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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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