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1、机械加工介绍（中英文对照）1 LathesLathesaremachinetoolsdesignedprimariIytodoturning,facingandboring,Verylittleturningisdoneonothertypesofmachinetools,andnonecandoitwithequalfacility.Becauselathesalsocandodrillingandreaming,theirversatilitypermitsseveraloperationstobedonewithasinglesetupoftheworkpiece.Consequentl
2、y,morelathesofvarioustypesareusedinmanufacturingthananyothermachinetool.Theessentialcomponentsofalathearethebed,headstockassembly,tailstockassembly,andtheleadscrewandfeedrod.Thebedisthebackboneofalathe.Itusuallyismadeofwellnormalizedoragedgrayornodularcastironandprovidessheavy,rigidframeonwhichallth
3、eotherbasiccomponentsaremounted.Twosetsofparallel,longitudinalways,innerandouter,arecontainedonthebed,usuallyontheupperside.SomemakersuseaninvertedV-shapeforallfourways,whereasothersutilizeoneinvertedVandoneflatwayinoneorbothsets,Theyareprecision-machinedtoassureaccuracyofalignment.Onmostmodernlathe
4、sthewayaresurface-hardenedtoresistwearandabrasion,butprecautionshouldbetakeninoperatingalathetoassurethatthewaysarenotdamaged.Anyinaccuracyinthemusuallymeansthattheaccuracyoftheentirelatheisdestroyed.Theheadstockismountedinafoxedpositionontheinnerways,usuallyattheleftendofthebed.Itprovidesapoweredme
5、ansofrotatingthewordatvariousspeeds.Essentially,itconsistsofahollowspindle,mountedinaccuratebearings,andasetoftransmissiongears-simiIartoatrucktransmission-throughwhichthespindlecanberotatedatanumberofspeeds.Mostlathesprovidefrom8to18speeds,usuallyinageometricratio,andonmodernlathesallthespeedscanbe
6、obtainedmerelybymovingfromtwotofourlevers.Anincreasingtrendistoprovideacontinuouslyvariablespeedrangethroughelectricalormechanicaldrives.Becausetheaccuracyofalatheisgreatlydependentonthespindle,itisofheavyconstructionandmountedinheavybearings,usuallypreloadedtaperedrollerorballtypes.Thespindlehasaho
7、leextendingthroughitslength,throughwhichlongbarstockcanbefed.Thesizeofmaximumsizeofbarstockthatcanbemachinedwhenthematerialmustbefedthroughspindle.Thetailsticdassemblyconsists,essentially,ofthreeparts.Alowercastingfitsontheinnerwaysofthebedandcanslidelongitudinallythereon,withameansforclampingtheent
8、ireassemblyinanydesiredlocation,Anuppercastingfitsontheloweroneandcanbemovedtransverselyuponit,onsometypeofkeyedways,topermitaligningtheassemblyisthetailstockquill.Thisisahollowsteelcylinder,usuallyabout51to76mm(2to3inches)indiameter,thatcanbemovedseveralincheslongitudinallyinandoutoftheuppercasting
9、bymeansofahandwheelandscrew.Thesizeofalatheisdesignatedbytwodismensions.Thefirstisknownastheswing.Thisisthemaximumdiameterofworkthatcanberotatedonalathe.Itisapproximatelytwicethedistancebetweenthelineconnectingthelathecentersandthenearestpointontheways,Thesecondsizedimensionisthemaximumdistancebetwe
10、encenters.Theswingthusindicatesthemaximumworkpiecediameterthatcanbeturnedinthelathe,whilethedistancebetweencentersindicatesthemaximumlengthofworkpiecethatcanbemountedbetweencenters.Enginelathesarethetypemostfrequentlyusedinmanufacturing.Theyareheavy-dutymachinetoolswithallthecomponentsdescribedprevi
11、ouslyandhavepowerdriveforalltoolmovementsexceptonthecompoundrest.Theycommonlyrangeinsizefrom305to610mm(12to24inches)swingandfrom610to1219mm(24to48inches)centerdistances,butswingsupto1270mm(50inches)andcenterdistancesupto3658mm(12feet)arenotuncommon.Mosthavechippansandabuilt-incoolantcirculatingsyste
12、m.Smallerenginelathes-withswingsusuallynotover330mm(13inches)-alsoareavailableinbenchtype,designedforthebedtobemountedonabenchonabenchorcabinet.Althoughenginelathesareversatileandveryuseful,becauseofthetimerequiredforchangingandsettingtoolsandformakingmeasurementsontheworkpiece,thyarenotsuitableforq
13、uantityproduction.Oftentheactualchip-productiontineislessthan30%ofthetotalcycletime.Inaddition,askilledmachinistisrequiredforalltheoperations,andsuchpersonsarecostlyandofteninshortsupply.However,muchoftheoperator,stimeisconsumedbysimple,repetitiousadjustmentsandinwatchingchipsbeingmade.Consequently,
14、toreduceoreliminatetheamountofskilledlaborthatisrequired,turretlathes,screwmachines,andothertypesofsemiautomaticandautomaticlatheshavebeenhighlydevelopedandarewidelyusedinmanufacturing.2 NumericalControlOneofthemostfundamentalconceptsintheareaofadvancedmanufacturingtechnologiesisnumericalcontrol(NC)
15、.PriortotheadventofNC,allmachinetoolseremanuallyoperatedandcontrolled.Amongthemanylimitationsassociatedwithmanualcontrolmachinetools,perhapsnoneismoreprominentthanthelimitationofoperatorskills.Withmanualcontrol,thequalityoftheproductisdirectlyrelatedtoandlimitedtotheskillsoftheoperator.Numericalcont
16、rolrepresentsthefirstmajorstepawayfromhumancontrolofmachinetools.Numericalcontrolmeansthecontrolofmachinetoolsandothermanufacturingsystemsthroughtheuseofprerecorded,writtensymbolicinstructions.Ratherthanoperatingamachinetool,anNCtechnicianwritesaprogramthatissuesoperationalinstructionstothemachineto
17、ol.Foramachinetooltobenumericallycontrolled,itmustbeinterfacedwithadeviceforacceptinganddecodingtheprogrammedinstructions,knownasareader.Numericalcontrolwasdevelopedtoovercomethelimitationofhumanoperators,andithasdoneso.Numericalcontrolmachinesaremoreaccuratethanmanuallyoperatedmachines,theycanprodu
18、cepartsmoreuniformly,theyarefaster,andthelong-runtoolingcostsarelower.ThedevelopmentofNCledtothedevelopmentofseveralotherinnovationsinmanufacturingtechnology:Electricaldischargemachining,Lasercutting,Electronbeamwelding.Numericalcontrolhasalsomademachinetoolsmoreversatilethantheirmanuallyoperatedpre
19、decessors.AnNCmachinetoolcanautomaticallyproduceawideofparts,eachinvolvinganassortmentofwidelyvariedandcomplexmachiningprocesses.Numericalcontrolhasallowedmanufacturerstoundertaketheproductionofproductsthatwouldnothavebeenfeasiblefromaneconomicperspectiveusingmanuallycontrolledmachinetollsandprocess
20、es.Likesomanyadvancedtechnologies,NCwasborninthelaboratoriesoftheMassachusettsInstituteofTechnology.TheconceptofNCwasdevelopedintheearly1950swithfundingprovidedbytheU.S.AirForce.Initsearlieststages,NCmachineswereabletomadestraightcutsefficientlyandeffectively.However,curvedpathswereaproblembecauseth
21、emachinetoolhadtobeprogrammedtoundertakeaseriesofhorizontalandverticalstepstoproduceacurve.Theshorterthestraightlinesmakingupthesteps,thesmootheristhecurve,Eachlinesegmentinthestepshadtobecalculated.Thisproblemledtothedevelopmentin1959oftheAutomaticallyProgrammedTools(APT)language.Thisisaspecialprog
22、ramminglanguageforNCthatusesstatementssimilartoEnglishlanguagetodefinethepartgeometry,describethecuttingtoolconfiguration,andspecifythenecessarymotions.ThedevelopmentoftheAPTlanguagewasamajorstepforwardinthefurtherdevelopmentfromthoseusedtoday.Themachineshadhardwiredlogiccircuits.Theinstructionalpro
23、gramswerewrittenonpunchedpaper,whichwaslatertobereplacedbymagneticplastictape.Atapereaderwasusedtointerprettheinstructionswrittenonthetapeforthemachine.Together,allofthisrepresentedagiantstepforwardinthecontrolofmachinetools.However,therewereanumberofproblemswithNCatthispointinitsdevelopment.Amajorp
24、roblemwasthefragilityofthepunchedpapertapemedium.Itwascommonforthepapertapecontainingtheprogrammedinstructionstobreakortearduringamachiningprocess.Thisproblemwasexacerbatedbythefactthateachsuccessivetimeapartwasproducedonamachinetool,thepapertapecarryingtheprogrammedinstructionshadtobererunthroughth
25、ereader.Ifitwasnecessarytoproduce100copiesofagivenpart,itwasalsonecessarytorunthepapertapethroughthereader100separatetines.Fragilepapertapessimplycouldnotwithstandtherigorsofashopfloorenvironmentandthiskindofrepeateduse.Thisledtothedevelopmentofaspecialmagneticplastictape.Whereasthepapercarriedthepr
26、ogrammedinstructionsasaseriesofholespunchedinthetape,theplastictapecarriedtheinstructionsasaseriesofmagneticdots.Theplastictapewasmuchstrongerthanthepapertape,whichsolvedtheproblemoffrequenttearingandbreakage.However,itstilllefttwootherproblems.Themostimportantofthesewasthatitwasdifficultorimpossibl
27、etochangetheinstructionsenteredonthetape.Tomadeeventhemostminoradjustmentsinaprogramofinstructions,itwasnecessarytointerruptmachiningoperationsandmakeanewtape.Itwasalsostillnecessarytorunthetapethroughthereaderasmanytimesastherewerepartstobeproduced.Fortunately,computertechnologybecamearealityandsoo
28、nsolvedtheproblemsofNCassociatedwithpunchedpaperandplastictape.Thedevelopmentofaconceptknownasdirectnumericalcontrol(DNC)solvedthepaperandplastictapeproblemsassociatedwithnumericalcontrolbysimplyeliminatingtapeasthemediumforcarryingtheprogrammedinstructions.Indirectnumericalcontrol,machinetoolsareti
29、ed,viaadatatransmissionlink,toahostcomputer.Programsforoperatingthemachinetoolsarestoredinthehostcomputerandfedtothemachinetoolanneededviathedatatransmissionlinkage.Directnumericalcontrolrepresentedamajorstepforwardoverpunchedtapeandplastictape.However,itissubjecttothesamelimitationsasalltechnologie
30、sthatdependonahostcomputer.Whenthehostcomputergoesdown,themachinetoolsalsoexperiencedowntime.Thisproblemledtothedevelopmentofcomputernumericalcontrol.3 TurningTheenginelathe,oneoftheoldestmetalremovalmachines,hasanumberofusefulandhighlydesirableattributes.Todaytheselathesareusedprimarilyinsmallshops
31、wheresmallerquantitiesratherthanlargeproductionrunsareencountered.Theenginelathehasbeenreplacedintoday,sproductionshopsbyawidevarietyofautomaticlathessuchasautomaticofsingle-pointtoolingformaximummetalremoval,andtheuseofformtoolsforfinishonaparwiththefastestprocessingequipmentonthescenetoday.Toleran
32、cesfortheenginelathedependprimarilyontheskilloftheoperator.Thedesignengineermustbecarefulinusingtolerancesofanexperimentalpartthathasbeenproducedontheenginelathebyaskilledoperator.Inredesigninganexperimentalpartforproduction,economicaltolerancesshouldbeused.TurretLathesProductionmachiningequipmentmu
33、stbeevaluatednow,morethaneverbefore,thiscriterionforestablishingtheproductionqualificationofaspecificmethod,theturretlathemeritsahighrating.Indesigningforlowquantitiessuchas100or200parts,itismosteconomicaltousetheturretlathe.Inachievingtheoptimumtolerancespossibleontheturretslathe,thedesignershoulds
34、triveforaminimumofoperations.AutomaticScrewMachinesGenerally,automaticscrewmachinesfallintoseveralcategories;single-spindleautomatics,multiple-spindleautomaticsandautomaticchuckingmachines.Originallydesignedforrapid,automaticproductionofscrewsandsimilarthreadedparts,theautomaticscrewmachinehaslongsi
35、nceexceededtheconfinesofthisnarrowfield,andtodayplaysavitalroleinthemassproductionofavarietyofprecisionparts.Quantitiesplayanimportantpartintheeconomyofthepartsmachinedontheautomaticscrewmachine.Quantitieslessthanontheautomaticscrewmachine.Thecostofthepartsmachinedcanbereducediftheminimumeconomicall
36、otsizeiscalculatedandthepropermachineisselectedforthesequantities.AutomaticTracerLathesSincesurfaceroughnessdependsgreatlyonmaterialturned,tooling,andfeedsandspeedsemployed,minimumtolerancesthatcanbeheldonautomatictracerlathesarenotnecessarilythemosteconomicaltolerances.Insomecases,tolerancesof0.05m
37、mareheldincontinuousproductionusingbutonecut.groovewidthcanbeheldto0.125mmonsomeparts.Boresandsingle-pointfinishescanbeheldto0.0125mm.Onhigh-productionrunswheremaximumoutputisdesirable,aminimumtoleranceof0.125mmiseconomicalonbothdiameterandlengthofturn4 SimpleMachinesandToolsAWhatDotheSimpleMachines
38、Mean?Simplemachinesaredeviceswhichallowenergytobetransferredfromoneplacetoanother.Withthehelpofmachinesourlivesaremademucheasier.Tomanypeoplethewordmachinemeansthingslikeatractor,anelectricdrill,abulldozer,asewingmachineorabicycle.Thesearemachines,buttheyarereallyverycomplicatedones,suchasonesmadeup
39、ofmanysimplemachines.Thereareonlyafewkindsofsimplemachines.Theyarethelever,thewheelandaxle,theinclinedplane,gears,pulleysandhydraulics.Simplemachinescandothefollowing:Theyallowenergytobetransferredfromtheplacewhereitisavailabletotheplacewhereitisused.Theycanchangethesizeanddirectionofforce.Certainty
40、pesofmachinesallowustoapplyaverylargeforcetosomethingbyusingasmal1force.Thisiscalledaforceadvantage.Theycanchangethedistanceandspeedwithwhichsomethingismoving.Thisiscalledgivingadistanceorspeedadvantage.Atypicalexampleofsimplemachinesisthelever,whichhasfoundextremelywideuseinourproductionpractice.So
41、meothersimplemachinescanbeseenlikeaseesaw,anaxe,awheelbarrow,apairofscissorsandahammer.Theseareexamplesoflevers.Byusingthese,taskswhichwouldbedifficultforyoutodocanbedonemoreeasily.Aleverisarigidbar.ThecrowbarinFigure1isanexampleofasimplelever.Alllevershavethefollowingparts:1. Thefulcrumisthefixedpo
42、intaroundwhichthelevercanturn.2. Theeffortforceistheforceappliedtothelever.Itissometimescalledtheinputforceorsimplytheeffort.3. Theeffortarmisthedistancebetweenthefulcrumandthepointwheretheeffortforceisapplied.4. Theloadforceistheforcemovingtheload.Itistheoutputforceoftheleverandissometimessimplycal
43、ledtheload.5. Theloadarmisthedistancefromthefulcrumtothepositionoftheload.Awheelbarrowallowsustoliftaheavyloadbyusingafairlysmallforce.Thewheelbarrowcanbedrawasarigidbarasisshowninfigure2.thewheelaxleactsasthefulcrum.Itcaneasilybeseenthattheeffortarmislongerthantheloadarm.Thisgivesaforceadvantagebec
44、ausetheloadforceisgreaterthantheeffortforcethatisapplied.However,theeffortforcehastobemovedmuchfurtherthantheload.Fig.1Acrow-barFig.2AwheelbarrowIfthefulcrumisplacedsothattheloadarmislongerthantheeffortarm,alargeforceisneededtomoveasmallload,butitmovestheloadalongway.Thisgivesaspeedadvantage.Thiside
45、acanbeseeninthefishingrod.Thelargeeffortforceappliedbythefishermanmovesonlyasmallload,thefish.Howeveritdoesallowthefishermantodragthefishinquickly.Oftensimplemachinesaremadeofdoublelevers.Scissors,pliers,nutcrackersandtinsnipsarealldoublelevers.doublelevers双重杠杆effortarm力臂effortforce作用力forceadvantage
46、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.Productiondepartmentworke
47、rsusetoolstochangematerialsintofinishedproducts.Thefinancedepartmentusescalculatorsandcomputerstokeeptrackofthecompany,sfinances.Marketingworkerssendproductinformationtoconsumersthroughadvertisementsmadewithvideoandaudiorecordingmachines.Workersinmanufacturingmustknowhowtousethetoolsoftheirtrade.Def
48、iningtoolsandmachinesToolsextendhumanabilitiesindoingtheworkofprocessing(changing)materialsorinformation.So,strictlyspeaking,machinesarealsotools.Toolsextendhumanabilitiesbyincreasingthepower,speed,efficiency,accuracy,andproductivityofwork.WecannotdrivenaiIsinboardswithourbarehands,butwecandrivenail
49、swithatool-thehammer.Wecandomathproblemsinourhead,butanelectroniccalculatorisfasterandmoreaccurate.Boththehammerandthecalculatoraretoolsthatextendourabilities.Generally,toolscanbedescribedashandtools,powerhandtools,ormachines.Ahandtoolisthesimplestform.Theuserholdsitinthehandandmovesittoperformwork.ItispoweredOnlybytheuser.Handsaws,screwdrivers,andhandplanesareexamplesofhandtools.Powerhandtoolsareimprovedhandtools.Theuserholdsoneinthehandandmovesittoperf
