机械外文翻译--金属切削加工.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金属切削加工金属切削加工被广泛应用于制造业。他们的特点是工件在加工前有足够的尺寸，可以将工件的最终几何形状尺寸包含在里面。不需要的材料以颗粒，切屑的方式被去除。去除切屑是获得所要求的工件几何形状，尺寸公差和表面质量的一个必要的手段。废料的数量多少不一，可能会占工件体积的从百分之几到7080不等。金属切削加工中，由于材料利用率较差，加之预计到缺乏原料和能源和成本的增加，在过去十年发展中，金属成形加工应用越来越广。但是，金属成形加工的模具的成本和设备成本仍然相当高，因此尽管金属切削加工材料浪费严重，但在许多情况下仍然是最经济的。因此金属切削加工将在今后几年保持其在制造业的重要地位。此外，金属切削加工自动化生产系统的发展比金属成形加工自动化生产系统的发展快得多。在金属切削加工中，信息的传递是通过刚性传递介质（刀具）实现的，刀具相对工件运动，机械能通过刀具作用于工件。因此，刀具的几何形状和刀具与工件运动方式决定了工件的最终形状。这个基本过程是机械过程，事实上是一个剪切和断裂相结合的过程。如前所述，多余材料在金属切削加工中是通过去刚性切削刀具去除掉的，以获得使所需的几何形状，公差和表面粗糙度的结果。属于这种加工方法的例子有：车削，钻孔，铰孔，铣削，牛头刨削，龙门刨削，拉削，磨削，珩磨和研磨。大多数切削加工或机械加工是在二维表面成型法上建立的，这意味着是必要的切割工具和工件材料得有两种相对运动。一种被称为主要运动，主要确定的切削速度和另一种被称为进给运动，它提供了切割带新的材料。车削时工件的主运动是回转运动，龙门刨床刨削时，工作台的直线运动是主运动；车削时，刀具的连续直线运动是进给运动。而在龙门刨床的刨削中，刀具的间歇运动是进给运动。切削速度：切削速度v切削刀具（切削刃上在选定的点）相对于工件的瞬时速度。切削速度车削，钻孔，铣加工可表示为V=dnm/min式中V为切削速度，单位为米/分；d是该工件将要切削部分的直径，单位是米；n工件或主轴转速，单位是转/分。但是v，d,n的意义可能有所不同，这取决于具体的运动模式。在磨削的切削速度通常是米/秒。进给量f除了主运动，当刀具或工件作进给运动时，将会导致了重复或连续的切屑被去除从而创造理想的加工表面。进给运动可以是间歇的或是连续的。进