中國地質(zhì)大學長城學院本科畢業(yè)設計外文資料翻譯系別：工程技術系專業(yè)：機械設計制造及其自動化姓名：何飛學號：052083082012年4月外文資料翻譯譯文CNC技術數(shù)控（NC）是可編程的自動化的一種形式。其加工設備由一系列的數(shù)字、字母和其他符號控制。這些數(shù)字、字母和符號被編成一定的格式，以便為一個特定的工步或者工作定義一個指令程序。當工作改變時，指令程序也隨之改變。這種改變程序的能力使NC適應小、中批量生產(chǎn)。編寫新的程序要比大批量調(diào)換生產(chǎn)設備容易的多。1.NC的基本組成部分一個數(shù)控系統(tǒng)包括以三個組成部分：指令編程、機械控制單元、加工設備。三者之間的關系是：程序?qū)肟刂茊卧刂茊卧苯又笇Ъ庸ぴO備的動作。指令程序是細化的一步步的命令，它控制加工設備。在它的一般形式中，命令涉及到機床主軸和放置工件的工作臺的相對位置。許多先進的指令包含有選擇主軸速度，切削工具等功能。程序編在一個適當?shù)拿浇橹校賹氲娇刂茊卧小Ｔ趲资昵白畛Ｓ玫拿浇槭且挥⒊邔挼拇┛准垘АＳ捎诖┛准垘У膹V泛應用，NC也叫做“紙帶控制”。現(xiàn)在磁帶和軟盤得到了廣泛的應用。加工設備的NC系統(tǒng)的第三個基本組成部分。它是有效工作的執(zhí)行部分。在許多數(shù)控的例子中，加工設備包括工作臺、主軸和驅(qū)動和控制它們的設備。2.控制系統(tǒng)的種類在NC中有兩種基本控制類型：點到點和仿型定位。在點到點系統(tǒng)中（也叫做點定位），機床的每一個軸都單獨驅(qū)動。為了減少不加工時間，機床一最大的速度運動。但刀具達到定位點時開始減速。因此在一個加工過程中，比如鉆削或沖壓，加工過程和回程獨立完成。在孔被鉆出或沖出后，刀具撤回，移動到另一個地方，繼續(xù)下一次加工。從一點到另一點的路徑在一個放面十分重要：為提高效率，所需時間必須最小。點定位主要用于鉆削、蟲牙和立式洗削加工。在仿型定位系統(tǒng)中（也被稱為沿路徑加工系統(tǒng)），定位和加工都沿著指定的路徑，但速度不一樣。因此刀具沿著指定的路徑運動，速度和運動的同步精確控制十分重要。仿型定位系統(tǒng)用于車床、磨床、焊接機械和加工中心中。在幾種基本方法之一的控制之下，刀具沿著路徑發(fā)生微量的移動。在NC程序中，不同的刀具有不同的刀具補償。為使仿型數(shù)控加工中有光滑的路徑，開發(fā)了許多補償方式用以處理這些問題。他們包括：直線插補，圓弧插補，螺旋插補，拋物線插補，三次曲線插補。直線插補是最基本的。當仿型加工路線是直線時用到它。兩軸和三軸直線插補在實際運用中有一定的區(qū)別，但概念上是一致的。程序需要指定直線的起點和終點，并指定沿直線的進給速度。為了得到指定的沿直線的進給速度，插補要計算出兩軸（三軸）的每一軸的進給速度。如果要創(chuàng)建一個圓弧路徑，直線插補是不合適的。因為程序需要指定圓弧和它們各自的終點。圓弧插補已經(jīng)發(fā)展了。它允許路徑的程序包含圓弧，這個圓弧由以下參數(shù)定義：終點坐標、圓弧中心坐標、半徑和沿圓弧加工的方向。創(chuàng)造出的刀具路徑包含一系列的直線線段，但這些線段由插補模型計算，而不是程序本身。刀具沿著每一條線段一條接一條的移動，加工出光滑的圓弧路徑。圓弧插補的限制是圓弧存在的平面必須在一個由CNC系統(tǒng)的二軸定義的平面內(nèi)。螺旋插補使兩軸描述的圓弧插補和第三軸的直線運動結合了起來。它允許在在三維空間里定義一個三維的路徑。拋物線和三次曲線插補利用一個高階方程提供一個復雜的自由曲線。它們通常需要很大的計算量，因此不如直線和圓弧插補常用。它們用于自動化工業(yè)的模具制造中。這些設計中不能精確和方便的由直線和圓弧插補近似。3.加工工具的選擇和加工工藝規(guī)程的制定加工工具的選擇和加工工藝規(guī)程的制定是數(shù)控加工的一個重要的內(nèi)容，它不僅影響到數(shù)控加工的效率，還直接影響到加工質(zhì)量。CAD/CAM技術的發(fā)展，使數(shù)控加工能直接運用CAD設計數(shù)據(jù)，特別是微機和數(shù)控模塊，使設計工藝過程和編程的全過程都由計算機完成，而不需要輸出特定的技術文件。如今，許多CAD/CAM軟件包都提供自動編程功能，這些軟件即時更新編程中遇到的問題，加工刀具的選擇，加工方式的計劃和加工規(guī)范的制定等等。編程人員只需建立先關的參數(shù)，就可以自動完成數(shù)控生產(chǎn)，還可以與數(shù)控模塊通信。因此，在數(shù)控加工中，刀具的選擇和加工規(guī)范的制定完全取決于機床的條件。與此同時也需要編程人員掌握刀具的選擇和工藝規(guī)范的制定原則，因為編程須完全考慮數(shù)控加工的特征。數(shù)控加工經(jīng)常使用的刀具種類和特征數(shù)控加工刀具必須適應高速性，高效性和自動高級特征，應該包括一般刀具和特殊用途的刀具。數(shù)控刀具的劃分有多種方法。許多刀具通過其結構劃分成：（1）整體式刀具（2）裝配式刀具。運用焊接或者機械加緊方式。機械加緊式又可以分為可轉(zhuǎn)位和不可轉(zhuǎn)位兩種。按刀具的材料可分為高速鋼（1）高速鋼刀具（2）硬質(zhì)合金刀具（3）金剛石刀具（4）其他材料刀具。如立方碳化硼刀具，陶瓷刀具等等。還有按切削工藝可分為（1）成型刀具（2）鉆孔刀具。包括麻花鉆、擴孔鉆，忽刀等等（3）鏜刀（4）銑刀等等。為了適應數(shù)控機床對刀具穩(wěn)定性、易更換性等的要求，近幾年裝配式的可轉(zhuǎn)位刀具得到了普遍的應用。占到整個數(shù)控機床刀具的30%--40%，金屬的數(shù)量達到80%--90%。4.數(shù)控程序一個數(shù)控程序包含一系列的能使數(shù)控機床正確加工的指令。NC程序由內(nèi)置程序完成，在商品架上或者從外部資源購買。程序也可以手工或者計算機輔助編程。程序包括指令和命令，G指令定義刀具和工件間的相互運動。P指令定義主軸轉(zhuǎn)速、進給速度、刀具等。T指令定義插補號和工作臺或刀具的快、慢移動。S指令定義主軸轉(zhuǎn)動、換刀和工件的進給等等。（1）手工編程手工編程首先計算刀具、工件和工作臺的相互位置關系。它基于工程圖和制造工藝和它們的順序。然后準備好一個表，其中包括加工特定工序所需的必要信息。例如：切削刀具、主軸轉(zhuǎn)速、進給速度、切削深度、切削液、切削力、刀具或者工件的相對位置和運動。有了這些信息，程序部分就準備好了。通常輸出程序的紙帶要先準備好。手工編程可以由懂得特定加工過程的專業(yè)人士來做，他可以理解、閱讀和改變程序。因為他們熟悉機床刀具，一些有能力的，有技術的工程師通過一些編程訓練就可以手工編程。然而，這項工作十分乏味、耗時。手工編程大多數(shù)情況下用于簡單的點定位中。（2）計算機輔助編程計算機輔助編程有特殊的程序語言。它決定了工件的拐角、邊緣、和表面上的相關點。程序語言是和計算機交流的一種方式。編程人員用這種語言描述加工零件，而由計算機將零件程序轉(zhuǎn)化為數(shù)控機床的執(zhí)行指令。一些有多種特征和應用的語言都可以使用。第一種被運用的類似英語的語言叫做ATP（自動編程工具），它在十九世紀五十年代末開發(fā)出來了。這種語言仍然在點定位和仿型定位中得到了廣泛的應用。計算機輔助編程與手工編程相比有如下優(yōu)勢：，符號語言的簡單應用，減少了編程時間。程序可以存儲大量的與加工過程有關的數(shù)據(jù)，例如：力、速度、進給量、刀具形狀、刀具形狀補償、偏差等。減少了手工編程中的人為錯誤的可能性。簡單的機械順序或機床到機床變化的能力。降低成本（編程只需很少時間）。編程語言的應用不僅導致了高的質(zhì)量，而且使機器指令有了飛速的發(fā)展。而且，模型可以移動到電腦終端，確保了程序功能是想要的。這種方法防止采用不必要的昂貴的機床來加工。選擇一個特定的NC程序語言主要取決于以下因素：制造設備個體專長水平，部件的復雜程度，可用的設備和電腦型號，編程中的時間和成本。因為數(shù)控中數(shù)據(jù)的輸入與工件材料和加工過程有關，程序必須由有機器加工相關方面知識的加工人員或者編程人員完成。在生產(chǎn)開始前，程序必須被驗證，或者通過CRT屏幕觀看加工過程的模型，或者用不貴重的材料模擬加工，例如：鋁、木材或者塑料。5.加工中心當前，許多技術更為先進的車床叫做加工中心。因為，它們除了完成常規(guī)的車削工作之外，還可以完成某些銑削、鉆削工作。加工中心基本上可以認為是轉(zhuǎn)塔車床和銑床的組合體。有時，制造廠商為了增加機床的多用性，還會增加一些其他的性能。6.數(shù)字控制先進制造技術中的一個最基本的概念是數(shù)字控制（NC）。在數(shù)控技術出現(xiàn)之前，所有的機床都是由人工操縱和控制的。在與人工控制的機床有關的很多局限性中，操作者的技能大概是最突出的問題。采用人工控制時，產(chǎn)品的質(zhì)量直接與操作者的技能有關。數(shù)字控制代表了從人工控制機床走出來的第一步。數(shù)字控制意味著采用預先錄制的，存儲的符號指令，控制機床和其他制造系統(tǒng)。一個數(shù)控技師的工作不是去操縱機床，而是編寫能夠發(fā)出機床操縱指令的程序。對于一臺數(shù)控機床，其上必須裝有一個被稱為閱讀機的界面裝置，用來接受和解譯編程指令。發(fā)展數(shù)控技術是為了克服人類操作者的局限性，而且它確實完成了這項工作。數(shù)字控制的機器比人工控制的機器的精度更高、生產(chǎn)的零件的一致性更好、生產(chǎn)的速度更快、而且長期的工藝裝備成本更低。數(shù)控技術的發(fā)展導致制造工藝中的其他幾項新發(fā)明的產(chǎn)生：電火花加工技術，激光切削，電子束焊接。數(shù)字控制還使得機床比它們采用人工操縱的前輩們的用途更為廣泛。一臺數(shù)控機床可以自動生產(chǎn)很多種類的零件，每個零件都可以有不同的和復雜的加工過程。數(shù)控可使生產(chǎn)廠家承擔那些對于采用人工控制的機床和工藝來說，在經(jīng)濟上是不劃算的產(chǎn)品的生產(chǎn)任務。與許多先進技術一樣，數(shù)控誕生于麻省理工學院的實驗室中。數(shù)控這個概念是20世紀50年代初在美國空軍的資助下提出來的。在其最初的階段，數(shù)控機床可以經(jīng)濟和有效地進行直線切割。然而，曲線軌跡成為機床加工的一個問題，在編程時應該采用一系列的水平與豎直的臺階來生成曲線。構成臺階的每個線段越短，曲線就越光滑。臺階中的每個線段都必須經(jīng)過計算。在這個問題促使下，與1959年誕生了自動編程工具（APT）語言。這是一個專門適用于數(shù)控的編程語言，使用類似于英語的語句來定義零件的幾何形狀，描述切削刀具的形狀和規(guī)定必要的運動。APT語言的研究和發(fā)展是在數(shù)控技術進一步發(fā)展過程中的一大進步。最初的數(shù)控系統(tǒng)與今天應用的數(shù)控系統(tǒng)是有很大的差別的。在那時的機床中，只有硬線邏輯電路。指令程序?qū)懺诖┛准垘希ㄋ髞肀凰芰洗艓〈捎脦ч喿x機將寫在紙帶或磁帶上的指令給機器翻譯出來。所有這些共同構成了機床數(shù)字控制方面的巨大的進步。然而，在數(shù)控發(fā)展的這個階段中還存在著許多問題。一個主要問題是穿孔紙帶的易損壞性。在機械加工過程中，載有編程指令信息的紙帶斷裂和被撕壞是常見的事情。在機床上每加工一個零件，都需要將載有編程指令的紙帶放入閱讀機中重新運行一次。因此，這個問題變的很嚴重。如果需要制造100個某種零件，則應該將紙帶分別通過閱讀機100次。易損壞的紙帶顯然不能承受嚴酷的車間環(huán)境和這種重復使用。這就導致了一種專門的塑料磁帶的研制。在紙帶上通過采用一系列的小孔來載有編程指令，而在塑料帶上通過采用一系列的磁點來載有編程指令。塑料帶的強度比紙帶度要高很多，這就可以解決常見的撕壞和斷裂問題。然而，它仍然存在著兩個問題。其中最重要的一個問題是，對輸入帶中的指令進行修改是非常困難的，或者是根本不可能的。即使對指令程序進行最微小的調(diào)整。也必須中斷加工，制作一條新帶。而且?guī)ㄟ^閱讀機的次數(shù)還必須與需要加工的零件的個數(shù)相同。幸運的是，計算機技術的實際應用很快解決了數(shù)控技術中與穿孔紙帶和塑料帶有關的問題。在形成直接數(shù)字控制（DNC）這個概念后，可以不再采用紙帶或塑料帶作為編程指令的載體，這樣就解決了與之有關的問題。在直接數(shù)字控制中，幾臺機床通過數(shù)據(jù)傳輸線路連接到一臺主計算機上。操縱這些機床所需要的程序都存儲在這臺主計算機中。當需要時，通過數(shù)據(jù)傳輸線路提供給每臺機床。直接數(shù)字控制是在穿孔紙帶和塑料帶基礎上的一大進步。然而，它也有著與其他依賴于主計算機的技術一樣的局限性。當主計算機出現(xiàn)故障時，由其控制的所有機床都將停止工作。這個問題促使了計算機數(shù)字控制技術的產(chǎn)生。微處理器的發(fā)展為可編程邏輯控制器和微型計算機的發(fā)展做好了準備。這兩種技術為計算機數(shù)控（CNC）的發(fā)展打下了基礎。采用CNC技術后，每臺機床上都有一個可編程邏輯控制器或者微機對其進行數(shù)字控制。這可以使得程序被輸入和存儲在每臺機器內(nèi)部。它還可以在機床以外編制程序，并且將其下載到每臺機床中。計算機數(shù)控解決了主計算機發(fā)生故障所帶來的問題，但是它產(chǎn)生了另一個被稱為數(shù)據(jù)管理的問題。同一個程序可能要分別裝入十個相互之間沒有通信聯(lián)系的微機中。這個問題正在解決之中，它是通過采用局部區(qū)域網(wǎng)絡將各個微機連接起來，以利于更好地進行數(shù)據(jù)管理。外文原文CNCTECHNOLOGYNumericalcontrol(NC)isaformofprogrammableautomationinwhichtheprocessingequipmentiscontrolledbymeansofnumbers,letters,andothersymbols.Thenumbers,letters,andsymbolsarecodedinanappropriateformattodefineaprogramofinstructionsforaparticularworkpartorjob.Whenthejobchanges,theprogramofinstructionsischanged.ThecapabilitytochangetheprogramiswhatmakesNCsuitableforlow-andmedium-volumeproduction.Itismucheasiertowritenewprogramsthantomakemajoralterationsoftheprocessingequipment.1.BASICCOMPONENTSOFNCAnumericalcontrolsystemconsistsofthefollowingthreebasiccomponents:·Programofinstructions，Machinecontrolunit，Processingequipment。Thegeneralrelationshipamongthethreecomponentsis:theprogramisfedintothecontrolunit,whichdirectstheprocessingequipmentaccordingly.Theprogramofinstructionsisthedetailedstep-by-stepcommandsthatdirecttheprocessingequipment.Initsmostcommonform,thecommandsrefertopositionsofamachinetoolspindlewithrespecttotheworktableonwhichthepartisfixtured.Moreadvancedinstructionsincludeselectionofspindlespeeds,cuttingtool,andotherfunction.Themostcommonmediuminuseoverthelastseveraldecadeshasbeen1-in.-widepunchedtape.Becauseofthewidespreaduseofthepunchedtape,NCissometimescalled“tapecontrol”.However,thisisamisnomerinmodernusageofnumericalcontrol.Comingintousemorerecentlyhavebeenmagnetictapecassettesandfloppydiskettes.Themachinecontrolunit(MCU)consistsoftheelectronicsandcontrolhardwarethatreadandinterprettheprogramofinstructionandconvertitintomechanicalactionsofthemachinetoolorotherprocessingequipment.TheprocessingequipmentisthethirdbasiccomponentofanNCsystem.Itisthecomponentthatperformsusefulwork.Inthemostcommonexampleofnumericalcontrol,onethatperformsmachiningoperations,theprocessingequipmentconsistsoftheworktableandspindleaswellasthemotorsandcontrolsneededtodrivethem.2.TypesOfControlSystemsTherearetwobasictypesofcontrolsystemsinnumericalcontrol:point-to-pointandcontouring.Inthepoint-to-pointsystem,alsocalledpositioning,eachaxisofthemachineisdrivenseparatelybyleadscrewsand,dependingonthetypeofoperation,atdifferentvelocities.Themachinemovesinitiallyatmaximumvelocityinordertoreducenonproductivetimebutdeceleratesasthetoolreachesitsnumericallydefinedposition.Thusinanpotationsuchasdrillingorpunching,thepositioningandcuttingtakeplacesequentially.Aftertheholeisdrilledorpunched,thetoolretracts,movesrapidlytoanotherposition,andrepeatstheoperation.Thepathfollowedfromonepositiontoanotherisimportantinonlyonerespect:Thetimerequiredshouldbeminimizedforefficiency.Point-to-pointsystemsareusedmainlyindrilling,punching,andstraightmillingoperations.Inthecontouringsystem,alsoknownasthecontinuouspathsystem,positioningandcuttingoperationsarebothalongcontrolledpathsbutatdifferentvelocities.Becausethetoolcutsasittravelsalongaprescribedpath,accuratecontrolandsynchronizationofvelocitiesandmovementsareimportant.Thecontouringsystemisusedonlathes,millingmachines,grinders,weldingmachinery,andmachiningcenters.Movementalongthepath,orinterpolation,occursincrementally,byoneofseveralbasicmethods.Inallinterpolations,thepathcontrolledisthatofthecenterofrotationofthetool.Compensationfordifferenttools,differentdiametertools,ortoolwearduringmachining,canbemadeintheNCprogram.Thereareanumberofinterpolationschemesthathavebeendevelopedtodealwiththevariousproblemsthatareencounteredingeneratingasmoothcontinuouspathwithacontouring-typeNCsystem.Theyinclude:·Linearinterpolation，·Circularinterpolation，Helicalinterpolation，Parabolicinterpolation，·Cubicinterpolation。Eachoftheseinterpolationprocedurespermitstheprogrammer(oroperator)togeneratemachineinstructionsforlinearorcurvilinearpaths,usingarelativelyfewinputparameters.TheinterpolationmoduleintheMCUperformsthecalculationsanddirectsthetoolalongthepath.Linearinterpolationisthemostbasicandisusedwhenastraight-linepathistobegeneratedincontinuous-pathNC.Two-axisandthree-axislinearinterpolationroutinesaresometimesdistinguishedinpractice,butconceptuallytheyarethesame.Theprogramisrequiredtospecifythebeginningpointandendpointofthestraightline,andthefeedratethatistobefollowedalongthestraightline.Theinterpolatorcomputesthefeedratesforeachofthetwo(orthree)axesinordertoachievethespecifiedfeedrate.Linearinterpolationforcreatingacircularpathwouldbequiteinappropriatebecausetheprogrammerwouldberequiredtospecifythelinesegmentsandtheirrespectiveendpointsthataretobeusedtoapproximatethecircle.Circularinterpolationschemeshavebeendevelopedthatpermittheprogrammingofapathconsistingofacirculararcbyspecifyingthefollowingparametersofthearc:thecoordinatesofitsendpoints,thecoordinatesofitscenter,itsradius,andthedirectionofthecutteralongthearc.Thetoolpaththatiscreatedconsistsofaseriesofstraight-linesegments,butthesegmentsarecalculatedbytheinterpolationmoduleratherthantheprogrammer.Thecutterisdirectedtomovealongeachlinesegmentonebyoneinordertogeneratethesmoothcircularpath.AlimitationofcircularinterpolationisthattheplaneinwhichthecirculararcexistsmustbeaplanedefinedbytwoaxesoftheNCsystem.Helicalinterpolationcombinesthecircularinterpolationschemefortwoaxesdescribedabovewithlinearmovementofathirdaxis.Thispermitsthedefinitionofahelicalpathinthree-dimensionalspace.Parabolicandcubicinterpolationroutinesareusedtoprovideapproximationsoffree-formcurvesusinghigher-orderequations.Theygenerallyrequireconsiderablecomputationalpowerandarenotascommonaslinearandcircularinterpolation.Theirapplicationsareconcentratedintheautomobileindustryforfabricatingdiesforcarbodypanelsstyledwithfree-formdesignsthatcannotaccuratelyandconvenientlybeapproximatedbycombininglinearandcircularinterpolations.3.ProgrammingForNCAprogramfornumericalcontrolconsistsofasequenceofdirectionsthatcausesanNCmachinetocarryoutacertainoperation,machiningbeingthemostcommonlyusedprocess.ProgrammingforNCmaybedonebyaninternalprogrammingdepartment,ontheshopfloor,orpurchasedfromanoutsidesource.Also,programmingmaybedonemanuallyorwithcomputerassistance.Theprogramcontainsinstructionsandcommands.Geometricinstructionspertaintorelativemovementsbetweenthetoolandtheworkpiece.Processinginstructionspertaintospindlespeeds,feeds,tools,andsoon.Travelinstructionspertaintothetypeofinterpolationandsloworrapidmovementsofthetoolorworktable.Switchingcommandspertaintoon/offpositionforcoolantsupplies,spindlerotation,directionofspindlerotation,toolchanges,workpiecefeeding,clamping,andsoon.(1)ManualProgramming

Manualpartprogrammingconsistsoffirstcalculatingdimensionalrelationshipsofthetool,workpiece,andworktable,basedontheengineeringdrawingsofthepart,andmanufacturingoperationstobeperformedandtheirsequence.Aprogramsheetisthenprepared,whichconsistsofthenecessaryinformationtocarryouttheoperation,suchascuttingtools,spindlespeeds,feeds,depthofcut,cuttingfluids,power,andtoolorworkpieceallyapapertapeisfirstpreparedfortryingoutanddebuggingtheprogram.Dependingonhowoftenitistobeused,thetapemaybemadeofmoredurableMylar.Manualprogrammingcanbedonebysomeoneknowledgeableabouttheparticularprocessandabletounderstand,read,andchangepartprograms.Becausetheyarefamiliarwithmachinetoolsandprocesscapabilities,skilledmachinistscandomanualprogrammingwithsometraininginprogramming.However,theworkistedious,timeconsuming,anduneconomical-andisusedmostlyinsimplepoint-to-pointapplications.(2)Computer-AidedProgramming

Computer-aidedpartprogramminginvolvesspecialsymbolicprogramminglanguagesthatdeterminethecoordinatepointsofcorners,edges,andsurfacesofthepart.Programminglanguageisthemeansofcommunicatingwiththecomputerandinvolvestheuseofsymboliccharacters.Theprogrammerdescribesthecomponenttobeprocessedinthislanguage,andthecomputerconvertsittocommandsfortheNCmachine.Severallanguageshavingvariousfeaturesandapplicationsarecommerciallyavailable.ThefirstlanguagethatusedEnglish-likestatementswasdevelopedinthelate1950sandiscalledAPT(forAutomaticallyProgrammedTools).Thislanguage,initsvariousexpandedforms,isstillthemostwidelyusedforbothpoint-to-pointandcontinuous-pathprogramming.Computer-aidedpartprogramminghasthefollowingsignificantadvantagesovermanualmethods:·Useofrelativelyeasytousesymboliclanguage·Reducedprogrammingtime.Programmingiscapableofaccommodatingalargeamountofdataconcerningmachinecharacteristicsandprocessvariables,suchaspower,speeds,feed,toolshape,compensationfortoolshapechanges,toolwear,deflections,andcoolantuse.·Reducedpossibilityofhumanerror,whichcanoccurinmanualprogramming·Capabilityofsimplechangeoverofmachiningsequenceorfrommachinetomachine.·Lowercostbecauselesstimeisrequiredforprogramming.SelectionofaparticularNCprogramminglanguagedependsonthefollowingfactors:a)

Levelofexpertiseofthepersonnelinthemanufacturingfacility.b)

Complexityofthepart.c)

Typeofequipmentandcomputersavailable.d)

Timeandcostsinvolvedinprogramming.Becausenumericalcontrolinvolvestheinsertionofdataconcerningworkpiecematerialsandprocessingparameters,programmingmustbedonebyoperatorsorprogrammerswhoareknowledgeableabouttherelevantaspectsofthemanufacturingprocessesbeingused.Beforeproductionbegins,programsshouldbeverified,eitherbyviewingasimulationoftheprocessonaCRTscreenorbymakingthepartfromaninexpensivematerial,suchasaluminum,wood,orplastic,ratherthanthematerialspecifiedforthefinishedpart.4.CuttingtoolchoiceandcuttingspecificationsdeterminationinCNCprocessingThecuttingtoolchoiceandthecuttingspecificationsdeterminationisinthenumericalcontrolprocessingcraftimportantcontent,itnotonlyinfluencenumericalcontrolenginebedprocessingefficiency,moreoveraffectstheprocessingqualitydirectly.CAD/TheCAMtechnologydevelopment,enablesinthenumericalcontrolprocessingtobecomedirectlyusingtheCADdesigndatapossibly,speciallythemicrocomputerandthenumericalcontrolenginebedjoint,causesthedesign,thecraftplanandtheprogrammingentireprocesscompletescompletelyonthecomputer,doesnotneedtooutputthespecialtechnologicaldocumentgenerally.Now,manyCAD/TheCAMsoftwarepackageallprovidestheautomaticprogrammingfunction,thesesoftwarearegenerallypromptthecraftplanintheprogrammingcontactsurfacetherelatedquestion,forinstance,cuttingtoolchoice,processingwayplan,cuttingspecificationshypothesisandsoon,programmerssolongashaveestablishedtherelatedparameter,mayautomaticallyproducecompletestheprocessingtheNCprocedureandthetransmissiontothenumericalcontrolenginebed.Therefore,inthenumericalcontrolprocessingcuttingtoolchoiceandthecuttingspecificationsdeterminationiscompletesundertheman-machineinteractivecondition,thisformsthesharpcontrastwiththeordinaryenginebedprocessing,atthesametimealsorequeststheprogrammerstohavetograspthecuttingtoolchoiceandthecuttingspecificationsdeterminationbasicprinciple,whenprogrammingfullconsiderationnumericalcontrolprocessingcharacteristic.Thisarticlethecuttingtoolchoiceandthecuttingspecificationswhichmustfacetothenumericalcontrolprogrammingindeterminedthequestionhascarriedonthediscussion,hasproducedcertainprinciplesandthesuggestion,andtothequestionwhichshouldpayattentionhascarriedonthediscussion.First,numericalcontrolprocessingcommonlyusedcuttingtooltypeandcharacteristicThenumericalcontrolprocessingcuttingtoolmustadaptthenumericalcontrolenginebedhighspeed,ishighlyeffectiveandtheautomatichighcharacteristic,shouldincludethegeneralcuttingtool,thegeneralconnectionhiltandthefewspecial-purposehiltsgenerally.Thehiltmustjointhecuttingtoolandinstallontheenginebedpowerhead,thereforealreadygradualstandardizationandseriation.Thenumericalcontrolcuttingtoolclassificationhasthemanykindsofmethods.Maydivideintoaccordingtothecuttingtoolstructure:(1)Integraltype;(2)Themosaic,usestheweldingormachineclampsthetypeconnection,machineclampsthetypetobepossibletodivideintodoesnotindexandmayindextwokinds;(3)Specialpattern,likecompoundexpressioncuttingtool,absorptionofshocktypecuttingtoolandsoon.Accordingtomakesthematerialwhichthecuttingtoolusestobepossibletodivideinto:(1)High-speedsteelcuttingtool;(2)Hardalloytools;(3)Diamondcuttingtool;(4)Othermaterialcuttingtools,likecubicboronnitridecuttingtool,ceramiccuttingtoolandsoon.Maydivideintofromthecuttingcraft:(1)Theturningcuttingtool,dividestheouterannulus,inthehole,thethread,cutsthecuttingtoolmanykindsofandsoon;(2)Drillstruncatesthecuttingtool,includingdrillbit,reamer,screwtapandsoon;(3)Boringcuttingtool;(4)Millingcuttingtoolandsoon.Inordertoadaptthenumericalcontrolenginebeddurablytothecuttingtool,isstable,easychange,maytradeandsoontherequest,inrecentyearsmachineclampsthetypetobepossibletoindexthecuttingtooltoobtainthewidespreadapplication,reacheshigherauthoritiesinthequantitytotheentirenumericalcontrolcuttingtool30%~40%,themetalexcisionquantityaccountsforthetotal80%~90%.5.MachiningCentersManyoftoday’smoresophisticatedlathesarecalledmachiningcenterssincetheyarecapableofperforming,inadditiontothenormalturningoperations,certainmillinganddrillingoperations.Basically,amachiningcentercanbethoughtofasbeingacombinationturretlatheandmillingmachine.Additionalfeaturesaresometimesincludedbymanufacturerstoincreasetheversatilityoftheirmachines.6.NumericalControlOneofthemostfundamentalconceptsintheareaofadvancedmanufacturingtechnologiesisnumericalcontrol(NC).PriortotheadventofNC,allmachinetoolsweremanuallyoperatedandcontrolled.Amongthemanylimitationsassociatedwithmanualcontrolmachinetools,perhapsnoneismoreprominentthanthelimitationofoperatorskills.Withmanualcontrol,thequalityoftheproductisdirectlyrelatedtoandlimitedtotheskillsoftheoperator.Numericalcontrolrepresentsthefirstmajorstepawayfromhumancontrolofmachinetools.Numericalcontrolmeansthecontrolofmachinetoolsandothermanufacturingsystemsthroughtheuseofprerecorded,writtensymbolicinstructions.Ratherthanoperatingamachinetool,anNCtechnicianwritesaprogramthatissuesoperationalinstructionstothemachinetool.Foramachinetooltobenumericallycontrolled,itmustbeinterfacedwithadeviceforacceptinganddecodingtheprogrammedinstructions,knownasareader.Numericalcontrolwasdevelopedtoovercomethelimitationofhumanoperators,andithasdoneso.Numericalcontrolmachinesaremoreaccuratethanmanuallyoperatedmachines,theycanproducepartsmoreuniformly,theyarefaster,andthelong-runtoolingcostsarelower.ThedevelopmentofNCledtothedevelopmentofseveralotherinnovationsinmanufacturingtechnology:Electricaldischargemachining.Lasercutting.Electronbeamwelding.Numericalcontrolhasalsomademachinetoolsmoreversatilethantheirmanuallyoperatedpredecessors.AnNCmachinetoolcanautomaticallyproduceawidevarietyofparts,eachinvolvinganassortmentofwidelyvariedandcomplexmachiningprocesses.Numericalcontrolhasallowedmanufacturerstoundertaketheproductionofproductsthatwouldnothavebeenfeasiblefromaneconomicperspectiveusingmanuallycontrolledmachinetoolsandprocesses.Likesomanyadvancedtechnologies,NCwasborninthelaboratoriesoftheMassachusettsInstituteofTechnology.TheconceptofNCwasdevelopedintheearly1950swithfundingprovidedbytheU.S.Airforce.Initsearlieststages,NCmachineswereabletomakestraightcutsefficientlyandeffectively.However,curvedpathswereaproblembecausethemachinetoolhadtobeprogrammedtoundertakeaseriesofhorizontalandverticalstepstoproduceacurve.Theshorteristhestraightlinesmakingupthesteps,thesmootheristhecurve.Eachlinesegmentinthestepshadtobecalculated.Thisproblemledtothedevelopmentin1959oftheAutomaticallyProgrammedTools(APT)language.ThisisaspecialprogramminglanguageforNCthatusesstatementssimilartoEnglishlanguagetodefinethepartgeometry,describethecuttingtoolconfiguration,andspecifythenecessarymotions.ThedevelopmentoftheAPTlanguagewasamajorstepforwardinthefurtherdevelopmentofNCtechnology.TheoriginalNCsystemswerevastlydifferentfromthoseusedtoday.Themachineshadhardwiredlogiccircuits.Theinstructionalprogramswerewrittenonpunchedpaper,whichwaslatertobereplacedbymagneticplastictape.Atapereaderwasusedtointerprettheinstructionswrittenonthetapeforthemachine.Together,allofthisrepresentedagiantstepforwardinthecontrolofmachinetools.However,therewereanumberofproblemswithNCatthispointinitsdevelopment.Amajorproblemwasthefragilityofthepunchedpapertapemedium.Itwascommonforthepapertapecontainingtheprogrammedinstructionstobreakortearduringamachiningprocess.Thisproblemwasexacerbatedbythefactthateachsuccessivetimeapartwasproducedonamachinetool,thepapertapecarryingtheprogrammedinstructionshadtobererunthroughthereader.Ifitwasnecessarytoproduce100copiesofagivenpart,itwasalsonecessarytorunthepapertapethroughthereader100separatetimes.Fragilepapertapessimplycouldnotwithstandtherigorsofashopfloorenvironmentandthiskindofrepeateduse.Thisledtothedevelopmentofaspecialmagneticplastictape.Whereasthepapertapecarriedtheprogrammedinstructionsasaseriesofholespunchedinthetape,theplastictapecarriedtheinstructionsasaseriesofholespunchedinthetape,theplastictapecarriedtheinstructionsasaseriesofmagneticdots.Theplastictapewasmuchstrongerthanthepapertaps,whichsolvedtheproblemoffrequenttearingandbreakage.However,itstilllefttwootherproblems.Themostimportantofthesewasthatitwasdifficultorimpossibletochangetheinstructionsenteredonthetape.Tomakeeventhemostminoradjustmentsinaprogramofinstructions,itwasnecessarytointerruptmachiningoperationsandmakeanewtape.Itwasalsostillnecessarytorunthetapethroughthereaderasmanytimesastherewerepartstobeproduced.Fortunately,computertechnologybecamearealityandsoonsolvedtheproblemsofNCassociatedwithpunchedpaperandplastictape.Thedevelopmentofaconceptknownasdirectnumericalcontrol(DNC)solvedthepaperandplastictapeproblemsassociatedwithnumericalcontrolbysimplyeliminatingtapeasthemediumforcarryingtheprogrammedinstructions.Indirectnumericalcontrol.machinetoolsaretied,viaadatatransmissionlink,toahostcomputer.Programsforoperatingthemachinetoolsarestoredinthehostcomputerandfedtothemachinetoolasneededviathedatatransmissionlinkage.Directnumericalcontrolrepresentedamajorstepforwardoverpunchedtapeandplastictape.However,itissubjecttothesamelimitationsasalltechnologiesthatdependonahostcomputer.Whenthelostcomputergoesdown,themachinetoolsalsoexperiencedowntime.Thisproblemledtothedevelopmentofcomputernumericalcontrol.Thedevelopmentofthemicroprocessorallowedforthedevelopmentofprogrammablelogiccontrollers(PLCs)andmicrocomputers.Thesetwotechnologiesallowedforthedevelopmentofcomputernumericalcontrol(CNC).WithCNC,eachmachinetoolhasaPLCoramicrocomputerthatservesthesamepurpose.Thisallowsprogramstobeinputandstoredateachindividualmachinetool.Italsoallowsprogramstobedevelopedoff-lineanddownloadedattheindividualmachinetool.CNCsolvedtheproblemsassociatedwithdowntimeofthehostcomputer,butitintroducedanotherknownasdatamanagement.Thesameprogrammightbeloadedontendifferentmicrocomputerswithnocommunicationamongthem.Thisproblemisintheprocessofbeingsolvedbylocalareanetworksthatconnectmicrocomputersforbetterdatamanagement.基于C8051F單片機直流電動機反饋控制系統(tǒng)的設計與研究基于單片機的嵌入式Web服務器的研究