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中英文翻译MILLING铣削.doc中英文翻译MILLING铣削.doc

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编号:201311171031105441    类型:共享资源    大小:33.50KB    格式:DOC    上传时间:2013-11-17
  
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MILLING铣削Millingisabasicmachiningprocessinwhichthesurfaceisgeneratedbytheprogressiveformationandremovalofchipsofmaterialfromtheworkpieceasitisfedtoarotatingcutterinadirectionperpendiculartotheaxisofthecutter.Insomecasestheworkpieceisstationaryandthecutterisfedtothework.Inmostinstancesamultiple-toothcutterisusedsothatthemetalremovalrateishigh,andfrequentlythedesiredsurfaceisobtainedinasinglepassofthework.Thetoolusedinmillingisknownasamillingcutter.Itusuallyconsistsofacylindricalbodywhichrotatesonitsaxisandcontainsequallyspacedperipheralteeththatintermittentlyengageandcuttheworkpiece.1InsomecasestheteethextendpartwayacrossoneorbothEndsofthecylinder.Becausethemillingprincipleprovidesrapidmetalremovalandcanproducegoodsurfacefinish,itisparticularlywell-suitedformass-productionwork,andexcellentmillingmachineshavebeendevelopedforthispurpose.However,veryaccurateandversatilemillingMachinesofageneral-purposenaturealsohavebeendevelopedthatarewidelyusedinjobshopandtoolanddiework.Ashopthatisequippedwithamillingmachineandanenginelathecanmachinealmostanytypeofproductofsuitablesize.TypesofMillingOperations.Millingoperationscanbeclassifiedintotwobroadcategories,eachofwhichhasseveralvariations:1.Inperipheralmillingasurfaceisgeneratedbyteethlocatedintheperipheryofthecutterbody;thesurfaceisparallelwiththeaxisofrotationofthecutter.Bothflatandformedsurfacescanbeproducedbythismethod.Thecrosssectionoftheresultingsurfacecorrespondstotheaxialcontourofthecutter.Thisprocedureofteniscalledslabmilling.2.Infacemillingthegeneratedflatsurfaceisatrightanglestothecutteraxisandisthecombinedresultoftheactionsoftheportionsoftheteethlocatedonboththeperipheryandthefaceofthecutter.2Themajorportionofthecuttingisdonebytheperipheralportionsoftheteethwiththefaceportionsprovidingafinishingaction.ThebasicconceptsofperipheralandfacemillingareillustratedinFig.16-1.Peripheralmillingoperationsusuallyareperformedonmachineshavinghorizontalspindles,whereasfacemillingisdoneonbothhorizontal-andvertical-spindlemachines.SurfaceGenerationinMimng.SurfacescanbegeneratedinmillingbytwodistinctlydifferentmethodsdepictedinFig.16-2.Notethatinupmillingthecutterrotatesagainsithedirectionoffeedtheworkpiece,whereasindownmillingtherotationisinthesamedirectionasthefeed.AsshowninFig.16-2,themethodofchipformationisquitedifferentinthetwocases.Inupmillingthechipisverythinatthebeginning,wherethetoothfirstcontactsthework,andincreasesinthickness,becomingamaximumwherethetoothleavesthework.ThecuttertendstopushtheworkalongandliftitupwardfromTool-workrelationshiosinperipheralandfacemillingthetable.Thisactiontendstoeliminateanyeffectofloosenessinthefeedscrewandnutofthemillingmachinetableandresultsinasmoothcut.However,theactionalsotendstoloosentheworkfromtheclampingdevicesothatgreaterclampingforcersmustbeemployed.Inaddition,thesmoothnessofthegeneratedsurfacedependsgreatlyonthesharpnessofthecuttingedges.Indownmilling,maximumchipthicknesscecumclosetothepointatwhichthetoothcontactsthework.Becausetherelativemotiontendstopulltheworkpieceintothecutter,allpossibilityofloosenessinthetablefeedscrewmustbeeliminatedifdownmillingistobeused.Itshouldneverbeattemptedonmachinesthatarenotdesignedforthistypeofmilling.Inasmushasthematerialyieldsinapproximatelyatangentialdirectionattheendofthetoothengagement,thereismuchlesstendencyforthemachinedsurfacetoshowtoothmarksthanwhenupmillingisused.Anotherconsiderableadvantageofdownmillingisthatthecuttingforcetendstoholdtheworkagainstthemachinetable,permittinglowerclampingforcetobeemployed.3Thisisparticularlyadvantageouswhenmillingthinworkpieceorwhentakingheavycuts.Sometimesadisadvantageofdownmillingisthatthecutterteethstrikeagainstthesurfaceoftheworkatthebeginningofeachchip.Whentheworkpiecehasahardsurface,suchascastingsdo,thismaycausetheteethtodullrapidly.MillingCutters.Millingcutterscanbeclassifiedseveralways.Onemethodistogroupthemintotwobroadclasses,basedontoothrelief,asfollows:1.Profile-cuttershavereliefprovidedoneachtoothbygrindingasmalllandbackofthecuttingedge.Thecuttingedgemaybestraightorcurved.2.Informorcam-rehevedcuttersthecrosssectionofeachtoothisaneccentriccurvebehindthecuttingedge,thusprovidingrelief.Allsectionsoftheeccentricrelief,parallelwiththecuttingedge,musthavethesamecontourasthecuttingedge.Cuttersofthistypearesharpenedbygrindingonlythefaceoftheteeth,withthecontourofthecuttingedgethusremainingunchanged.Anotherusefulmethodofclassificationisaccordingtothemethodofmountingthecutter.Arborcuttersarethosethathaveacenterholesotheycanbemountedonanarbor.Shankcuttershaveeithertaperedorstraightintegralshank.Thosewithtaperedshankscanbemounteddirectlyinthemillingmachinespindle,whereasstraight-shankcuttersareheldinachuck.Facingcuttersusuallyareboltedtotheendofastubarbor.Thecommontypesofmillingcutters,classifiedbythissystemareasfollows:TypesofMillingCutters.Hainmillingcuttersarecylindricalordisk-shaped,havingstraightorhelicalteethontheperiphery.Theyareusedformillingflatsurfaces.Thistypeofoperationiscalledplainorslabmilling.Eachtoothinahelicalcutterengagestheworkgradually,andusuallymorethanonetoothcutsatagiventime.Thisreducesshockandchatteringtendenciesandpromotesasmoothersurface.Consequently,thistypeofcutterusuallyispreferredoveronewithstraightteeth.Sidemillingcuttersaresimilartoplainmillingcuttersexceptthattheteethextendradiallypartwayacrossoneorbothendsofthecylindertowardthe:center.Theteethmaybeeitherstraightorhelical.Frequentlythesecuttersarerelativelynarrow,beingdisklikeinshape.Twoormoresidemillingcuttersoftenarespacedonanarbortomakesimultaneous,parallelcuts,inanoperationcalledstraddlemilling.Interlockingslottingcuttersconsistoftwocutterssimilartosidemills,butmadetooperateasaunitformillingslots.Thetwocuttersareadjustedtothedesiredwidthbyinsertingshimsbetweenthem.Staggered-toothmillingcuttersarenarrowcylindricalcuttershavingstaggeredteeth,andwithalternateteethhavingoppositehelixangles.Theyaregroundtocutonlyontheperiphery,buteachtoothalsohaschipclearancegroundontheprotrudingside.Thesecuttershaveafreecuttingactionthatmakesthemparticnlarlyeffectiveinmillingdeepslots.Metal-slittingsawsarethin,plainmillingcutters,usuallyfrom1/32to3/16inchthick,whichhavetheirsidesslightly"dished"toprovideclearanceandpreventbinding.Theyusuallyhavemoreteethperinchofdiameterthanordinaryplainmillingcuttersandareusedformillingdeep,narrowslotsandforcutting-offoperations.数控铣削铣削是机械加工的一个基础方法。在这一加工过程中,当工件沿垂直于旋转刀具轴线方向进给时,在工件上形成并去除切屑从而逐渐地铣出表面。有时候,工件是固定的,而刀具处于进给状态。在大多数情况下,使用多齿刀具,金属切削量大,只需一次铣削就可以获得所期望的表面。在铣削加工中使用的刀具称做铣刀。它通常是一个绕其轴线旋转并且周边带有同间距齿的圆柱体,铣刀齿间歇性接触并切削工件。在某些情况下,铣刀上的刀齿会高出圆柱体的一端或两端。由于铣削切削金属速度很快,并且能产生良好的表面光洁度,故特别适合大规模生产加工。为了实现这一目的,已经制造出了质量一流的铣床。然而在机修车间和工具模具加工中也已经广泛地使用了非常精确的多功能通用的铣床。车间里拥有一台铣床和一台普通车床就能加工出具有适合尺寸的各种产品。铣削操作类型:铣削操作可以分成两大种类,每一类又有多种类型。1.圆周铣削在圆周铣削中,使用的铣刀刀齿固定在刀体的圆周面上,工件铣削表面与旋转刀具轴线平行,从而加工表面。使用这种方法可以加工出平面和成型表面,加工中表面横截面与刀具的轴向外轮廓相一致。这种加工过程常被称为平面铣削。
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