数控机床与原理外文翻译文献

数控机床与原理外文翻译文献数控机床与原理外文翻译文献(文档含中英文对照即英文原文和中文翻译)FundamentalsNumbercalControlofmachinetoolsMachineToolsMachinetoolsaremachinesforcuttingmetals.Themostimportantofmetalusedinindustryarelathes,drillingmachinesandmillingmachines.Otherkindsofmetalworkingmachinesarenotsowidelyusedinmachiningmetalsasthesethree.Drillingisperfurmedwitharotatingtoolcalledadrill.Mostdrillinginmetaldonewithatwistdrill.Themachineusedfordrillingiscalledadrillpress.Operationssuchasreamingandtapping,arealsoclassifiedasdrilling.Reamingconsistsofremovingasmallamountofmetalfromaholealreadydrilled.Tappingistheprocessofcuttingathreadinsideaholesothatacapscreworboltmaybethreadedintoit.Thelatheiscommonlycalledthefatheroftheentiremachinetoolfamily.Forturningoperations,thelatheusedasingle-point-cuttingtool,whichremovemetalasittravelspasttherevolvingworkpiece.Turningoperationsarerequiredtomakemanydifferentcylindricalshapes,suchasaxes,gearblanks,pulleys,andthreadedshafts.Boringoperationsareperformedtoenlarge,finish,andaccuratelylocateholes.Milingremovesmetalwitharevolving,multiplecuttingedgetoolscalledmilingcutter.Milingcutteraremadeinmanystylesandsizes.Somehaveasfewastwocuttingedgesandothershave30ormore.Milingcanproduceflatorangledsurfaces,grooves,slots,gearteeth,andotherprofile,dependingontheshapeofthecuttersbeingused.Shapingandplanningproduceflatsurfaceswithasingle-point-cuttingtool.Inshaping,thecuttingtoolonashaperreciprocatesormovesbackandforthwhiletheworkisfedautomaticallytowardsthetool.Inplanning,theworkpieceisattachedtoaworktablethatreciprocatespastthecuttingtool.Thecuttingtoolisautomaticallyfedintotheworkpieceasmallamountoneachstroke.Grindingmakesuseofabrasiveparticlestodothecutting.Grindingoperationsmaybeclassifiedasprecisionornon-precision,dependingonthepurpose.Precisiongrindingisconcernedwithgrindingtoclosetolerancesandverysmoothfinish.Non-precisiongrindinginvolvestheremovalofmetalwhereaccuracyisnotimportant.FundamentalsNumberControlControllingamachinetoolbymeansofapreparedprogramisknownasnumericalcontrol,orNC.NCequipmenthasbeendefinedtheElectronicIndustriesAssociation(EIA)as“Asysteminwhichactionsarecontrolledbythedirectinsertionofnumericaldataatsomepoint.Thesystemmustautomaticallyinterpretatleastsomeportionofthisdata.”InatypicalNCsystemthenumericaldatawhichisrequiredforproducingapartismaintainedonapunchedtapeandiscalledthepartprogram.Thepartprogramisarrangedintheformofblockofinformation,whereeachblockcontainsthenumericaldatarequiredtoproduceonesegmentoftheworkpiece.Thepunchedtapeismovedforwardbyoneblockeachtimethecuttingofasegmentiscompleted.Thepunchedcontains,incodedform,alltheinformationneededforprocessingasegmentoftheworkpiece:thesegmentlength,itscuttingspeed,feed,etc..Dimensionalinformation(lenth,width,andradiiofcircles)andthecontourform(linear,circular,orother)aretakenformanengineeringdrawing.Dimensionsaregivenseparatelyforeachaxisofmotion(x,y,etc.).Cuttingspeed,feedrate,andauxiliaryfunction(coolantonandoff,spindledirection,clamp,gearchange,etc.)areprogrammedaccordingtosurfacefinishandtoleracerequirements.PreparingthepartprogramforaNCmachinetoolrequiresapartprogrammer.Thepartprogrammermustpossessknowledgeandexperiencesinmechanicalengineering.PartProgrammersmustbefamiliarwiththefunctionofNCmachinetoolsandmachiningprocessandhavetodecideontheoptimalsequenceofoperations.InNCmachinetoolseachaxisofmotionisequippedwithaseparatedrivingdevicewhichreplacesthehandwheeloftheconventionalmachine.Thedrivingdevicemaybeadirectcurrent(DC)motor,ahydraulicactuator,orasteppingmotor.Thetypeselectedisdeterminedmainlybythepowerrequirementofthemachine.TheNCmachinetoolsystemcontainsthemachinecontrolunit(MCU)andthemachinetoolitself.TheMCUhastoreadanddecodethepartprogram,toprovidethedecodedinstructionstothecontrolloopsofthemachineaxesofmotion,andtocontrolthemachinetooloperation.TheMCUconsistsoftwomainunits:thedataprocessingunit(DPU)andthecontrolloopsunti(CLU).ThefunctionoftheDPUistodecodetheinformationreceivedformthetape,processitandprovidedatatotheDLU.Suchdatacontainsthenewrequiredpositionofeachaxis,itsdirectionofmotionandvelocity,andauxiliarycontrolsignalstorelays.Ontheotherhand,theCLUprovidesasignalannouncingthatthepreviousiscompletedandthattheDPUcanreadanewblockofthepartprogram.TheCLUoperatesthedrivesattachedofthemachinelead-screwsandreceivesfeedbacksignalsontheactualpositionandvelocityofeachoneoftheaxes.Eachlead-screwisequippedwithaseparatedrivingdeviceanfaseparatefeedbackdevice,butthelatterexistsonlyinaclosed-loopsystem.InCNCsystem,theDPUfunctionsareperformedbythecontrolprogramcontainedintheCNCcomputer.ThemajorpartoftheCLU,however,isalwaysimplementedinthemostsophisticatedCNCsystem.NumbericalControlofMachiningProcessNumbericalcontrolofmachinetoolsbycomputershasgreatadvanceinrecentyears.Generally,automaticmachinetoolsareefficientandaccuratewhenlargequantitiesofpartsofthesameshapearerequired,butchangingfromoneautomaticcycletoanotherisalongandexpensiveprocessandwouldonlybecarriedoutforalongrun.Buttherearemanyexampleswhenonlyafewpartsarerequiredanditisinsuchworkthatthecomputer-controlledmachineisvaluable.Therearetwotypesofcomputers-digitalandanalogue.Adigitalcomputerworkswithnumbersgivenindigitalform,adigitbeingoneofacertainsetofsymbolsusedtoshownumbers.Itisthedigitalcomputerwhichisusedinelectronicdataprocessing.Theanaloguecomputerisbasedonananalogyofquantity.Itdealswithphysicalquantitiesandnotnumbers.Inadigitalcontrolsysteminformationformadrawingisputonadiscwhichisputintoacomputerwhichcomputersfromtheinformationtothecontinuousmotionofthecuttingtool.Theoutputisputonadiscwhichisputintothemachinetoolcontroluntilwhenrequired.Onecomputerservicesanumberofmachines.Disccanbestoredandusedanynumberoftimesinfuturecases,simplybyreplayingthemifthesamepartsarewantedagain.Forbestresult,theelectronicequipmentandthemachinetoolmustbedesignedtogether.Thismethodhasalsobeenappliedtothecontrolofoxygencuttingofsteelplates.Whenirregularshapesarerequired,asinshipbuilding,ithasbeenthepracticetomakeamodelandtofollowitsoutlinebyhandcontrol,amethodwhichdoesnotalwaysgiveaccuateresults.Again,informationisprocessedbyaspecialcomputerwhichthenpreparesadiscforuseinthecontrolconsoleofthecuttingmachine.Withthisdiscthemachinecanautomaticallycutplatesofcomplicatedshapesveryaccurately.Thisdevelopmenthasparticularimportanceformakingsteelplatesandisagoodexampleofautomationappliedtobatchproduction.ProgrammingforNCAprogramfornumericalconsistsofasequenceofdirectionsthatcausedaNCmachinetocarryoutacertainoperation,machiningbeingthemostcommonlyusedprocess.ProgrammingforNCmaybedonebyaninternalprogrammingdepartment,ontheshopfloor,orpurchasedfromanoutsidesource.Also,programmingmaybedonemanuallyorwithcomputerassistance.Theprogramcontainsinstructionsandcommands.Geometicinstructionspertaintorelativemovementbetweenthetoolandtheworkpiece.Processinginstructionspertaintospindlespeeds,feed,tools,andsoon.Travelinstructionspertaintothetypeofinterpolationandsloworrapidmovementsofthetoolorworktable.Switchingcommandspertaintoon/offpositionforcoolantsupplies,spindlerotation,directionofspindlerotation,toolchange,workpiecefeeding,clamping,andsoon.(1)Manualprogramming.Manualpartprogrammingconsistsoffirstcalculatingdimensionalrelationshipsofthetool,workpiece,andworktable,basedontheengineeringdrawingsofthepart,andmanufacturingoperationstobeperformedandtheirsequence.Aprogramsheetisthenprepared,whichconsistsofthenecessaryinformationtocarryouttheoperation,suchascuttingtools,spindlespeeds,feeds,depthofcut,cuttingfluids,power,andtoolorworkpiecerelativepositionsandmovements.Basedonthisinformation,thepartprogramisprepared.Usuallyapapertapeisfirstpreparedfortryingoutanddebuggingtheprogram.Dependingonhowoftenitistobeused,thetapemaybemadeofmoredurablemylar.Someonekonledgeableabouttheparticarprocessandabletounderstand,read,andchangepartprogramscandomanualprogramming.Becausetheyarefamiliarwithmachinetoolandprocesscapabilities,skilledmachinistscandomanualprogrammingwithsometraininginprogramming,however,theworkistedious,andtimeconsuming,anduneconomicalandisusedmostlyinsimplepointto-pointapplications.(2)Computer-AidedProgramming.Computer-aidedpartprogramminginvolvesspecialsymbolicprogramminglanguagesthatdeterminethecoordinatepointsofcorners,edges,andsurfacesofthepart.Becausenumericalcontrolinvolvestheinsertionofdataconcerningworkpiecematerialsandprocessingparameters,programmingmustbedonebyoperatorsorprogrammerswhoareknowledgeableabouttherelevantaspectsofthemanufacturingprocessesbeingused.Beforeproductionbegins,programsshouldbeverified,eitherbyviewingasimulationoftheprocessiononaCRTscreenorbymakingthepartfromaninexpensivematerial,suchasaluminum,wood,orplastic,ratherthanthematerialspecifiedforthefinishedpart.MachiningCenterTheflexibilityandversatilityofnumberialcontrolhaveledtothedevelopmentofanewtypeofmachinetoolcalledthemachiningcenter.Usingsimplerworkholdingfixturesandfewercuttingtools,thismachinedosetheworkformerlydoneonseveralmachines.Themachiningcenterisprovidedwithanautomatictoolchanger.OnacommandfromtheNCsystem,thetoolchangearmlocatedabovethespindlerotatesclockwise,simultane-ouslygrippingthetoolinthespindleandanothertoolinaninterchangestationlocatedonthefaceofthemachinewhichisusedtostorethetooltemporarily.Thearmthemmovesforward,removingthetoolsfromthespindleandfromtheinterchangestation.Afterrotatingclockwise180degrees,thearmretracts,insertthenewtoolinthespindle,andplacestheusedtoolintheinterchangesystem,thearmthenreturnstotheoriginalposition.Amechanicalhandinsidethedrumremovesthetoolfromtheinterchangestationandstoresitinthetooldrum.Themachanicalhandremovedthenexttooltobeusedfromthedrumandplacesitintheinterchangestationinpreparationforthenextoperation.Thetoolchangeoperationmaybecompletedin5seconds.Thetooldrumcanholdalargenumberofdifferenttools.Eachtoolholderbeingcoded,thetoolscanbeselectedinarandomorderandinanysequence.MachiningcenterscanalsobeavailablewithoutNC,however,providedwithnumericalcontrol,thepotentialofthesemachinescanbefullyrealized.SoanewgenerationofflexibleintelligentNCmachinesisacurrentmachinemanufacturingindustrytodevelopnumbercontrolprocessoftoolmachineprinciple.Newchallengesforintelligentreconfigurablemanufacturingsystemsareontheagendaforthenextgenerationofmachinetoolcentres.Zerodefectworkpiecesandjust-in-timeproductionaresomeoftheobjectivestobereachedforbetterqualityandhighperformanceproduction.Sustainabilityrequiresaholisticapproachtocovernotonlyflexibleintelligentmanufacturebutalsoproductandservicesactivities.Newroutesphilosophyofpossiblemachinearchitecturewithcharacteristicssuchashybridprocesseswithin-processinspectionandself-healingwillbepresentedwithgreatfeaturesaswellaschallengesrelatedtovariousaspectsofthenextgenerationofintelligentmachinetoolcentres.数控机床及其基本原理机床机床是用于切削金属的机器。工业上使用的机床要属数控车、钻床和铣床最为重要。其它类型的金属切削机床在金属切削加工方面应用不及这三种机床广泛。钻削是由旋转的钻头完成的。大多数金属的钻削有麻花钻来完成。用来进行钻削加工的机床成为钻床，扩孔和攻螺纹也归为钻削，扩孔是从已经钻好的孔上在切除少量的金属。攻螺纹实在内孔上加工出螺纹以使螺杆和螺栓拧进孔内。车床通常被称为所有类型车床的始祖。为了进行车削，当工件旋转时，车床用一把单刃刀具切除金属。用车削可以加工各种圆柱体形状的工件，如轴、齿轮坯、带轮和四杆轴。镗削可以将孔扩大，提高孔的表面质量和加工定位精度高的孔。铣削由旋转的，多切削刃的铣刀来完成，铣刀有多种类型和尺寸。有些铣刀只有两个切削刃，而有些则多达三十或者更多的切削刃。铣刀根据使用的刀具不同能形成平面、斜面、沟槽、狭槽、齿轮和其它外形轮廓。牛头刨床和龙门刨床用单刃刀具来加工平面。用牛头刨床进行加工时，工件朝向刀具自动进给，刀具往复运动；而在用龙门刨床进行加工时，工件安装在工作台上，工作台往复经过刀具切除金属。刀具每完成一个行程则自动向工件进给一个小的进给量。磨削利用磨粒来完成切削工作。根据加工要求，磨削可分为精密磨削和非精密磨削。精密磨削用于公差小河非常光洁的表面，非精密磨削用于在精度要求不高的地方切除多余的金属。数字控制基本原理用准备好的程序控制机床，这种工作方式被称为数字控制或NC。美国电子工业协会把数控设备定义为：“采用在某些点直接插入数字数据来控制操作的系统，此系统必须能够自动解释翻译这些信息中的一部分。”在典型的数控系统中，加工零件所需的数控数据是保存在穿孔带上的，被称为零件程序。零件程序是以信息模块的方式排布的，每一模块中包含了对工件局部进行加工所需的数字信息。当一部分切削完之后，穿孔带移动一个程序块。代码形式的程序块包含了零件分段加工所需的所有信息如分段加工部分长度、切削速度、进给量等。尺寸信息（长、宽及圆半径）和轮廓形状（直线、圆弧或者其它）可以工程图上得到。分别给出每个轴（X、Y等）的运动尺寸，根据表面粗糙度及所需公差对切削速度、进给率及辅助功能（切削液的开、关，主轴的转向、夹紧、换齿轮等）进行编程。要有一个零件编程人员为数控机床准备程序。零件编程人员必须具有机械工程的知识和经验。零件编程人员要熟悉数控机床的功能及加工工艺，并决定最佳加工工序。在数控机床中，，每个轴的运动都要有单独的驱动设备代替普通机床中的手轮来驱动。驱动设备可以是直流电动机、液压发动机或步进电动机，所选的设备的类型主要取决于机床所需的动力。数控机床系统包括有机床控制单元和加工主机本身。机床控制单元（MCU）必须对零件程序读和译码，提供译码指令以控制机床轴的运动并控制机床操作。MCU有两个主要单元：数据处理单元（DPU）和控制回路单元（CLU）。DPU的主要功能是对从穿孔带得到的信息进行译码、处理并给CLU提供数据。这些数据包括每个轴所需要的新位置，运动方向和速度，传递的辅助控制信号。另一方面，CLU提供说明前一部分已经加工完的信号，DPU可以读入新的一段零件程序。CLU操纵连在丝杠上的驱动设备，并接收每个轴的实际位置及速度的反馈信号。每个丝杠都有一个单独的驱动设备和反馈设备，不过后者只出现在闭环系统中。在计算机数控系统中，DPU的功能总是由CNC计算机的控制程序来执行。而CLU的主要部分是在最复杂的CNC系统中实现的。加工过程的数控今年来，基础的计算机数控已经取得了重大的进展。通常形状相同的零件大批量生产时，自动检查显得有效率，加工的精度也高，但由一个自动循环变为另一个自动是一个时间长而又花费高的过程，只能长期运行。但是，又是同一个零件只需要价格几个，这种工作用计算机数控机床进行加工时非常值得的。有计算机数字控制和模拟控制两种类型。数字计算机已数字形式显示数码来工作，一个数字就是一套用以表示数码的符号中的一个符号，它是用在电子数据处理中的数字计算机。模拟计算机是以模拟两位基础的，它处理物理量和非数字量。在数字控制系统中，来自于图样的信息放在磁盘上，计