外文資料翻譯-1-NCandCNC數(shù)控技術(shù)TheHistoryofNCandCNCDevelopment數(shù)字控制與計(jì)算機(jī)數(shù)字控制的發(fā)展歷史NumericalControl(NC)isanymachiningprocessinwhichtheoperationsareexecutedautomaticallyinsequencesasspecifiedbytheprogramthatcontainstheinformationforthetoolmovements.TheNCconceptwasproposedinthelate1940sbyJohnParsonsofTraverseCity,Michigan.Parsonsrecommendedamethodofautomaticmachinecontrolthatwouldguideamillingcuttertoproduceathru-axiscurveinordertogeneratesmoothprofilesonworkpieces.數(shù)字控制是按照含有機(jī)床(刀具)運(yùn)動(dòng)信息程序所指定的順序自動(dòng)執(zhí)行操作的加工過(guò)程。數(shù)控這一概念是由密歇根洲特拉華城的約翰帕森于20世紀(jì)四十年代后期提出的。為了在工件上加工光滑的輪廓，帕森提出了一種自動(dòng)的機(jī)床控制方式，它能夠引導(dǎo)銑床刀具加工出一種“過(guò)軸曲線”。In1949,TheU.S.AirForceawardedParsonsacontracttodevelopanewtypeofmachinetoolthatwouldbeabletospeedupproductionmethods.ParsonscommissionedtheMassachusettsInstituteofTechnology(M.I.T.)todevelopapracticalimplementationofhisconcept.ScientistsandengineersatM.I.T.builtacontrolsystemforatwo-axismillingmachinethatusedaperforatedpapertapeastheinputmedia.Inashortperiodoftime,allmajormachinetoolmanufacturerswereproducingsomemachineswithNC,butitwasnotuntilthelate1970sthatcomputer-basedNCbecamewidelyused.NCmaturedasanautomationtechnologywheninexpensiveandpowerfulmicroprocessorsreplacedhard-wirelogic-makingcomputer-basedNCsystems.1949年，美國(guó)空軍與帕森簽署了合同，要求開發(fā)一種能夠提高生產(chǎn)率的新型機(jī)床。帕森委托麻省理工學(xué)院(MIT)來(lái)開發(fā)一種新概念機(jī)床，麻省理工學(xué)院的科學(xué)家和工程師研制出了一種用穿孔紙帶作為輸入媒介的二軸聯(lián)動(dòng)銑床控制系統(tǒng)。在較短時(shí)間內(nèi)，當(dāng)時(shí)所有主要的機(jī)床生產(chǎn)商都生產(chǎn)了一些數(shù)控機(jī)床，但直到20世紀(jì)七十年代后期，基于計(jì)算機(jī)的數(shù)字控制才被得到廣泛的使用。只有價(jià)格低廉且功能強(qiáng)大的微處理芯片代替了計(jì)算機(jī)數(shù)控系統(tǒng)中的硬連線邏輯發(fā)生器后，NC才真正成為一門自動(dòng)化技術(shù)。外文資料翻譯-2-WhenNumericalControlisperformedundercomputersupervision,itiscalledComputerNumericalControl(CNC).ComputersarethecontrolunitsofCNCmachines,theyarebuiltinorlinkedtothemachinesviacommunicationschannels.Whenaprogrammerinputsomeinformationintheprogrambytapeandsoon,thecomputercalculatesallnecessarydatatogetthejobdone.當(dāng)數(shù)控機(jī)床在計(jì)算機(jī)監(jiān)控下工作時(shí)，它就被稱為計(jì)算機(jī)數(shù)控機(jī)床(CNC)。計(jì)算機(jī)是CNC機(jī)床的控制單元，它們內(nèi)嵌于數(shù)控機(jī)床或者通過(guò)通訊渠道與數(shù)控機(jī)床聯(lián)接，當(dāng)程序員編程時(shí)，通過(guò)紙帶或磁盤將一些信息輸入，計(jì)算機(jī)將對(duì)一些必要的數(shù)據(jù)進(jìn)行計(jì)算的完成工作。OnthefirstNumericallyControlled(NC)machineswerecontrolledbytape,andbecauseofthat,theNCsystemswereknownastape-controlledmachines.Theywereabletocontrolasingleoperationenteredintothemachinebypunchedormagnetictape.Therewasnopossibilityofeditingtheprogramonthemachine.Tochangetheprogram,anewtapehadtobemade.由于第一臺(tái)數(shù)控機(jī)床的數(shù)據(jù)是由紙帶控制的，因此數(shù)控系統(tǒng)被稱為紙帶控制機(jī)床。它們只能控制由輸入到機(jī)床內(nèi)的紙帶或磁帶所規(guī)定的單一操作，輸入到機(jī)床內(nèi)的程序是不能被編輯的，要改變程序必須重做新紙帶。Todayssystemshavecomputerstocontroldata；theyarecalledComputerNumericallyControlled(CNC)machines.ForbothNCandCNCsystems,workprinciplesarethesame.Onlythewayinwhichtheexecutioniscontrolledisdifferent.Normally,newsystemsarefaster,morepowerful,andmoreversatile當(dāng)今的系統(tǒng)都由計(jì)算機(jī)來(lái)控制數(shù)據(jù)，因而稱之為計(jì)算機(jī)數(shù)控機(jī)床(簡(jiǎn)稱CNC機(jī)床)。NC和CNC系統(tǒng)兩者的工作原理一樣，僅僅控制執(zhí)行的方式不同。新型的數(shù)控系統(tǒng)通常速度更快、功率更大、功能更齊全。TheApplicationsofNC/CNC數(shù)字控制與計(jì)算機(jī)數(shù)字控制的應(yīng)用Sinceitsintroduction,NCtechnologyhasfoundmanyapplications,includinglathesandturningCenters,millingmachinesandmachiningcenters,punches,electricaldischargmachines(EDM)Flamecutters,grinders,andinspectionequipment.themostcomplexCNCmachinetoolsaretheturningcenter,showninFig.4-1(Amodernturningcenterwithaten-stationturretthatacceptsquick-chang外文資料翻譯-3-tools.EachtoolcanbepositionedinSecondswiththepressofabutton).AndthemachinecentershowninFig.4-2(Verticalmachiningcenter,thetoolmagazineisonthemachine.thecontrolpanelontherightcanbeswiveledbytheoperator)andFig.4-3(horizontalmachiningcenter,equippedwithanautomatictoolchanger.toolmagazinescanstore200cttingtools.數(shù)控技術(shù)自創(chuàng)立以來(lái)就得到了廣泛的應(yīng)用，包括車床和車削中心、銑床和加工中心、沖床、電火花(EDM)加工機(jī)床、線切割機(jī)床、磨床以及測(cè)試檢測(cè)裝置等。最復(fù)雜的計(jì)算機(jī)數(shù)控機(jī)床是車削中心，圖41所示一個(gè)具有十轉(zhuǎn)位的刀架能進(jìn)行快速換刀的現(xiàn)代車削中心，立式加工中心如圖42所示(刀具庫(kù)在機(jī)床的左邊。右邊的控制面板可由操作者通過(guò)轉(zhuǎn)臂轉(zhuǎn)動(dòng))，以及臥式加工中心，通過(guò)按下按鈕每把刀可在數(shù)秒鐘內(nèi)定位。如圖43所示(配有自動(dòng)換刀系統(tǒng)。刀具庫(kù)儲(chǔ)備有200把切削工具)。Whenpreparingaprogamforaparticularoperation,theprommermustselectallcuttingdatausingrecommendationsforconventionalmachining.thisincludesproperSelectionofcuttingspeeds,feedrate,toolsandtoolgeometry,andsoon.whentheprogrammerhaschosenallofthenecessaryinformationproperly,theoperatorloadstheprogrammeintothemachineandpressesabuttontostartthecuttingcrycle.theCNCmachinemovesautomaticallyfromonemachingoperationtoanother,changingthecuttingtolsandapplyingthecoolent.inasurprisinglyshorttime,theworkpieceisMachinedaccordingtothehighestqualitystangards.Butthatisnotall.nomatterhowbigtheworkseriesis,allofthepartswillbealmostidenticalinsizeandsurfacefinishing.Atthistimeofadvancedtechnology,withitshighdemandsforsurfacefinishingandtolerancesofcomponentsin,forexample,aerospace,nuclear,andmedicalequipmentmanufacturing,onlyCNCmachinesprovidesuccessfulresults.當(dāng)為某項(xiàng)操作編程時(shí)，程序員必須選擇傳統(tǒng)的加工切削數(shù)據(jù)推薦值。這些切削數(shù)據(jù)包括切削速度、進(jìn)給率、刀具和刀具幾何形狀等。當(dāng)程序員正確選擇所有必要信息后，操作人員將程序載入機(jī)床并按下按鈕，切削循環(huán)就開始。Numericalcontrol(NC)isaformofprogrammableautomationinwhichtheprocessingequipmentiscontrolledbymeansofnumbers,letters,andothersymbols.Thenumbers,letters,andsymbolsarecodedinanappropriateformattodefineaprogramofinstructionsforaparticularworkpartorjob.Theinstructionsareprovided外文資料翻譯-4-byeitherofthetwobinarycodeddecimalsystems:theElectronicIndustriesAssociation(EIA)code,ortheAmericanStandardCodeforInformationInterchange(ASCII).ASCII-codedmachinecontrolunitswillnotaccept.EIAcodedinstructionsandviceversa.Increasingly,however,controlunitsarebeingmadetoacceptinstructionsineithercode.121AutomationoperationbyNCisreadilyadaptabletotheoperationofallmetalworkingmachines.Lathes,millingmachines,drillpresses,boringmachines,grindingmachines,turretpunches,flameorwire-cuttingandweldingmachines,andevenpipebendersareavailablewithnumericalcontrols.數(shù)控技術(shù)是一種利用程序?qū)崿F(xiàn)自動(dòng)控制的技術(shù)，加工制造設(shè)備采用數(shù)控技術(shù)后能由數(shù)字、字符和符號(hào)等進(jìn)行控制。這些數(shù)字、字符和符號(hào)等被編碼成按一定格式定義的指令程序用于一個(gè)特定的加工或工件，這些指令可以采用兩種二進(jìn)制編碼的數(shù)字系統(tǒng)中的任意一種進(jìn)行定義，這兩種二進(jìn)制編碼數(shù)字系統(tǒng)分別為電工協(xié)會(huì)代碼(EIA)和美國(guó)標(biāo)準(zhǔn)信息交換代碼(ASCII)。一