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外文翻译--微孔的加工方法.doc

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外文翻译--微孔的加工方法.doc

英语翻译OptionsformicroholemakingAsinthemacroscalemachiningworld,holemakingisoneofthemostifnotthemostfrequentlyperformedoperationsformicromachining.Manyoptionsexistforhowthoseholesarecreated.Eachhasitsadvantagesandlimitations,dependingontherequiredholediameteranddepth,workpiecematerialandequipmentrequirements.Thisarticlecoversholemakingwiththroughcoolantdrillsandthosewithoutcoolantholes,plungemilling,microdrillingusingsinkerEDMsandlaserdrilling.HelpfulHolesGettingcoolanttothedrilltipwhilethetooliscuttinghelpsreducetheamountofheatatthetool/workpieceinterfaceandevacuatechipsregardlessofholediameter.Butthroughcoolantcapabilityisespeciallyhelpfulwhendeepholemicrodrillingbecausethetoolsaredelicateandpronetofailurewhenexperiencingrecuttingofchips,chippackingandtoomuchexposuretocarbidesworstenemyheat.Whenapplyingfloodcoolant,thedrillitselfblocksaccesstothecuttingaction.Somewhereabout3to5diametersdeep,thecoolanthastroublegettingdowntothetip,saidJeffDavis,vicepresidentofengineeringforHarveyToolCo.,Rowley,Mass.Itbecomeswisetouseacoolantfeddrillatthatpoint.Topreventthosetinycoolantholesfrombecomingcloggedwithdebris,Davisalsorecommendsa5μmorfinercoolantfilter.Anotherrecommendationistomachineapilot,orguide,holetopreventthetoolfromwanderingontopoftheworkpieceandaidinproducingastraighthole.Whenapplyingapilotdrill,itsimportanttoselectonewithanincludedangleonitspointthatsequaltoorlargerthantheincludedangleonthethroughcoolantdrillthatfollows.Thepilotdrillsdiametershouldalsobeslightlylarger.Forexample,ifthepilotdrillhasa120°includedangleandasmallerdiameterthanathroughcoolantdrillwitha140°includedangle,thenyourecatchingthecoolantfeddrillscornersandknockingthosecornersoff,Davissaid,whichdamagesthedrill.LubriciousChillTofurtheraidchipevacuation,Davisrecommendsapplyinganoilbasedmetalworkingfluidinsteadofawaterbasedcoolantbecauseoilprovidesgreaterlubricity.Butifashopprefersusingcoolant,thefluidshouldincludeEPextremepressureadditivestoincreaselubricityandminimizefoaming.Ifyouvegotalotoffoam,Davisnoted,thechipsarentbeingpulledoutthewaytheyaresupposedtobe.Headdedthatanotherwaytoenhanceatoolsslipperinesswhileextendingitslifeiswithacoating,suchastitaniumaluminumnitride.TiAlNhasahighhardnessandisaneffectivecoatingforreducingheatsimpactwhendrillingdifficulttomachinematerials,likestainlesssteel.DavidBurton,generalmanagerofPerformanceMicroTool,Janesville,Wis.,disagreeswiththeideaofcoatingmicrotoolsonthesmallerendofthespectrum.Coatingsontoolsbelow0.020typicallyhaveaeffectoneverymachiningaspect,fromthequalityoftheinitialcuttotoollife,hesaid.Thatsbecausecoatingsarenotthinenoughandnegativelyaltertherakeandreliefangleswhenappliedtotinytools.However,workcontinuesonthedevelopmentofthinnercoatings,andBurtonindicatedthatPerformanceMicroTool,whichproducesmicroendmillsandmicroroutersandresellsmicrodrills,isworkingonaprojectwithotherstocreateasubmicronthicknesscoating.Wereprobably6monthsto1yearfromtestingitinthemarket,Burtonsaid.ThemicrodrillsPerformanceoffersarebasicallycircuitboarddrills,whicharealsoeffectiveforcuttingmetal.Allthetoolsarewithoutthroughcoolantcapability.Ihadacustomerdrilla0.004dia.holeinstainlesssteel,andhewasamazedhecoulddoitwithacircuitboarddrill,Burtonnoted,addingthatpeckingandrunningatahighspindlespeedincreasethedrillseffectiveness.TherequirementsforhowfastmicrotoolsshouldrotatedependonthetypeofCNCmachinesashopusesandthetooldiameter,withhigherspeedsneededasthediameterdecreases.NoteTheequationforcuttingspeedissfmtooldiameter0.26spindlespeed.Althoughrelativelylow,5,000rpmhasbeenusedsuccessfullybyBurtonscustomers.Werecommendthatourcustomersfindthehighestrpmatthelowestpossiblevibrationthesweetspot,hesaid.Inadditiontominimizingvibration,aconstantandadequatechiploadisrequiredtopenetratetheworkpiecewhileexertinglowcuttingforcesandtoallowtheraketoremovetheappropriateamountofmaterial.Ifthedrilltakestoolightofachipload,therakefacewearsquickly,becomingnegative,andtoollifesuffers.Thisapproachisoftentemptingwhendrillingwithdelicatetools.Ifthecustomerdecideshewantstobabythetool,hetakesalighterchipload,Burtonsaid,and,typically,thecuttingedgewearsmuchquickerandcreatesaradiuswherethelandofthatradiusiswiderthanthechipbeingcut.Heendsupusingitasagrindingtool,tryingtobumpmaterialaway.Fortoolslargerthan0.001,Burtonconsidersachiploadunder0.0001tobebabying.Ifthedrilldoesntsnap,prematurewearcanresultinabysmaltoollife.Toomuchrunoutcanalsobedestructive,buthowmuchisdebatable.BurtonpointedoutthatPerformancepurposelydesignedamachinetohave0.0003TIRtoconductinhouse,worstcasemillingscenarios,addingthatthecompanyisstillabletomilla0.004wideslotdayinanddayout.HeaddedYouwouldthinkwith0.0003runoutandachiploadathirdthat,say,0.0001to0.00015,thetoolwouldbreakimmediatelybecauseoneflutewouldbetakingtheentireloadandthenthebackendoftheflutewouldberubbing.Whendrilling,heindicatedthatupto0.0003TIRshouldbeacceptablebecauseoncethedrillisinsidethehole,thecuttingedgesontheendofthedrillcontinuecuttingwhilethenoncuttinglandsontheODguidethetoolinthesamedirection.Minimizingrunoutbecomesmorecriticalasthedepthtodiameterratioincreases.Thisisbecausetheflutesarenotabletoabsorbasmuchdeflectionastheybecomemoreengagedintheworkpiece.Ultimately,toomuchrunoutcausesthetoolshanktoorbitaroundthetoolscenterwhilethetooltipisheldsteady,creatingastresspointwherethetoolwilleventuallybreak.TakingaPlungeAlthoughstandardmicrodrillsarentgenerallyavailablebelow0.002,microendmillsthatcanbeusedtoplungeaholeare.Whenpeoplewanttodrillsmallerthanthat,theyuseourendmillsandareprettysuccessful,Burtonsaid.However,theholescantbeverydeepbecausethetoolsdonthavelongaspect,ordepthtodiameter,ratios.Therefore,a0.001dia.endmillmightbeabletoonlymakeaholeupto0.020deepwhereasadrillofthesamesizecangodeeperbecauseitsdesignedtoplacetheloadonitstipwhendrilling.Thistransfersthepressureintotheshank,whichabsorbsit.Performanceoffersendmillsassmallas5microns0.0002butisntkeenonincreasingthatlinessales.Whenpeopletrytobuythem,Iveryseriouslytrytotalkthemoutofitbecausewedontlikemakingthem,Burtonsaid.Partoftheproblemwithtoolsthatsmallisthecarbidegrainsnotonlyneedtobesubmicroninsizebutthesizealsoneedstobeconsistent,inpartbecausesuchatooliscomprisedoffewergrains.The5micronendmillprobablyhas10grainsholdingthecoretogether,Burtonnoted.Headdedthathehasseencarbidepowdercontaining0.2microngrains,whichisabouthalfthesizeofwhatscommerciallyavailable,butitalsocontainedgrainsmeasuring0.5and0.6microns.Itjustdoesnthelptohavesmallgrainsiftheyrenotuniform.MicrovaporizationElectricaldischargemachiningusingasinkerEDMisanothermicroholemakingoption.Unlike,whichcreatesmallholesforthreadingwirethroughtheworkpiecewhenwireEDMing,EDMsforproducingmicroholesareconsiderablymoresophisticated,accurateand,ofcourse,expensive.Forproducingdeepmicroholes,atubeisappliedastheelectrode.ForEDMingsmallerbutshallowerholes,asolidelectrodewire,orrod,isneeded.Wetrytousetubesasmuchaspossible,saidJeffKiszonas,EDMproductmanagerforMakinoInc.,AuburnHills,Mich.Butatsomepoint,nobodycanmakeatubebelowacertaindiameter.Headdedthatsomesuppliersoffertubesdownto0.003indiameterformakingholesassmallas0.0038.Thetubesflushingholeenablescreatingaholewithahighdepthtodiameterratioandhelpstoevacuatedebrisfromthebottomoftheholeduringmachining.OnesuchsinkerEDMforproducingholesassmallas0.0004411μmisMakinosEdge2sinkerEDMwithfineholeoption.InJapan,themachinetoolbuilderrecentlyproducedeightsuchholesin2minutesand40secondsthrough0.0010thicktungstencarbideattheholelocations.Theelectrodewasasilvertungstenrod0.00020smallerthantheholebeingproduced,toaccountforsparkactivityinthegap.Whenproducingholesofthatsize,therod,whilerotating,isdressedwithachargedEDMwire.ThefineholeoptionincludesaWaxisattachment,whichholdsadiethatguidestheelectrode,aswellasamiddleguidethatpreventstheelectrodefrombendingorwobblingasitspins.Withtheoption,themachineisappropriatefordrillingholediameterslessthan0.005.AnothersinkerEDMformicroholemakingistheMitsubishiVA10withafineholejigattachmenttochuckandguidethefinewireappliedtoerodethematerial.ItsastandardEDM,butwiththatattachmentfixedtothemachine,wecandomicroholedrilling,saidDennisPowderly,sinkerEDMproductmanagerforMCMachinerySystemsInc.,WoodDale,Ill.HeaddedthattheEDMisalsoabletocreateholesdownto0.0004usingawirethatrotatesatupto2,000rpm.TurntoTungstenEDMingistypicallyaslowprocess,andthatholdstruewhenitisusedformicrodrilling.Itsveryslow,andthefinerthedetails,thesloweritis,said,presidentandownerofOptimationInc.TheMidvale,Utah,companybuildsProfile24PiezoEDMsformicromachiningandalsoperformsmicroEDMingonacontractmachiningbasis.Optimationproducestungstenelectrodesusingareversepolarityprocessandmachinesandringlapsthemtoassmallas10μmindiameterwith0.000020roundness.Applyinga10μmdia.electrodeproducesaholeabout10.5μmto11μmindiameter,andblindholesarepossiblewiththecompanysEDM.Theworkpiecethicknessforthesmallestholesisupto0.002,andthethicknesscanbeupto0.04for50μmholes.Muchofthecompanyscontractwork,whichisprovidedatashoprateof100perhour,involvesmicroEDMingexoticmetals,suchasgoldandplatinumforXrayapertures,stainlesssteelforopticalapplicationsandtantalumandtungstenfortheelectronbeamindustry.JorgensensaidtheprocessisalsoappropriateforEDMingpartiallyelectricallyconductivematerials,suchasPCD.Thecustomernormallydoesntcaretoomuchaboutthecost,hesaid.Wevedonepartswheretheres20,000intimeandmaterialinvolved,andyoucanputthewholejobunderneathafingernail.Wedoeverythingunderamicroscope.LightCuttingBesidescarbideandtungsten,lightisanappropriatetoolmaterialformicroholemaking.Althoughmostlaserdrillingisperformedintheinfraredspectrum,theSuperPulsetechnologyfromTheExOneCo.,Irwin,Pa.,usesagreenlaserbeam,saidRandyGilmore,thecompanysdirectoroflasertechnologies.Unlikethefemtosecondvariety,SuperPulseisananosecondlaser,

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