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外文翻译--车床和车削.doc

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外文翻译--车床和车削.doc

1中文英文14页8516字数翻译部分LatheandTurningTheLatheandItsConstructionAlatheisamachinetoolusedprimarilyforproducingsurfacesofrevolutionflatedges.Basedontheirpurpose,construction,numberoftoolsthatcansimultaneouslybemounted,anddegreeofautomation,lathesor,moreaccurately,lathetypemachinetoolscanbeclassifiedasfollows1Enginelathes2Toolroomlathes3Turretlathes4Verticalturningandboringmills5Automaticlathes6SpecialpurposelathesInspiteofthatdiversityoflathetypemachinetools,theyallhaveallhavecommonfeatureswithrespecttoconstructionandprincipleofoperation.Thesefeaturescanbestbeillustratedbyconsideringthecommonlyusedrepresentativetype,theenginelathe.Followingisadescriptionofeachofthemainelementsofanenginelathe,whichisshowninFig.11.1.Lathebed.Thelathebedisthemainframe,involvingahorizontalbeamontwoverticalsupporis.Itisusuallymadeofgreyornodularcastirontodampvibrationsandismadebycasting.Ithasguidewaystoallowthecarriagetoslideeasilylengthwise.Theheightofthelathebedshouldbeappropriatetoenablethetechniciantodohisorherjibeasilyandcomfortably.Headstock.Theheadstockisfixedatthelefthandsideofthelathebedandincludesthespindlewhoseaxisisparalleltotheguidewaysthesildesurfaceofthebed.Thespindleisdriventhroughthegearbox,whichishousedwithintheheadstock.Thefunctionofthegearboxistoprovideanumberofdifferentspindlespeedsusually6upto18speeds.Somemodernlatheshaveheadstockswithinfinitelyvariablespindlespeeds,whichemployfrictional,electrical,orhydraulicdrives.Thespindleisalwayshollow,I.e,ithasathroughholeextendinglengthwise.Barstockscanbefedthrougththatholeifcontinousproductionisadopted.Also,thatholehasatapered2surfacetoallowmountingaplainlathecenter.Theoutersurfaceofthespindleisthreadedtoallowmountingofachuck,afaceplate,orthelike.Tailstock.Thetailstockassemblyconsistsbasicallyofthreeparts,itslowerbase,anintermediatepart,andthequill.Thelowerbaseisacastingthatcanslideonthelathebedalongtheguidewayes,andithasaclampingdevicetoenablelockingtheentiretailstockatanydesiredlocation,dependinguponthelengthoftheworkpiece.Theintermediateparteisacastingthatcanbemovedtransverselytoenablealignmentoftheaxisofthethetailstockwiththatoftheheadstock.Thethirdpart,thequill,isahardenedsteeltube,whichcanbemovedlongitudinallyinandoutoftheintermediatepartasrequired.Thisisachievedthroughtheuseofahandwheelandascrew,aroundwhichanutfixedtothequilliscanbelockedatanypointalongitstravelpathbymeansofaclampingdevice.Thecarriage.Themainfunctionofthecarriageismountingofthecuttingtoolsandgeneratinglongitudinaland/orcrossfeeds.ItisactuallyanHshapedblockthatslidesonthelathebedbetweentheheadstockandtailstockwhilebeingguidedbytheVshapedguidewaysofthebed.Thecarriagecanbemovedeithermanuallyormechanicallybymeansoftheapronandeitherthefeedrodortheleadscrew.Whencuttingscrewthreads,powerisprovidedtothegearboxoftheapronbytheleadscrew.Inallotherturningoperations,itisthefeedrodthatdrivesthecarriage.Theleadscrewgoesthroughapairohalfnuts,whicharefixedtotherearoftheapron.Whenactuatingacertainlever,thehalfnutsareclampedtogetherandengagewiththerotatingleadscrewasasinglenut,whichisfed,togetherwithcarriage,alongthebed.whentheleverisdisengaged,thehalfnutsarereleasedandthecarriagestops.Ontheotherhand,whenthefeedrodisused,itsuppliespowertotheapronthroughawromgear.Thelatteriskeyedtofeedrodandtravelswiththeapronalongthefeedrod,whichhasakeywayextendingtocoveritswholelength.Amodernlatheusuallyhasaquickchangegearboxlocatedundertheheadstockanddrivenfromthespindlethroughatrainofgears.Itisconnectedtoboththefeedrodandtheleadscrewandenablesselectingavarietyoffeedseasilyandrapidlybysimplyshiftingtheappropriatelevers,thequickchangegearboxisemployedinplainturning,facingandthreadcuttingoperations.Sincethatgearboxislinkedtospindle,thedistancethattheapronandthecuttingtooltravelsforeachrevolutionofthespindlecanbecontrolledandisreferredtoasthefeed.LatheCuttingToolsTheshapeandgeometryofthelathetoolsdependuponthepurposeforwhichtheyareemployed.Turningtoolscanbeclassifiedintotowmaingroups,namely,externalcuttingtoolsand3internalcuttingtools,EachofthesegroupsincludethefollowingtypesoftoolsTurningtools.Turingtoolscanbeeitherfinishingorroughturningtools.Roughturningtoolshavesmallnoseradiiandareusedforobtainingthefinalrequireddimensionswithgoodsurfacefinishbymarkingslightdepthofcut.Roughturningtoolscanberight–handorlefthandtypes,dependinguponthedirectionoffeed.Theycanhavestraight,bent,oroffsetshanks.Facingtools.Facingtoolsareemployedinfacingoperationsformachiningplanesideorendsurfaces.Therearetoolsformachininglefthandsidesurfacesandtoolsforrighthandsidesurfaces.Thosesidesurfacesaregeneratedthroughtheuseofthecrossfeed,contrarytoturningoperations,wheretheusuallongitudinalfeedisused.Cutofftools.Cutofftools,whicharesometimescalledpartingtools,servetoseparatetheworkpieceintopartsand/ormachineexternalannualgrooves.Threadcuttingtools.Threadcuttingtoolshaveeithertriangular,square,ortranpezoidalcuttingedges,dependinguponthecrosssectionofthedesiredthread.Also,theplaneanglesofthesetoolsmustalwaysbeidenticaltothoseofthethreadforms.Threadcuttingtoolshavestraightshanksforexternalthreadcuttingandareofthebentshanktypewhencuttinginternalthreads.Formtools.Formtoolshaveedgesespeciallymanufacturedtotakeacertainform,whichisoppositetothedesiredshapeofthemachinedworkpiece.AnHSStoolsisusuallymadeintheformofasinglepiece,contrarytocementedcarbidesorceramic,whicharemadeintheformoftipes.Thelatterarebrazedormechanicallyfastenedtosteelshanks.Fig.1indicatesanarrangementofthislattertype,whichincludesthecarbidetip,thechipbreaker,thepad,theclampingscrewwithawasherandanut,andtheshank..Asthenamesuggests,thefunctionofthechipbreakeristobreaklongchipseverynowandthen,thuspreventingtheformationofverylongtwistedribbonsthatmaycauseproblemsduringthemachiningoperations.Thecarbidetipsorceramictipscanhavedifferentshapes,dependinguponthemachiningoperationsforwhichtheyaretobeemployed.Thetipscaneitherbesolidorwithacentralthroughhole,dependingonwhetherbrazingormechanicalclampingisemployedformountingthetipontheshank.4Fig.1LatheOperationsInthefollowingsection,wediscussthevariousmachiningoperationsthatcanbeperformedonaconventionalenginelathe.Itmustbeborneinmind,however,thatmoderncomputerizednumericallycontrolledlatheshavemorecapabiblitiesanddootheroperations,suchascontouring,forexample.Followingareconventionallatheoperations.Cylindricalturning.Cylindricalturningisthethesimplestandthemostcommonofalllatheoperations.Asinglefullturnoftheworkpiecegenerateacirclewhosecenterfallsonthelatheaxisthismotionisthenreproducednumeroustimesasaresultoftheaxialfeedmotionofthetool.Theresultingmachiningmarksare,therefore,ahelixhavingaverysmallpitch,whichisequaltothefeed.Consequently,themachinedsurfaceisalwayscylindrical.Theaxialfeedisprovidedbythecarriageorthecompoundrest,eithermanuallyorautomatically,whereasthedepthsofcutsiscontrolledbythecrossslide.Inroughingcuts,itisrecommendedthatlargedepthsofcutsupto0.25in.or6mm,dependingupontheworkpiecematerialandsmallerfeedswouldbeused.Ontheotherhand,veryfinefeeds,smallerdepthofcutlessthan0.05in.,or0.4mm,andhighcuttingspeedsarepreferredforfinishingcuts.Facing.Theresultofafacingoperationisaflatsurfacethatiseitherthewholeendsurfaceoftheworkpieceoranannularintermediatesurfacelikeashoulder.Duringafacingoperation,feedisprovidedbythecrossslide,whereasthedepthofcutiscontrolledbythecarriageorcompoundrest.Facingcanbecarriedouteitherfromtheperipheryinwardorfromthecenteroftheworkpieceoutward.Itisobviousthatthemachiningmarksinbothcasestacktheformofaspiral.Usually,itispreferredtoclampthecarriageduringafacingoperation,sincethecuttingforcetendstopushthetooland,ofcourse,thewholecarriageawayfromtheworkpiece.Inmostfacingoperations,theworkpieceisheldinachuckoronafaceplate.Groovecutting.Incutoffandgroovecuttingoperations,onlycrossfeedofthetoolis

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