsinceexceededtheconfinesofthisnarrowfield,andtodayplaysavitalroleinthemassproductionofavarietyofprecisionparts.Quantitiesplayanimportantpartintheeconomyofthepartsmachinedontheautomaticscrewmachine.Quantitieslessthanontheautomaticscrewmachine.Thecostofthepartsmachinedcanbereducediftheminimumeconomicallotsizeiscalculatedandthepropermachineisselectedforthesequantities.AutomaticTracerLathesSincesurfaceroughnessdependsgreatlyonmaterialturned,tooling,andfeedsandspeedsemployed,minimumtolerancesthatcanbeheldonautomatictracerlathesarenotnecessarilythemosteconomicaltolerances.Insomecases,tolerancesof0.05mmareheldincontinuousproductionusingbutonecut.groovewidthcanbeheldto0.125mmonsomeparts.Boresandsingle-pointfinishescanbeheldto0.0125mm.Onhigh-productionrunswheremaximumoutputisdesirable,aminimumtoleranceof0.125mmiseconomicalonbothdiameterandlengthofturn4 SimpleMachinesandToolsAWhatDotheSimpleMachinesMean?Simplemachinesaredeviceswhichallowenergytobetransferredfromoneplacetoanother.Withthehelpofmachinesourlivesaremademucheasier.Tomanypeopletheword"machine"meansthingslikeatractor,anelectricdrill,abulldozer,asewingmachineorabicycle.Thesearemachines,buttheyarereallyverycomplicatedones,suchasonesmadeupofmanysimplemachines.Thereareonlyafewkindsofsimplemachines.Theyarethelever,thewheelandaxle,theinclinedplane,gears,pulleysandhydraulics.Simplemachinescandothefollowing:Theyallowenergytobetransferredfromtheplacewhereitisavailabletotheplacewhereitisused.Theycanchangethesizeanddirectionofforce.Certaintypesofmachinesallowustoapplyaverylargeforcetosomethingbyusingasmal1force.Thisiscalledaforceadvantage.Theycanchangethedistanceandspeedwithwhichsomethingismoving.Thisiscalledgivingadistanceorspeedadvantage.Atypicalexampleofsimplemachinesisthelever,whichhasfoundextremelywideuseinourproductionpractice.Someothersimplemachinescanbeseenlikeaseesaw,anaxe,awheelbarrow,apairofscissorsandahammer.Theseareexamplesoflevers.Byusingthese,taskswhichwouldbedifficultforyoutodocanbedonemoreeasily.Aleverisarigidbar.ThecrowbarinFigure1isanexampleofasimplelever.Alllevershavethefollowingparts:1. Thefulcrumisthefixedpointaroundwhichthelevercanturn.2. Theeffortforceistheforceappliedtothelever.Itissometimescalledtheinputforceorsimplytheeffort.3. Theeffortarmisthedistancebetweenthefulcrumandthepointwheretheeffortforceisapplied.4. Theloadforceistheforcemovingtheload.Itistheoutputforceoftheleverandissometimessimplycalledtheload.5. Theloadarmisthedistancefromthefulcrumtothepositionoftheload.Awheelbarrowallowsustoliftaheavyloadbyusingafairlysmallforce.Thewheelbarrowcanbedrawasarigidbarasisshowninfigure2.thewheelaxleactsasthefulcrum.Itcaneasilybeseenthattheeffortarmislongerthantheloadarm.Thisgivesaforceadvantagebecausetheloadforceisgreaterthantheeffortforcethatisapplied.However,theeffortforcehastobemovedmuchfurtherthantheload.Fig.1Acrow-barFig.2AwheelbarrowIfthefulcrumisplacedsothattheloadarmislongerthantheeffortarm,alargeforceisneededtomoveasmallload,butitmovestheloadalongway.Thisgivesaspeedadvantage.Thisideacanbeseeninthefishingrod.Thelargeeffortforceappliedbythefishermanmovesonlyasmallload,thefish.Howeveritdoesallowthefishermantodragthefishinquickly.Oftensimplemachinesaremadeofdoublelevers.Scissors,pliers,nutcrackersandtinsnipsarealldoublelevers.doublelevers双重杠杆effortarm力臂effortforce作用力forceadvantage力增益inamoreconvenientway以某种较为方便的方式inclinedplane斜面loadarm重力臂loadforce荷载力(重力)rigidbar刚性杆speedadvantage速度增益inputforce输入力文中为作用力outputforce输出力文中为载荷力或阻力BToolsandMachinesEachdepartmentinmanufacturingusestoolstodoitsjob.Ingeneral,toolsandmachinesprocess(change)materialsorinformation.Productiondepartmentworkersusetoolstochangematerialsintofinishedproducts.Thefinancedepartmentusescalculatorsandcomputerstokeeptrackofthecompany,sfinances.Marketingworkerssendproductinformationtoconsumersthroughadvertisementsmadewithvideoandaudiorecordingmachines.Workersinmanufacturingmustknowhowtousethetoolsoftheirtrade.DefiningtoolsandmachinesToolsextendhumanabilitiesindoingtheworkofprocessing(changing)materialsorinformation.So,strictlyspeaking,machinesarealsotools.Toolsextendhumanabilitiesbyincreasingthepower,speed,efficiency,accuracy,andproductivityofwork.WecannotdrivenaiIsinboardswithourbarehands,butwecandrivenailswithatool-thehammer.Wecandomathproblemsinourhead,butanelectroniccalculatorisfasterandmoreaccurate.Boththehammerandthecalculatoraretoolsthatextendourabilities.Generally,toolscanbedescribedashandtools,powerhandtools,ormachines.Ahandtoolisthesimplestform.Theuserholdsitinthehandandmovesittoperformwork.ItispoweredOnlybytheuser.Handsaws,screwdrivers,andhandplanesareexamplesofhandtools.Powerhandtoolsareimprovedhandtools.Theuserholdsoneinthehandandmovesittoperf