毕业设计英语论文翻译

LATHESThebasicmachinesthataredesignedprimarilytodoturning,facingandboringarecalledlathes.Verylittleturningisdoneonothertypesofmachinetools,andninecandoitwithequalfacility.Becauselathecandoboring,facing,drilling,andreaminginadditiontoturning,theirversatilitypermitsseveraloperationstobeperformedwithasinglesetupoftheworkpiece.Thisaccountsforthefactthatlathesofvarioustypesaremorewidelyusedinmanufacturingthananyothermachinetool.Lathesinvariousformshaveexistedformorethantwothousandyears.Modemlathesdatefromabout1797,whenHenryMaudsleydevelopedonewithaleadscrew.Itprovidedcontrolled,mechanicalfeedofthetool.ThisingeniousEnglishmanalsodevelopedachange-gearsystemthatcouldconnectthemotionsofthespindleandleadscrewandthusenablethreadstobecut.LatheConstruction.TheessentialcomponentsofalathearedepictedintheblockdiagramofFig.15-1.Thesearethebed,headstockassembly,tailstockassembly,carriageassembly,quick-changegearbox,andtheleadscrewandfeedrod.Thebedisthebackboneofalathe.Itisusuallymadeofwell-normalizedoragedgrayornodularcastironandprovidesaheavy,rigidframeonwhichalltheotherbasiccomponentsaremounted.Twosetsofparallel,longitudinalways,innerandouter,arecontainedonthebed,usuallyontheupperside.SomemakersuseaninvertedV-shapeforallfourways,whereasothersutilizeoneinvertedVandoneflatwayinoneorbothsets.Becauseseveralothercomponentsaremountedand/ormoveonthewaystheymustbemadewithprecisiontoassureaccuracyofalignment.Similarly,properprecautionshouldbetakeninoperatingalathetoassurethatthewaysarenotdamaged.Anyinaccuracyinthemusuallymeansthattheaccuracyoftheentirelatheisdestroyed.Thewaysonmostmodernlathesaresurfacehardenedtooffergreaterresistancetowearandabrasion.Theheadstockismountedinafixedpositionontheinnerwaysatoneendofthelathebed.Itprovidesapoweredmeansofrotatingtheworkatvariousspeeds.Itconsists,essentially,ofahollowspindle,mountedinaccuratebearings,andasetoftransmissiongearssimilartoatrucktransmissionthroughwhichthespindlecanberotatedatanumberofspeeds.Mostlathesprovidefromeighttoeighteenspeeds,usuallyinageometricratio,andonmodernlathesallthespeedscanbeobtainedmerelybymovingfromtwotofourlevers.Anincreasingtrendistoprovideacontinuouslyvariablespeedrangethroughelectricalormechanicaldrives.Becausetheaccuracyofalatheisgreatlydependentonthespindle,itisofheavyconstructionandmountedinheavybearings,usuallypreloadedtaperedrollerorballtypes.Alongitudinalholeextendsthroughthespindlesothatlongbarstockcanbefedthroughit.Thesizeofthisholeisanimportantsizedimensionofalathebecauseitdeterminesthemaximumsizeofbarstockthatcanbemachinedwhenthematerialmustbefedthroughthespindle.Theinnerendofthespindleprotrudesfromthegearboxandcontainsameansformountingvarioustypesofchucks,faceplates,anddogplatesonit.Whereassmalllathesoftenemployathreadedsectiontowhichthechucksarescrewed,mostlargelathesutilizeeithercam-lockorkey-drivetapernoses.Theseprovidealarge-diametertaperthatassurestheaccuratealignmentofthechuck,andamechanismthatpermitsthechuckorfaceplatetobelockedorunlockedinpositionwithoutthenecessityofhavingtorotatetheseheavyattachments.PowerissuppliedtothespindlebymeansofanelectricmotorthroughaV-beltorsilent-chaindrive.Mostmodernlatheshavemotorsoffrom5to15horsepowertoprovideadequatepowerforcarbideandceramictoolsattheirhighcuttingspeeds.Thetailstockassemblyconsists,essentially,ofthreeparts.Alowercastingfitsontheinnerwaysofthebedandcanslidelongitudinallythereon,withameansforclampingtheentireassemblyinanydesiredlocation.Anuppercastingfitsontheloweroneandcanbemovedtransverselyuponitonsometypeofkeyedways.Thistransversemotionpermitsaligningthetailstockandheadstockspindlesandprovidesamethodofturningtapers.Thethirdmajorcomponentoftheassemblyisthetailstockquill.Thisisahollowsteelcylinder,usuallyabout2to3inchesindiameter,thatcanbemovedseveralincheslongitudinallyinandoutoftheuppercastingbymeansofahandwheelandscrew.TheopenendofthequillholeterminatesinaMorsetaperinwhichalathecenter,orvarioustoolssuchasdrills,canbeheld.Agraduatedscale,severalinchesinlength,usuallyisengravedontheoutsideofthequilltoaidincontrollingitsmotioninandoutoftheuppercasting.Alockingdevicepermitsclampingthequillinanydesiredposition.Thecarriageassemblyprovidesthemeansformountingandmovingcuttingtools.ThecarriageisarelativelyflatH-shapedcastingthatrestsandmovesontheoutersetofwaysonthebed.Thetransversebarofthecarriagecontainswaysonwhichthecrossslideismountedandcanbemovedbymeansofafeedscrewthatiscontrolledbyasmallhandwheelandagraduateddial.Throughthecrossslideameansisprovidedformovingthelathetoolinthedirectionnormaltotheaxisofrotationofthework.Onmostlathesthetoolpostactuallyismountedonacompoundrest.Thisconsistsofabase,whichismountedonthecrossslidesothatitcanbepivotedaboutaverticalaxis,andanuppercasting.Theuppercastingismountedonwaysonthisbasesothatitcanbemovedbackandforthandcontrolledbymeansofashortleadscrewoperatedbyahandwheelandacalibrateddial.Manualandpoweredmotionforthecarriage,andpoweredmotionforthecrossslide,isprovidedbymechanismswithintheapron,attachedtothefrontofthecarriage.Manualmovementofthecarriagealongthebediseffectedbyturningahandwheelonthefrontoftheapron,whichisgearedtoapiniononthebackside.Thispinionengagesarackthatisattachedbeneaththeupperfrontedgeofthebedinaninvertedposition.Toimpartpoweredmovementtothecarriageandcrossslide,arotatingfeedrodisprovided.Thefeedrod,whichcontainsakeywaythroughoutmostofitslength,passesthroughthetworeversingbevelpinionsandiskeyedtothem.Eitherpinioncanbebroughtintomeshwithamatingbevelgearbymeansofthereversingleveronthefrontoftheapronandthusprovide“forward”or“reverse”powertothecarriage.Suitableclutchesconnecteithertherackpinionorthecross-slidescrewtoprovidelongitudinalmotionofthecarriageortransversemotionofcrossslide.Forcuttingthreads,asecondmeansoflongitudinaldriveisprovidedbyaleadscrew.Whereasmotionofthecarriagewhendrivenbythefeed-rodmechanismtakesplacethroughafrictionclutchinwhichslippageispossible,motionthroughtheleadscrewisbyadirect,mechanicalconnectionbetweentheapronandtheleadscrew.Thisisachievedbyasplitnut.Bymeansofaclampingleveronthefrontoftheapron,thesplitnutcanbeclosedaroundtheleadscrew.Withthesplitnutclosed,thecarriageismovedalongtheleadscrewbydirectdrivewithoutpossibilityofslippage.Modernlatheshaveaquick-changegearbox.Theinputendofthisgearboxisdrivenfromthelathespindlebymeansofsuitablegearing.Theoutputendofthegearboxisconnectedtothefeedrodandleadscrew.Thus,throughthisgeartrain,leadingfromthespindletothequick-changegearbox,thencetotheleadscrewandfeedrod,andthentothecarriage,thecuttingtoolcanbemadetomoveaspecificdistance,eitherlongitudinallyortransversely,foreachrevolutionofthespindle.Atypicallatheprovides,throughthefeedrod,forty-eightfeedsrangingfrom0.002inchto0.118inchperrevolutionofthespindle,and,throughtheleadscrew,leadsforcuttingforty-eightdifferentthreadsfrom1.5to92perinch.Onsomeolderandsomecheaperlathes,oneortwogearsinthegeartrainbetweenthespindleandthechangegearboxmustbechangedinordertoobtainafullrangeofthreadsandfeeds.CUTTINGTOOLShapeofcuttingtools,particularlytheangles,andtoolmaterialareveryimportantfactors.Thepurposeofthisunitistointroducethecuttingtoolgeometryandtoolmaterials.CuttingToolGeometryAnglesdeterminegreatlynotonlytoollifebutfinishqualityaswell.Generalprinciplesuponwhichcuttingtoolanglesarebaseddonotdependontheparticulartool.Basically,grindingwheelarebeingdesigned.Since,however,thelathe(turning)tool,depictedinFig.14-1,mightbeeasiesttovisualize,itsgeometryisdiscussed.Toolfeatureshavebeenidentifiedbymanynames.Thetechnicalliteratureisfullofconfusingterminology.Thusintheattempttoclearupexistingdisorganizedconceptionsandnomenclature,theAmericanSocietyofMechanicalEngineerspublishedASAStandardB5-22-1950.whatfollowsisbasedonit.Asingle-pointtoolisacuttingtoolhavingonefaceandonecontinuouscuttingedge.ToolanglesidentifiedinFig.14-2areasfollows:(1)Back-rakeangle,(2)Side-rakeangle,(3)End-reliefangle(4)End-reliefangle(5)Side-reliefangle(6)End-cutting-edgeangle,(7)Side-cutting-edgeangle,(8)Noseangle,(9)Noseradius.Toolangle1,onfrontview,istheback-rakeangle.Itistheanglebetweenthetoolfaceandalineparalleltothebaseoftheshankinalongitudinalplaneperpendiculartothetoolbase.Thenthisangleisdownwardfromfronttorearofthecuttingedge,therakeidpositive;whenupwardfromfronttoback,therakeisnegative.Thisangleismostsignificantinthemachiningprocess,becauseitdirectlyaffectsthecuttingforce,finish,andtoollife.Theside-rakeangle,numbered2,measurestheslopeofthefaceinacrossplaneperpendiculartothetoolbase.It,also,isanimportantangle,becauseitdirectschipflowtothesideofthetoolpostandpermitsthetooltofeedmoreeasilyintothework.Theend-reliefangleismeasuredbetweenalineperpendiculartothebaseandtheendflankimmediatelybelowtheendcuttingedge;itisnumbered3inthefigure.Itprovidesclearancebetweenworkandtoolsothatitscutsurfacecanflowbywithminimumrubbingagainstthetool.Tosavetime,aportionoftheendflankofthetoolmaysometimesbeleftunground,havingbeenpreviouslyforgedtosize.Insuchcase,thisend-clearanceangle,numbered4,measuredtotheendflanksurfacebelowthegroundportion,wouldbelargerthanthereliefangle.Oftentheendcuttingedgeisobliquetotheflank.Thereliefangleisthenbestmeasuredinaplanenormaltotheendcuttingedgeperpendiculartothebaseofthetool.Thisclearancepermitsthetooltoadvancemoresmoothlyintothework.Theside-reliefangle,indicatedas5,ismeasuredbetweenthesideflank,justbelowthecuttingedge,andalinethroughthecuttingedgeperpendiculartothebaseofthetool.Thisclearancepermitsthetooltoadvancemoresmoothlyintothework.Angle6istheend-cutting-edgeanglemeasuredbetweentheendcuttingedgeandalineperpendiculartothesideofthetoolshank.Thisanglepreventsrubbingofthecutsurfaceandpermitslongertoollife.Theside-cutting-edgeangle,numbered7,istheanglebetweenthesidecuttingedgeandthesideofthetoolshank.Thetruelengthofcutisalongthisedge.Thustheangledeterminesthedistributionofthecuttingforce.Thegreatertheangle,thelongerthetoollife;butthepossibilityofchatterincreases.Acompromisemust,asusual,bereached.Thenoseangle,number8,istheanglebetweenthetwocomponentcuttingedges.Ifthecornerisroundedoff,thearcsizeisdefinedbythenoseradius9.theradiussizeinfluencesfinishandchatter.CuttingToolMaterialsAlargenumberofcuttingtoolmaterialshavebeendevelopedtomeetthedemandsofhighmetal-removalrates.Themostimportantofthesematerialsandtheirinfluenceoncutterdesign,aredescribedbelow.HighCarbonSteel.Historically,highcarbonsteelwastheearliestcuttingmaterialusedindustrially,butithasnowbeenalmostentirelysupersededsinceitstartstotemperatabout220℃andthisirreversiblesofteningprocesscontinuesastemperatureincreases.Cuttingspeedswithcarbonsteeltoolsarethereforelimitedtoabout0.15m/s(30ftHigh-speedSteel.Toovercomethelowcuttingspeedrestrictionimposedbyplaincarbonsteels,arangeofalloysteels,knownashigh-speedsteels,begantobeintroducedduringtheearlyyearsofthiscentury.Thechemicalcompositionofthesesteelsvariesgreatly,buttheybasicallycontainabout0.7%carbonand4%chromium,withadditionoftungsten,vanadium,molybdenumandcobaltinvaryingpercentages.Theymaintaintheirhardnessattemperaturesuptoabout600℃,butsoftenrapidlyatcuttingspeedsinexcessof1.8m/s(350ft/min),andmanycannotsuccessfullycutmildsteelfasterthan0.75m/s(150ftSinteredCarbides.Carbidecuttingtools,whichweredevelopedinGermanyinthelate1920s,usuallyconsistoftungstencarbideormixturesoftungstencarbideandtitaniumortantalumcarbideinpowderform,sinteredinamatrixofcobaltornickel.Becauseofthecomparativelyhighcostofthistoolmaterialanditslowrupturestrength,itisnormallyproducedintheformoftipswhichareeitherbrazedtoasteelshankormechanicallyclampedinaspeciallydesignedholder.Mechanicallyclampedtooltipsarefrequentlymadeasthrowawayinserts.Whenallthecuttingedgeshavebeenusedtheinsertsarediscarded,adregrindingwouldcostmorethananewtip.Thehighhardnessofcarbidetoolsatelevatedtemperaturesenablesthemtobeusedatmuchfastercuttingspeedsthanhigh-speedsteel(of3-4m/s（600-800ft/min）whencuttingmildsteel).Theyaremanufacturedinseveralgrades,enablingthemtobeusedformostmachiningapplications.Theirearlierbrittlenesshasbeenlargelyovercomebytheintroductionoftoughergrades,whicharefrequentlyusedforinterruptedcutsincludingmanyarduousface-millingoperations.Recently,improvementshavebeenclaimedbyusingtungstencarbidetoolscoatedwithtitaniumcarbideortitaniumnitride(about0.0005mmcoatingthickness).Thesetoolsaremoreresistanttowearthanconventionaltungstencarbidetools,andthereductionininterfacefrictionusingtitaniumnitrideresultsinareductionincuttingforcesandintooltemperatures.Hence,highermetalremovalratesarepossiblewithoutdetrimenttotoollifeoralternativelylongertoollivescouldbeachievedatunchangedmetalremovalrates.Theusesofotherformsofcoatingwithaluminumoxideandpolycrystallinecubicboronnitridearestillinanexperimentalstage,butitislikelythattheywillhaveimportantapplicationswhenmachiningcastiron,hardenedsteelsandhighmeltingpointalloys.Ceramics.Theso-calledceramicgroupofcuttingtoolsrepresentsthemostrecentdevelopmentincuttingtoolmaterials.Theyconsistmainlyofsinteredoxides,usuallyaluminumoxide,andarealmostinvariablyintheformofclampedtips.Becauseofthecomparativecheapnessofceramictipsandthedifficultyofgrindingthemwithoutcausingthermalcracking,theyaremadeasthrow-awayinserts.Ceramictoolsareapost-warintroductionandaremotyetingeneralfactoryuse.Theirmostlikelyapplicationisincuttingmetalatveryhighspeeds,beyondthelimitspossiblewithcarbidetools.Cramicsresisttheformationofabuilt-upedgeandinconsequenceproducegoodsurfacefinishes.Sincethepresentgenerationofmachinetoolsisdesignedwithonlysufficientpowertoexploitcarbidetooling,itislikelythat,forthetimebeing,ceramicswillberestrictedtohigh-speedfinishmachiningwhereissufficientpoweravailableforthelightcutstaken.Theextremebrittlenessofceramictoolshaslargelylimitedtheirusetocontinuouscuts,althoughtheiruseinmillingisnowpossible.Astheyarepoorerconductorsofheatthancarbides,temperaturesattherakefacearehigherthanincarbidetools,althoughthefrictionforceisusuallylower.Tostrengthenthecuttingedge,andconsequentlyimprovethelifeoftheceramictool,asmallchamferorradiusisoftenstonedonthecuttingedge,althoughthisincreasesthepowerconsumption.Diamonds.Forproducingveryfinefinishesof0.05-0.08um（2-3um)onnon-ferrousmetalssuchascopperandaluminum,diamondtoolsareoftenused.Thediamondisbrazedtoasteelshank.Diamondturningandboringareessentiallyfinishingoperations,astheforcesimposedbyanybutthesmallestcutscausethediamondtofractureorbetornfromitsmounting.Undersuitableconditionsdiamondshaveexceptionallylongcuttinglives.Syntheticpolycrystallinediamondsarenowavailableasmechanicallyclampedcuttingtips.Duetotheirhighcosttheyhaveverylimitedapplications,butaresometimesusedformachiningabrasivealuminum-siliconalloys,fusedsilicaandreinforcedplastics.Therandomorientationoftheircrystalsgivesthemimprovedimpactresistance,makingthemsuitableforinterruptedcutting.车床用于车外圆、端面和镗孔等加工机床称作车床。车削极少在其余种类机床上进行，因为其余机床都不能像车床那样方便地进行车削加工。因为车床除了用于车外圆还能用于镗孔、车端面、钻孔和铰孔，车床多功效性能够是共建在一次定位安装中完成多个加工。这种是在生产中普遍使用各种车床比其余种类机床都要多原因。两千多年前就已经有了车床。当代车床能够追溯到大约1797年，那时亨利·莫德斯利创造了一个具备丝杠车床。这种车床能够控制工具机械进给。这位聪明英国人还创造了一个把主轴和丝杠相连变速装置，这么就能够切削螺纹。图15-1中标出了车床主要部件：床身、主轴箱组件、尾架组件、拖板组件、变速齿轮箱、丝杠和光杠。床身是车床基础件。它通常是由经过充分正火或时效处理灰铸铁或者球墨铸铁制成，它是一个坚固刚性框架，全部其余主要部件都安装在床身上。通常在床身上那个面有内外另组平行导轨。一些制造厂生产四个条导轨都采取倒“V”形，而另一些制造厂则将倒“V”形导轨和平面导轨相结合。因为其余部件要安置在导轨上并（或）在导轨上移动，导轨要经过精密加工，以确保其装配精度。一样地，在操作中应该小心，以防止损伤导轨。导轨上任何误差，经常会使整个机床精度遭到破坏。大多数当代车床导轨要进行变面淬火处理，以降低磨损和擦伤，具备更大耐磨性。主轴箱安装在车身一端内导轨固定位置上。它提供动力，使工件在各种速度下旋转。它基本上有一个安装在精密轴承中空心主轴和一系列变速齿轮——类似于卡车变速箱所组成，经过变速齿轮，主轴能够在许多个转速下旋转。大多数车床有8～18种转速，通常按等比级数排列。在当代车床上只需扳动2～4个手柄，就能得到全部档位转速。现在发展趋势是经过电气或机械装置进行无极变速。因为车床精度在很大程度上取决于主轴，所以主轴结构尺寸较大，通常安装在紧密配合重型圆锥滚子轴承或球轴承中。主轴中有一个贯通全长通孔，长棒料能够经过该孔送料。主轴孔大小是车床一个主要尺寸，因为当工件必须经过主轴孔供料时，它确定了能够加工棒料毛坯最大外径尺寸。主轴内端从主轴箱中凸出，其上能够安装多个卡盘、花盘和挡块。而小型车床常有螺纹截面供安装卡盘之用。很多大车床使用偏心夹或键动圆锥轴头。这些附件组成了一个大直径圆锥体，以确保对卡盘进行精准地装配，而且不用旋转这些粗笨附件就能够锁定或松开卡盘或花盘。主轴由电动机经V带或无声链装置提供动力。大多数当代车床都装置有5～15马力电动机，为硬质合金和金属陶瓷合金刀具提供足够动力，进行高速切削。尾座组件主要由三部分组成。底座与床身内侧导轨配合，并能够子导轨上做纵向移动，底座上有一个能够使整个尾座组件加紧在任意位置上装置。尾座安装在底座上，能够沿键槽在底座上横向移动，使尾座与主轴箱中主轴对中并为切削圆锥体提供方便。尾座组件第三部分是尾座套筒，它是一个直径通常在2～3英寸之间钢制空心圆柱轴。经过手轮和螺杆，尾座套筒能够在尾座体中纵向移入和移出几英寸。活动套筒开口一端具备莫氏锥度，能够用于安装顶尖或诸如钻头之类各种刀具。通常在活动套筒外表面刻有几英寸长刻度，以控制尾座前后移动。锁定装置能够使套筒在所需位置上夹紧。拖板组件用于安装和移动切削工具。拖板是一个相对平滑H形铸件，安装在床身外侧导轨上，并能够在上面移动。大拖板上有横向导轨，使横向拖板能够安装在上面，并经过丝杠使其运动，丝杠由一个小手柄和刻度盘控制。横拖板能够带动刀具垂直于工件旋转轴线切削。大多数车床刀架安装在复式刀座上，刀座上有底座，底座安装在横拖板上，可绕垂直轴和上刀架转动。上刀架安装在底座上，可用手轮和刻度盘控制一个短丝杠使其前后移动。溜板箱装在大拖板前面，经过溜板箱内机械装置能够手动和动力驱动大拖板以及动力驱动横拖板。经过转动溜板箱前手轮，能够手动操作拖板沿床身移动。手轮另一端与溜板箱反面小齿轮连接，小齿轮与齿条啮合，齿条倒装在床身前上边缘下面。利用光杆能够将动力传递给大拖板和横拖板。光杆上有一个几乎贯通于整个光杠键槽，光杠经过两个转向相反并用键连接锥齿轮传递动力。经过溜板箱前换向手柄可使啮合齿轮与其中一个锥齿轮啮合，为大拖板提供“向前”或“向后”动力。适当离合器或者齿条小齿轮连接或者与横拖板螺杆连接，是拖板纵向移动或使横拖板横向移动。对于螺纹加工，丝杠提供了第二种纵向移动方法。光杠经过摩擦离合器驱动拖板移动，离合器可能会产生打滑现象。而丝杠产生运动是经过滑板箱与丝杠之间直接机械连接来实现，对于螺母能够实现这种连接。经过溜板箱前面夹紧手柄能够使对开螺母紧紧包合丝杠。当对开螺母闭合时，能够沿丝杠直接驱动拖板，而不会出现打滑可能性。当代车床有一个变速齿轮箱，齿轮箱输入端有车床主轴经过适宜齿轮传动来驱动。齿轮箱输出端与光杠和丝杠连接。主轴就是这么经过齿轮传动链驱动变速齿轮箱，在带动丝杠和光杠，然后带动拖板，刀具就能够按主轴转数纵向地或横向地精准移动。一台经典车床主轴每旋转一圈，经过光杠能够取得从0.002到0.118英寸尺寸范围内48种进给量；而使用丝杠能够车削从1.5到92牙/英寸范围内48种不一样螺纹。一些传统或价廉车床为了能够得到全部进给量和加工出多有螺纹，必须更换主轴和变速箱之间齿轮系中一个或两个齿轮。金属切削刀具刀具形状（尤其是其角度）和材料是刀具两个非常主要原因。本文向大家介绍刀具几何参数和刀具材料。刀具几何参数刀具角度不但在很大程度决定了刀具寿命，