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外文翻译车床实践及CAD-CAM.doc

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外文翻译车床实践及CAD-CAM.doc

附录2外文翻译(外文部分)ADVANCEDMACHININGPROCESSESAsthehardwareofanadvancedtechnologybecomesmorecomplex,newandvisionaryapproachestotheprocessingofmaterialsintousefulproductscomeintocommonuse.Thishasbeenthetrendinmachiningprocessesinrecentyears..Advancedmethodsofmachinecontrolaswellascompletelydifferentmethodsofshapingmaterialshavepermittedthemechanicaldesignertoproceedindirectionsthatwouldhavebeentotallyimpossibleonlyafewyearsago.Paralleldevelopmentinothertechnologiessuchaselectronicsandcomputershavemadeavailabletothemachinetooldesignermethodsandprocessesthatcanpermitamachinetooltofarexceedthecapabilitiesofthemostexperiencedmachinist.InthissectionwewilllookatCNCmachiningusingchipmakingcuttingtools.CNCcontrollersareusedtodriveandcontrolagreatvarietyofmachinesandmechanisms,Someexampleswouldberoutersinwoodworkinglasers,plasmaarc,flamecutting,andwaterjetsforcuttingofsteelplateandcontrollingofrobotsinmanufacturingandassembly.Thissectionisonlyanoverviewandcannottaketheplaceofaprogrammingmanualforaspecificmachinetool.Becauseofthetremendousgrowthinnumbersandcapabilityofcomputers,changesinmachinecontrolsarerapidlyandconstantlytakingplace.Theexcitingpartofthisevolutioninmachinecontrolsisthatprogrammingbecomeseasierwitheachnewadvancedinthistechnology.AdvantagesofNumericalControlAmanuallyoperatedmachinetoolmayhavethesamephysicalcharacteristicsasaCNCmachine,suchassizeandhorsepower.Theprinciplesofmetalremovalarethesame.Thebiggaincomesfromthecomputercontrollingthemachiningaxesmovements.CNCcontrolledmachinetoolscanbeassimpleasa2axisdrillingmachiningcenterFigureO1.Withadualspindlemachiningcenter,thelowRPM,highhorsepowerspindlegiveshighmetalremovalrates.ThehighRPMspindleallowstheefficientuseofhighcuttingspeedtoolssuchasdiamondsandsmalldiametercuttersFigureO2.Thecuttingtoolsthatremovematerialsarestandardtoolssuchasmillingcutters,drills,boringtools,orlathetoolsdependingonthetypeofmachineused.Cuttingspeedsandfeedsneedtobecorrectasinanyothermachiningoperation.ThegreatestadvantageinCNCmachiningcomesfromtheunerringandrapidpositioningmovementspossible.ACNCmachinedoesdotstopattheendofacuttoplanitsnextmoveitdoesnotgetfatigueditiscapableofuninterruptedmachiningerrorfree,hourafterhour.Amachinetoolisproductiveonlywhileitismakingchips.Sincethechipmakingprocessiscontrolledbytheproperfeedsandspeeds,timesavingscanbeachievedbyfasterrapidfeedrates.Rapidfeedshaveincreasedfrom60to200to400andarenowoftenapproaching1000inchesperminuteIPM.Thesehighfeedratescanposeasafetyhazardtoanyonewithintheworkingenvelopeofthemachinetool.ComplexcontouredshapeswereextremelydifficulttoproductpriortoCNCmachining.CNChasmadethemachiningoftheseshapeseconomicallyfeasible.Designchangesonapartarerelativelyeasytomakebychangingtheprogramthatdirectsthemachinetool.ACNCmachineproducespartswithhighdimensionalaccuracyandclosetoleranceswithouttakingextratimeorspecialprecautions,CNCmachinesgenerallyneedlesscomplexworkholdingfixtures,whichsavestimebygettingthepartsmachinedsooner.Onceaprogramisreadyandproductionparts,eachpartwilltakeexactlythesameamountoftimeasthepreviousone.Thisrepeatabilityallowsforaveryprecisecontrolofproductioncosts.AnotheradvantageofCNCmachiningistheeliminationoflargeinventoriespartscanbemachinedasneeds.Inconventionalproductionoftenagreatnumberofpartsmustbemadeatthesametimetobecosteffective.WithCNCevenonepiececanbemachinedeconomically.Inmanyinstances,aCNCmachinecanperforminonesetupthesameoperationsthatwouldrequireseveralconventionalmachines.WithmodernCNCmachinetoolsatrainedmachinistcanprogramandproductevenasingleparteconomically.CNCmachinetoolsareusedinsmallandlargemachiningfacilitiesandrangeinsizefromtabletopmodelstohugemachiningcenters.InafacilitywithmanyCNCtools,programmingisusuallydonebyCNCprogrammersawayfromtheCNCtools.ThemachinecontrolunitMCUonthemachineisthenusedmostlyforsmallprogramchangesorcorrections.ManufacturingwithCNCtoolsusuallyrequiresthreecategoriesofpersons.Thefirstistheprogrammer,whoisresponsiblefordevelopingmachinereadycode.Thenextpersoninvolvedisthesetupperson,wholoadstherawstorkintotheMCU,checksthatthecorrecttoolsareloaded,andmakesthefirstpart.Thethirdpersonisthemachineandunloadsthefinishedparts.Inasmallcompany,onepersonisexpectedtoperformallthreeofthesetasks.CNCcontrolsaregenerallydividedintotwobasiccategories.OneusesawardaddressformatwithcodedinputssuchasGandMcodes.Theotherusersaconversationalinputconversationalinputisalsocalleduserfriendlyorpromptedinput.Laterinthissectionexamplesofeachoftheseprogrammingformatsinmachiningapplicationswillbedescribes.CAD/CAMAnothermethodofcreatingtoolpathiswiththeuseofaComputeraidedDraftingCADfile.Mostmachinedrawingsarecreatedusingcomputerswiththedescriptionandpartgeometrystoredinthecomputerdatabase.SmartCAM,thoughitsCAMCONNECTION,willreadaCADfileandtransferitsgeometryrepresentsthepartprofile,holes,andsoon.TheprogrammerstillneedstoprepareaJOBPLANwithallthenecessarytools,butinsteadofprogrammingaprofilelinebyline,nowonlyatoolhastobeassignedtoanexistingprofile.Again,usingtheSHOWPATHfunctionwilldisplaythetoolpathforeachtoolandtheirsequence.ConstantresearchanddevelopmentsinCAD/CAMinteractionwillchangehowtheyworkwitheachother.SomeCADandCAMprograms,ifloadedonthesamecomputer,makeitpossibletoswitchbetweenthetwowithafewkeystrokes,designingandprogrammingatthesametime.Theworkareaaroundthemachineneedstobekeptcleanandclearofobstructionstopreventslippingortripping.Machinesurfacesshouldnotbeusedasworktables.Useproperliftingmethodstohandleheavyworkpieces,fixtures,orheavycuttingtools.Makemeasurementsonlywhenthespindlehascometoacompletestandstill.Chipsshouldneverbehandledwithbarehands.Beforestartingthemachinemakesurethattheworkholdingdeviceandtheworkpiecearesecurelyfastened.Whenchangingcuttingtools,protecttheworkpiecebeingmachinedfromdamage,andprotectyourhandsfromsharpcuttingedges.Useonlysharpcuttingtools.Checkthatcuttingtoolsareinstalledcorrectlyandsecurely.Donotoperateanymachinecontrolsunlessyouunderstandtheirfunctionandwhattheywilldo.附录3外文翻译(中文部分)车床实践随着先进科技的硬件变得复杂化,把原料加工成为有用产品的理想的、新的加工手段得到了普遍应用。这已经成为近几年车床加工的发展趋势。先进的车床控制方法和完全不同的材料成形方法还迫使机械设计人员进行前几年还完全没有进行的方向(研究)。其他科技如电子技术和计算机技术的并行发展,使车床设计者有办法让车床具有超过绝大多数经验丰富的机械师(在普通车床上)所具有的加工能力。在这个部分我们来看车床切削使用的工具。CNC控制器能被用来驱动和控制多种车床和机构。举几个例子,如刳刨机进行木料加工激光、离子弧、火焰切削、喷水切削钢板在制造和装配中机器人的控制等。本书的这个部分仅是一般介绍而不能作为专业车床的设计手册。由于计算机能力和容量的巨大增长,车床的控制技术很频繁地发生着变化。在车床控制发展中的精彩部分是在每个先进技术上的使用变得很容易了。NC的优势人工操作车床可能有和CNC车床一样的物理特性,例如马力和尺寸,其金属切削原理也是一样的。CNC最大的好处是通过计算机控制车床刀具的运动,CNC控制的车床可能简单得象2刀钻床或复杂得象5刀的加工中心(如图O1)。两轴的加工车床,其特点是低转速、高马力轴有高进给率,高转速轴允许高效的高速切削刀具如钻石和小直径的刀具的使用(如图O2)。它的切削刀具是标准的刀具如磨床的刀具、钻子、钻探工具或车刀,这些刀具依赖于所使用的车床型号。切削速度和进给量要象在其他操作车床中一样是正确的。CNC车床的最大优势来自无错的和快速的可能运动的控制。车床不会在一次加工完成后停下来计划下一次的运动,它不会疲劳,它是不中断的车床,车床只有在它切削的时候才有生产性。当切削过程被适当的进给量和切削速度控制时,时间的节约可以通过快速的进给率来完成。快速进给从60发展到200到400到现在已接近每分1000英寸了。这样高的进给率对在车床工作区的任何人构成了安全威胁。在CNC车床之前,复杂形状的加工是极困难的。CNC使这些形状的加工制造在经济上是可行的。零件的设计变化通过改变控制车床的程序而相对容易实现。CNC车床不需要额外的时间和特别的预防就可生产高精度的严格公差的零件。CNC使车床不需要复杂的夹具,这使零件很快被加工从而节约了时间。一旦程序准备好并加工零件,每个零件都将花与第一个一样的时间。这个一致性允许很精确地控制加工成本。车床的另一个优势是大量存货的减少,零件可以在需要时再被加工。在传统制造中,为了增加效率,通常一大批零件被同时加工。有了CNC即使一件也能够被经济地加工。在很多情况下,一个CNC车床完成了要建立几台相同传统车床才能做的操作。CAM/CAD另一个确立刀具路径的方法是借助计算机辅助绘图。大多数的机械绘图使用电脑存储了零件平面图形及其注释。格式化的CAM通过它的CAMCONNECTION,可以读一个CAD文件和转移它的图形到它的轮廓基准中去。这图形可表示零件的外形轮廓、孔等等。程序员仍需准备一个工艺卡,含有所用需要的刀具。但相对于用一排排程序来表示外形,现在刀具只用现有的轮廓来表示即可。另外,使用SHOWPATH功能可以显示每个刀具的路径和他们的顺序。CAD/CAM相互影响的方向

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