機械外文翻譯--金屬切削加工.doc

Metal-cuttingprocessMetal-cuttingprocessesareextensivelyusedinthemanufacturingindustry.Theyarecharacterizedbythefactthatthesizeoftheoriginalworkpieceissufficientlylargethatthefinalgeometrycanbecircumscribedbyit,andthattheunwantedmeterialisremovedaschips,particles,andsoon.Thechipsareanecessarymeanstoobtainthedesiredtolerances,andsurfaces.Theamountofscrapmayvaryfromafewpercentto70%80%ofthevolumeoftheoriginalworkmaterial.Owingtotheratherpoormaterialutilizationofthemetal-cuttingprocesses,theanticipatedscarcityofmaterialsandenergy,andincreasingcosts,thedevelopmentinthelastdecadehasbeendirectedtowardanincreasingapplicationofmetal-formingprocesses.However,diecostsandthecapitalcostofmachinesremainratherhigh；consequently,metal-cuttingprocessesare,inmanycases,themosteconomical,inspiteofthehighmaterialwaste,whichonlyhasvalueasscrap.Therefore,itmustbeexpectedthatthematerialremovalprocesseswillforthenextfewyearsmaintaintheirimportantpositioninmanufacturing.Furthermore,thedevelopmentofautomatedproductionsystemshasprogressedmorerapidlyformetal-cuttingprocessesthanformetal-formingprocesses.Inmetal-cuttingprocesses,theimprintingofimformationiscarriedoutbyarigidmediumoftransfer,whichismovedrelativetotheworkpiece,andthemechanicalenergyissuppliedthroughthetool.Thefinalgeometryofthetoolandthepatternofmotionsofthetoolandtheworkpiece.Thebasicprocessismechanical:actually,ashearingactioncombinedwithfracture.Asmentionedpreviously,theunwantedmaterialinmetal-cuttingprocessesisremovedbyarigidcuttingtool,sothatthedesiredgeometry,tolerances,andsurfaceroughnessareobtained.Examplesofprocessesinthisgroupareturning,drilling,reaming,milling,shaping,planing,broaching,grinding,honing,andlapping.Mostofthecuttingormachiningprocessesarebasesonatwo-dimensionalsurfacecreation,whichmeansthattworelativemotionsarenecessarybetweenthecuttingtoolandtheworkmaterial.Thesemotionsaredefinedastheprimarymotion,whichmainlydeterminesthecuttingspeed,andthefeedmotion,whichprovidesthecuttingzonewithnewmaterial.Inturningtheprimarymotionisprovidedbytherotationoftheworkpiece,andinplaningitisprovidedbythetranslationofthetable；inturningthefeedmotionisacontinuoustranslationofthetool,andinplaningitisanintermittenttranslationofthetool.CuttingSpeedThecuttingspeedvistheinstantaneousvelocityoftheprimarymotionofthetoolrelativetotheworkpiece(ataselectedpointonthecuttingedge).Thecuttingspeedforturning,drilling,andmillingprocessescanbeexpressedasV=dnm/minWhereviscuttingspeedinm/min,dthediameteroftheworkpiecetobecutinmeters,andntheworkpieceorspindlerotationinrev/min.thusv,d,andnmayrelatetotheworkmaterialorthetool,dependingonthespecifickinematicpattern.Ingrindingthecuttingspeedisnormallymeasuredinm/s.FeedThefeedmotionfisprovidedtothetoolortheworkpieceand,whenaddedtotheprimarymotion,leadstoarepeatedorcontinuouschipremovalandthecreationofthedesiredmachinedsurface.Themotionmayproceedbystepsorcontinuously.Thefeedspeedvfisdefinedastheinstantaneousvelocityofthefeedmotionrelativetotheworkpiece(ataselectedpointonthecuttingedge)Forturninganddrilling,thefeedfismeasuredperrevolution(mm/rev)oftheworkpieceorthetool；forplaningandshapingfismeasuredperstorke(mm/stroke)ofthetoolortheworkpiece.Inmillingthefeedismeasuredpertoothofthecuttefz(mm/touth)；thatis,fzisthedisplacementoftheworkpiecebetweenthecuttingactionoftwosuccessiveteeth。Thefeedspeedvf（mm/min）ofthetableisthereforetheproductofthenumberoftheteethzofthecutter,therevolutionsperminuteofthecuttern,andthefeedpertooth(vf=nzfz).Aplanecontainingthedirectionsoftheprimarymotionandthefeedmotionisdefineastheworkingplane,sinceitcontainsthemotionsresponsibleforthecuttingaction.DepthofCut(Engagement)Inturningthedepthofcuta(sometimesalsocalledbackengagement)isthedistancethatthecuttingedgeengagesorprojectsbelowtheoriginalsurfaceoftheworkpiece.Thedepthofcutdeterminesthefinaldimensionsoftheworkpiece.Inturning,withanaxialfeed,thedepthofcutisadirectmeasureofthedecreaseinradiusoftheworkpieceandwithradialfeedthedepthofcutisequaltothedecreaseinthelengthofworkpiece.Indrilling,thedepthofcutisequaltothediameterofthedrill.Formilling,thedepthofcutisdefinedastheworkingengagementaeandistheradialengagementofthecutter.Theaxialengagement(backengagement)ofthecutteriscalledap.ChipThicknessh1intheundeformedstateisthethicknessofthechipmeasuredperpendiculartothecuttingedgeandinaplaneperpendiculartothedirectionofcutting.Thechipthicknessaftercutting(i.e.,theactualchipthicknessh2)islargerthantheundeformedchipthickness,whichmeansthatthecuttingratioorchipthicknessratior=h1/h2isalwayslessthanunity.ChipWidthThechipwidthbintheundeformedstateisthewidthofthechipmeasuredalongthecuttingedgeinaplaneperpendiculartothedirectionofcutting.AreafCutForsingle-pointtooloperations,theareaofcutAistheproductoftheundeformedchipthicknessh1andthechipwidthb(i.e.,A=h1b).Theareaofcutcanalsobeexpressedbythefeedfandthedepthofcutaasfollows:h1=fsinkandb=a/sink(27.2)wherekisthemajorcuttingedgeangle(i.e.,theanglethatthecuttingedgeformswiththeworkingplace).Consequently,theareaofcutisgivenbyA=fa金屬切削加工金屬切削加工被廣泛應(yīng)用于制造業(yè)。他們的特點是工件在加工前有足夠的尺寸，可以將工件的最終幾何形狀尺寸包含在里面。不需要的材料以顆粒，切屑的方式被去除。去除切屑是獲得所要求的工件幾何形狀，尺寸公差和表面質(zhì)量的一個必要的手段。廢料的數(shù)量多少不一，可能會占工件體積的從百分之幾到7080不等。金屬切削加工中，由于材料利用率較差，加之預(yù)計到缺乏原料和能源和成本的增加，在過去十年發(fā)展中，金屬成形加工應(yīng)用越來越廣。但是，金屬成形加工的模具的成本和設(shè)備成本仍然相當高，因此盡管金屬切削加工材料浪費嚴重，但在許多情況下仍然是最經(jīng)濟的。因此金屬切削加工將在今后幾年保持其在制造業(yè)的重要地位。此外，金屬切削加工自動化生產(chǎn)系統(tǒng)的發(fā)展比金屬成形加工自動化生產(chǎn)系統(tǒng)的發(fā)展快得多。在金屬切削加工中，信息的傳遞是通過剛性傳遞介質(zhì)（刀具）實現(xiàn)的，刀具相對工件運動，機械能通過刀具作用于工件。因此，刀具的幾何形狀和刀具與工件運動方式?jīng)Q定了工件的最終形狀。這個基本過程是機械過程，事實上是一個剪切和斷裂相結(jié)合的過程。如前所述，多余材料在金屬切削加工中是通過去剛性切削刀具去除掉的，以獲得使所需的幾何形狀，公差和表面粗糙度的結(jié)果。屬于這種加工方法的例子有：車削，鉆孔，鉸孔，銑削，牛頭刨削，龍門刨削，拉削，磨削，珩磨和研磨。大多數(shù)切削加工或機械加工是在二維表面成型法上建立的，這意味著是必要的切割工具和工件材料得有兩種相對運動。一種被稱為主要運動，主要確定的切削速度和另一種被稱為進給運動，它提供了切割帶新的材料。車削時工件的主運動