機械專業(yè)英語課件9

單詞復習：上一課回顧1Lesson9GrindingMachines

磨床

重點詞匯：2Paragraph1Grindingisachip-making(生成切屑的)metalcutting(金屬切削)process,everybitasmuchasturningormilling,exceptthatitisperformedona"micro"level(微觀范圍)wherethechipsaretoosmalltobeeasilyseenandidentified.磨削是切屑加工的金屬切削過程，除了切屑小得難以發(fā)現(xiàn)和識別以外其加工過程完全像車削（turning）和銑削(milling)。3Anotherdifferencebetweengrindinganditslarge-scale(宏觀)cousins,isthatthegrinding"tools",whichareabrasive(磨削性的)particle,arenotuniformlyshapedandorientedinthecarrier(載體),beitawheel,stone,orsomeotherdevice.磨削與形成大尺寸切屑的切削方法相比另一個最基本的不同是磨削刀具，它是磨料顆粒，在載體上形狀和方向均不一致，是砂輪形狀、石頭或其它裝置。

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Inthemetalcuttingterms,grindingisahybridbetweenturningandmilling.從金屬切削角度講，磨削是車削和銑削的綜合。

Likemilling,thegrindingtoolisinmotion,andliketurning,theworkpieceisalsonearlyalwaysmoving,althoughnotnecessarilyrotating.像銑削一樣，磨削刀具（高速）運動，像車削一樣，工件雖不一定旋轉(zhuǎn)但也總是運動的。

5Thedistinctionbetweenrotatingworkpieces,andthosemovinginalinearoroscillatingfashionundergrindingtool,butotherwisefixed,definedthemostbasicdivisioningrindingapplications.與工件旋轉(zhuǎn)的相比，在磨削刀具下面直線或往復運動的工件及其安裝方式的差別形成了磨削的各基本類型。

6Theformerisgenericallydescribedas"cylindrical”grinding,whilethelateris"surface"grinding,eventhoughbothtypescanproduceprecisionsurfaceontheworkpiecewhichisnotnecessarilyroundorflat.前者稱為外圓磨削，后者稱為平面磨削，兩種形式都能加工出粗糙工件的高精度表面。

7Paragraph3:Thefactthatboththetoolandworkpiecearenormallymovingmakesanalysisandcontrolofgrindingoperationsconsiderablymorecomplexthanisthecasewithturningormilling.工件和刀具通常都是運動的這一事實使得磨削的分析與控制與車削和銑削相比復雜得多。

8ThisisoneofthemainreasonswhymanygrindermanufacturersstilltendtodesignandbuildtheirownCNCcontrols.這也是磨削生產(chǎn)者傾向于設計和制造磨削（專用的）CNC系統(tǒng)的主要原因之一。

9Paragraph4:Manycylindricalgrindersarelaidoutonapatternsimilartoalathe.

許多外圓磨床（cylindricalgrinder）設計成與車床相似的樣式。

10Insteadofatoolholder,theyhaveamechanismtofeedthegrindingwheel,butalltheotherelements:headstock,Tailstock,waysandbedarenormallyquiterecognizabletoanyonefamiliarwithturningmachines.代替刀夾（toolholder），由一個機構(gòu)實現(xiàn)磨削砂輪的進給(feed)，而所有其它部件——主軸箱(headstock)、尾架(tailstock)、導軌(ways)和床身(bed)，通常都可以在車床上找到一個相似的部件。

11Themajordifference,however,isthattheentireworkholdingsystemusuallyismountedonasetofwayssoitcanbetraversedpastthewheelduringthegrindingoperating.主要區(qū)別在于整個工件夾持系統(tǒng)安裝在一組導軌上，因此可以相對砂輪做軸向進給。12Paragraph5Typically,inanOD(OutsideDiameter)cylindricalgrinderthewheelheadisfedradiallyintotheworkpiece,whichmayeitherremainstationaryorbereciprocatedpastit.在外圓磨床上，砂輪沿徑向?qū)ぜM給，工件或許保持靜止或許（軸向）往復運動。13Whentheworkpiecereciprocates,infeedmotionsaretypicallymadeonlyattheendofeachstroke.工件往復運動時，徑向進給只是在每個行程(stroke)的端部進行。

14Paragraph6Thethirdmajortypeofcylindricalgrinderisthe"centerless"(無心)design,whichhasnodirectanalogintheworldofturning.第三種主要形式的磨床是無心(centerless)磨床，所有車床沒有與它相似的。

15Inacenterlessgrinder(無心磨床),theworkpieceisnotheldbyeithercentersorachuck(卡盤),butissupportedona"blade"(托板)betweenthegrindingwheelanda"regulating"wheel(導輪),whichcontrolsitsrotation.在無心磨床上工件既不通過中心也不用卡盤夾持，而是放在砂輪和導輪之間的托板上，導輪控制它的旋轉(zhuǎn)。16The“regulating”wheelcontrolstherotationalspeedoftheworkpiece,servingasbothadrivingmechanism,andabrakeiftheworkpiecepicksupspeedfromthegrindingwheel.導輪控制工件的旋轉(zhuǎn)速度，它是驅(qū)動機構(gòu)，砂輪使工件的速度增大時，它又是一個制動器。

The"blade"keepstheworkinpositionbetweenthetwowheels.托板使工件在兩輪間就位。

Paragraph717Paragraph8Surfacegrinders(平面磨床)alsocomeinseveralbasicdesigns.平面磨床也有幾種基本的設計。

Probablythemostcommonhasthewheelanditsassociatedmachinerymountedaboveareciprocatingtableorotherlinermotiondevicethatholdstheworkpiece.或許最一般的是砂輪及其相關的安裝在往復運動的工作臺上或其它直線運動裝置上，用于夾持工件的機構(gòu)。

18Thewheelisfedacrosstheaxisofreciprocation,whiletheworkpiecemovesbackandforthunderit.工件來回運動時，砂輪作軸向進給。19Paragraph9Conceptually,thistypeofgrinderissimilartoaplanerinwhichthetoolholderhasbeenreplacedbythegrindingwheel.從概念上講，這種類型的磨床與（龍門）刨床(planer)相似，只是砂輪（裝置）代替了刀夾。

Thegrindingisnormallydonewiththeperipheryofthewheelonthistypeofmachine.在這種機床上，磨床是通過砂輪的圓周(periphery)來工作的。20Grindingisaprocesswithsuchabroadapplicationrangethatmanyvariationsonthesebasicdesignthemeshavebeendevelopedovertheyears,andnoattemptwillbemadetocoverthemallhereindetail.磨削是應用相當廣泛的工藝（方法），多年來開發(fā)了許多基于基本設計的工藝方法，這里不可能全部涵蓋。

Paragraph1021Jiggrinders,ultra-precisionbearingballgrinders,andawholespectrumofotherspecializedgrinderscouldeacheasilybethetopicofanarticlelongerthanthisone.坐標磨床、超高精軸承球磨床和其它所有專用磨床，每一個都很容易寫成一篇長于本文的文章。22Theprinciples,however,areessentiallyuniversalandshouldbeapplicablewithslightmodificationtovirtuallyanygrindingapplicationyoumayhave.而原理基本上是一樣的，幾乎所有磨削加工余量都很小。23Paragraph11Onetypeofspecialtygrinderthatdoesmeritbriefmentionisthetoolandcuttergrinder(工具磨床),which,asitsnameimplies,isdesignedforsharpening(刃磨)andre-sharpening(修磨)cuttingtools.一種值得一提的專用磨床是工具磨床，顧名思義，它是用來磨切削刀具的。24Thesemachinesareessentiallyhybridsincorporatingfeaturesofbothcylindricalandsurfacegrinders,whicharenecessaryforthespecializedtaskstheyarerequiredtoperform.這種磨床集外圓磨床和平面磨床于一身，對于我們要完成的一些特殊任務是非常必要的。

25Regardlessofthetypeofgrinder,themostimportantattributesitmusthavearerigidityandstability.不管哪種磨床，必須具有的最重要屬性是剛度和穩(wěn)定性。

Paragraph1226Thisisparticularlytrueincreepfeed(慢進給磨削)applications,aspecialformofgrindingwhichisperformedinasinglepass(一次走刀),withaveryhighdepthofcut,andlowworkspeed.在緩進給磨削中表現(xiàn)尤為突出，這是一種特殊的磨削方式，單走刀完成加工，切削深度很大，工件（進給）速度較低。27Properlyapplied,creepfeedgrindingcancutoverallmachiningtimebyupto50%withnolessofdimensionalorgeometricprecisionorsurfacefinishquality(表面質(zhì)量).緩進給磨削削減全部磨削加工時間高達50%，而尺寸精度、形位精度和表面質(zhì)量不降低。

28Toachievetheseresults,however,thegrindermustbedesignedspeciallyforcreepapplications,sincethetechniqueisparticularlysensitivetostaticanddynamicstabilityofthemachineandrequiresuptothreetimesthespindlepowerofacomparableconventionalgrindingprocess.為達到這一目的，磨床必須面向緩進給磨削專門設計，因為靜態(tài)或動態(tài)穩(wěn)定性對技術要求非常高，需要的主軸（砂輪）動力可達傳統(tǒng)工藝的三倍。

Paragraph1329Creepfeedalsorequiresspecialdressing(砂輪修磨)capacities,carefulattentiontowheel"hardness”,goodcoolantcontrol,andagreatdealofexperience-basedprocessknowledge.

緩進給磨削同時還要求特殊的修整能力，特別是砂輪的硬度，好的冷卻系統(tǒng)，積累起來的豐富的工藝知識。

30Creepfeed,likeallothermetalworkingtechnologies,offerssignificantadvantagesforspecificapplicationswhenproperlyapplied.像其它的金工技術一樣，緩進給磨削在一些特殊場合有很大的優(yōu)越性。

Itisnotapanacea,anditisnottheanswertoeverygrindingproblem.但它不是靈丹妙藥，也不是任何磨削問題都能解決。

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