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1、Metal-cuttingprocessMetal-cuttingprocessesareextensivelyusedinthemanufacturingindustry.Theyarecharacterizedbythefactthatthesizeoftheoriginalworkpieceissufficientlylargethatthefinalgeometrycanbecircumscribedbyit,andthattheunwantedmeterialisremovedaschips,particles,andsoon.Thechipsareanecessarymeansto
2、obtainthedesiredtolerances,andsurfaces.Theamountofscrapmayvaryfromafewpercentto70%80%ofthevolumeoftheoriginalworkmaterial.Owingtotheratherpoormaterialutilizationofthemetal-cuttingprocesses,theanticipatedscarcityofmaterialsandenergy,andincreasingcosts,thedevelopmentinthelastdecadehasbeendirectedtowar
3、danincreasingapplicationofmetal-formingprocesses.However,diecostsandthecapitalcostofmachinesremainratherhigh；consequently,metal-cuttingprocessesare,inmanycases,themosteconomical,inspiteofthehighmaterialwaste,whichonlyhasvalueasscrap.Therefore,itmustbeexpectedthatthematerialremovalprocesseswillforthe
4、nextfewyearsmaintaintheirimportantpositioninmanufacturing.Furthermore,thedevelopmentofautomatedproductionsystemshasprogressedmorerapidlyformetal-cuttingprocessesthanformetal-formingprocesses.Inmetal-cuttingprocesses,theimprintingofimformationiscarriedoutbyarigidmediumoftransfer,whichismovedrelativet
5、otheworkpiece,andthemechanicalenergyissuppliedthroughthetool.Thefinalgeometryofthetoolandthepatternofmotionsofthetoolandtheworkpiece.Thebasicprocessismechanical:actually,ashearingactioncombinedwithfracture.Asmentionedpreviously,theunwantedmaterialinmetal-cuttingprocessesisremovedbyarigidcuttingtool,
6、sothatthedesiredgeometry,tolerances,andsurfaceroughnessareobtained.Examplesofprocessesinthisgroupareturning,drilling,reaming,milling,shaping,planing,broaching,grinding,honing,andlapping.Mostofthecuttingormachiningprocessesarebasesonatwo-dimensionalsurfacecreation,whichmeansthattworelativemotionsaren
7、ecessarybetweenthecuttingtoolandtheworkmaterial.Thesemotionsaredefinedastheprimarymotion,whichmainlydeterminesthecuttingspeed,andthefeedmotion,whichprovidesthecuttingzonewithnewmaterial.Inturningtheprimarymotionisprovidedbytherotationoftheworkpiece,andinplaningitisprovidedbythetranslationofthetable；
8、inturningthefeedmotionisacontinuoustranslationofthetool,andinplaningitisanintermittenttranslationofthetool.CuttingSpeedThecuttingspeedvistheinstantaneousvelocityoftheprimarymotionofthetoolrelativetotheworkpiece(ataselectedpointonthecuttingedge).Thecuttingspeedforturning,drilling,andmillingprocessesc
9、anbeexpressedasV=dnm/minWhereviscuttingspeedinm/min,dthediameteroftheworkpiecetobecutinmeters,andntheworkpieceorspindlerotationinrev/min.thusv,d,andnmayrelatetotheworkmaterialorthetool,dependingonthespecifickinematicpattern.Ingrindingthecuttingspeedisnormallymeasuredinm/s.FeedThefeedmotionfisprovide
10、dtothetoolortheworkpieceand,whenaddedtotheprimarymotion,leadstoarepeatedorcontinuouschipremovalandthecreationofthedesiredmachinedsurface.Themotionmayproceedbystepsorcontinuously.Thefeedspeedvfisdefinedastheinstantaneousvelocityofthefeedmotionrelativetotheworkpiece(ataselectedpointonthecuttingedge)Fo
11、rturninganddrilling,thefeedfismeasuredperrevolution(mm/rev)oftheworkpieceorthetool；forplaningandshapingfismeasuredperstorke(mm/stroke)ofthetoolortheworkpiece.Inmillingthefeedismeasuredpertoothofthecuttefz(mm/touth)；thatis,fzisthedisplacementoftheworkpiecebetweenthecuttingactionoftwosuccessiveteeth。T
12、hefeedspeedvf（mm/min）ofthetableisthereforetheproductofthenumberoftheteethzofthecutter,therevolutionsperminuteofthecuttern,andthefeedpertooth(vf=nzfz).Aplanecontainingthedirectionsoftheprimarymotionandthefeedmotionisdefineastheworkingplane,sinceitcontainsthemotionsresponsibleforthecuttingaction.Depth
13、ofCut(Engagement)Inturningthedepthofcuta(sometimesalsocalledbackengagement)isthedistancethatthecuttingedgeengagesorprojectsbelowtheoriginalsurfaceoftheworkpiece.Thedepthofcutdeterminesthefinaldimensionsoftheworkpiece.Inturning,withanaxialfeed,thedepthofcutisadirectmeasureofthedecreaseinradiusofthewo
14、rkpieceandwithradialfeedthedepthofcutisequaltothedecreaseinthelengthofworkpiece.Indrilling,thedepthofcutisequaltothediameterofthedrill.Formilling,thedepthofcutisdefinedastheworkingengagementaeandistheradialengagementofthecutter.Theaxialengagement(backengagement)ofthecutteriscalledap.ChipThicknessh1i
15、ntheundeformedstateisthethicknessofthechipmeasuredperpendiculartothecuttingedgeandinaplaneperpendiculartothedirectionofcutting.Thechipthicknessaftercutting(i.e.,theactualchipthicknessh2)islargerthantheundeformedchipthickness,whichmeansthatthecuttingratioorchipthicknessratior=h1/h2isalwayslessthanuni
16、ty.ChipWidthThechipwidthbintheundeformedstateisthewidthofthechipmeasuredalongthecuttingedgeinaplaneperpendiculartothedirectionofcutting.AreafCutForsingle-pointtooloperations,theareaofcutAistheproductoftheundeformedchipthicknessh1andthechipwidthb(i.e.,A=h1b).Theareaofcutcanalsobeexpressedbythefeedfan
17、dthedepthofcutaasfollows: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(diǎn)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(gè)必要的手段。廢料的數(shù)量多
18、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(jì)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(dāng)高，因此盡管金屬切削加工材料浪費(fèi)嚴(yán)重，但在許多情況下仍然是最經(jīng)濟(jì)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(dòng)化生產(chǎn)系統(tǒng)的發(fā)展比金屬成形加工自動(dòng)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(shí)現(xiàn)的，刀具相對工件運(yùn)動(dòng)，機(jī)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(yùn)動(dòng)方式?jīng)Q定了工件的最終形狀。這個(gè)基本過程
19、是機(jī)械過程，事實(shí)上是一個(gè)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(jī)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(yùn)動(dòng)。一種被稱為主要運(yùn)動(dòng)，主要確定的切削速度和另一種被稱為進(jìn)給運(yùn)動(dòng)，它提供了切割帶新的材料。車削時(shí)工件的主運(yùn)動(dòng)是回轉(zhuǎn)運(yùn)動(dòng)，龍門刨床刨削時(shí)，工作臺的直線運(yùn)動(dòng)是主運(yùn)動(dòng)；車削時(shí)，刀具的連續(xù)直線運(yùn)動(dòng)是進(jìn)給運(yùn)動(dòng)。而在龍門刨床的刨削中，刀具的間歇運(yùn)動(dòng)是進(jìn)給運(yùn)動(dòng)。切削速度：切削速度v切削刀具（切削刃上在選定的點(diǎn)）相對于工件的瞬時(shí)速度。切削速度車削，鉆孔，銑加工可表示為V=dnm/min式中V為切削速度，單位為米/分；d是該工件將要切削部分的直徑，單位是米；n工件或主軸轉(zhuǎn)速，單位是轉(zhuǎn)/分。但是v，d,n的意義可能有所不同，這取決于具體的運(yùn)動(dòng)模式。在磨削的切削速度通常是米/秒。進(jìn)給量f除了主運(yùn)動(dòng)，當(dāng)?shù)毒呋蚬ぜ鬟M(jìn)給運(yùn)動(dòng)時(shí)，將會導(dǎo)致了重復(fù)或連續(xù)的切屑被去除從而創(chuàng)造理想的加工表面。進(jìn)給運(yùn)動(dòng)可以是間歇的或是連續(xù)的。進(jìn)
機(jī)械外文翻譯--金屬切削加工.doc
