机械类毕业设计外文翻译微孔的加工方法Word文件下载.docx

机械类毕业设计外文翻译微孔的加工方法Word文件下载.docx

《机械类毕业设计外文翻译微孔的加工方法Word文件下载.docx》由会员分享，可在线阅读，更多相关《机械类毕业设计外文翻译微孔的加工方法Word文件下载.docx（10页珍藏版）》请在冰豆网上搜索。

Whenapplyingfloodcoolant,thedrillitselfblocksaccesstothecuttingaction.“Somewhereabout3to5diametersdeep,thecoolanthastroublegettingdowntothetip,”saidJeffDavis,vicepresidentofengineeringforHarveyToolCo.,Rowley,Mass.“Itbecomeswisetouseacoolant-feddrillatthatpoint.”

Inaddition,floodcoolantcancausemoreharmthangoodwhenmicroholemaking.“Thepressurefromthefloodcoolantcansometimessnapfragiledrillsastheyenterthepart,”Davissaid.

Thetoolmakeroffersalineofthrough-coolantdrillswithdiametersfrom0.039"

to0.125"

thatareabletoproduceholesupto12diametersdeep,aswellasmicrodrillswithoutcoolantholesfrom0.002"

to0.020"

.

Havingthrough-coolantcapacityisn’tenough,though.Coolantneedstoflowataratethatenablesittoclearthechipsoutofthehole.Davisrecommends,ataminimum,600to800psiofcoolantpressure.“Itworksmuchbetterifyouhavehigherpressurethanthat,”headded.

Topreventthosetinycoolantholesfrombecomingcloggedwithdebris,Davisalsorecommendsa5μmorfinercoolantfilter.

Anotherrecommendationistomachineapilot,orguide,holetopreventthetoolfromwanderingontopoftheworkpieceandaidinproducingastraighthole.Whenapplyingapilotdrill,it’simportanttoselectonewithanincludedangleonitspointthat’sequaltoorlargerthantheincludedangleonthethrough-coolantdrillthatfollows.Thepilotdrill’sdiametershouldalsobeslightlylarger.Forexample,ifthepilotdrillhasa120°

includedangleandasmallerdiameterthanathrough-coolantdrillwitha140°

includedangle,“thenyou’recatchingthecoolant-feddrill’scornersandknockingthosecornersoff,”Davissaid,whichdamagesthedrill.

Althoughnotmandatory,peckingisagoodpracticewhenmicrodrillingdeepholes.Davissuggestsapeckingcyclethatis30to50percentofthediameterperpeckdepth,dependingontheworkpiecematerial.Thisclearsthechips,preventingthemfrompackingintheflutevalleys.

LubriciousChill

Tofurtheraidchipevacuation,Davisrecommendsapplyinganoil-basedmetalworkingfluidinsteadofawaterbasedcoolantbecauseoilprovidesgreaterlubricity.Butifashopprefersusingcoolant,thefluidshouldincludeEP（extremepressure）additivestoincreaselubricityandminimizefoaming.“Ifyou’vegotalotoffoam,”Davisnoted,“thechipsaren’tbeingpulledoutthewaytheyaresupposedtobe.”

Headdedthatanotherwaytoenhanceatool’sslipperinesswhileextendingitslifeiswithacoating,suchastitaniumaluminumnitride.TiAlNhasahighhardnessandisaneffectivecoatingforreducingheat’simpactwhendrillingdifficult-to-machinematerials,likestainlesssteel.

DavidBurton,generalmanagerofPerformanceMicroTool,Janesville,Wis.,disagreeswiththeideaofcoatingmicrotoolsonthesmallerendofthespectrum.“Coatingsontoolsbelow0.020"

typicallyhaveanegativeeffectoneverymachiningaspect,fromthequalityoftheinitialcuttotoollife,”hesaid.That’sbecausecoatingsarenotthinenoughandnegativelyaltertherakeandreliefangleswhenappliedtotinytools.

However,workcontinuesonthedevelopmentofthinnercoatings,andBurtonindicatedthatPerformanceMicroTool,whichproducesmicroendmillsandmicroroutersandresellsmicrodrills,isworkingonaprojectwithotherstocreateasubmicron-thicknesscoating.“We’reprobably6monthsto1yearfromtestingitinthemarket,”Burtonsaid.

ThemicrodrillsPerformanceoffersarebasicallycircuit-boarddrills,whicharealsoeffectiveforcuttingmetal.Allthetoolsarewithoutthrough-coolantcapability.“Ihadacustomerdrilla0.004"

-dia.holeinstainlesssteel,andhewasamazedhecoulddoitwithacircuit-boarddrill,”Burtonnoted,addingthatpeckingandrunningatahighspindlespeedincreasethedrill’seffectiveness.

TherequirementsforhowfastmicrotoolsshouldrotatedependonthetypeofCNCmachinesashopusesandthetooldiameter,withhigherspeedsneededasthediameterdecreases.（Note:

Theequationforcuttingspeedissfm=tooldiameter×

0.26×

spindlespeed.）

Althoughrelativelylow,5,000rpmhasbeenusedsuccessfullybyBurton’scustomers.“Werecommendthatourcustomersfindthehighestrpmatthelowestpossiblevibration—thesweetspot,”hesaid.

Inadditiontominimizingvibration,aconstantandadequatechiploadisrequiredtopenetratetheworkpiecewhileexertinglowcuttingforcesandtoallowtheraketoremovetheappropriateamountofmaterial.Ifthedrilltakestoolightofachipload,therakefacewearsquickly,becomingnegative,andtoollifesuffers.Thisapproachisoftentemptingwhendrillingwithdelicatetools.

“Ifthecustomerdecideshewantstobabythetool,hetakesalighterchipload,”Burtonsaid,“and,typically,thecuttingedgewearsmuchquickerandcreatesaradiuswherethelandofthatradiusiswiderthanthechipbeingcut.Heendsupusingitasagrindingtool,tryingtobumpmaterialaway.”Fortoolslargerthan0.001"

Burtonconsidersachiploadunder0.0001"

tobe“babying.”Ifthedrilldoesn’tsnap,prematurewearcanresultinabysmaltoollife.

Toomuchrunoutcanalsobedestructive,buthowmuchisdebatable.BurtonpointedoutthatPerformancepurposelydesignedamachinetohave0.0003"

TIRtoconductin-house,worst-casemillingscenarios,addingthatthecompanyisstillabletomilla0.004"

-wideslot“dayinanddayout.”

Headded:

“Youwouldthinkwith0.0003"

runoutandachiploadathirdthat,say,0.0001"

to0.00015"

thetoolwouldbreakimmediatelybecauseoneflutewouldbetakingtheentireloadandthenthebackendoftheflutewouldberubbing.

Whendrilling,heindicatedthatupto0.0003"

TIRshouldbeacceptablebecauseoncethedrillisinsidethehole,thecuttingedgesontheendofthedrillcontinuecuttingwhilethenoncuttinglandsontheODguidethetoolinthesamedirection.Minimizingrunoutbecomesmorecriticalasthedepth-to-diameterratioincreases.Thisisbecausetheflutesarenotabletoabsorbasmuchdeflectionastheybecomemoreengagedintheworkpiece.Ultimately,toomuchrunoutcausesthetoolshanktoorbitaroundthetool’scenterwhilethetooltipisheldsteady,creatingastresspointwherethetoolwilleventuallybreak.

TakingaPlunge

Althoughstandardmicrodrillsaren’tgenerallyavailablebelow0.002"

microendmillsthatcanbeusedto“plunge”aholeare.“Whenpeoplewanttodrillsmallerthanthat,theyuseourendmillsandareprettysuccessful,”Burtonsaid.However,theholescan’tbeverydeepbecausethetoolsdon’thavelongaspect,ordepth-to-diameter,ratios.Therefore,a0.001"

-dia.endmillmightbeabletoonlymakeaholeupto0.020"

deepwhereasadrillofthesamesizecangodeeperbecauseit’sdesignedtoplacetheloadonitstipwhendrilling.Thistransfersthepressureintotheshank,whichabsorbsit.

Performanceoffersendmillsassmallas5microns（0.0002"

）butisn’tkeenonincreasingthatline’ssales.“Whenpeopletrytobuythem,Iveryseriouslytrytotalkthemoutofitbecausewedon’tlikemakingthem,”Burtonsaid.Partoftheproblemwithtoolsthatsmallisthecarbidegrainsnotonlyneedtobesubmicroninsizebutthesizealsoneedstobeconsistent,inpartbecausesuchatooliscomprisedoffewergrains.“The5-micronendmillprobablyhas10grainsholdingthecoretogether,”Burtonnoted.

Headdedthathehasseencarbidepowdercontaining0.2-microngrains,whichisabouthalfthesizeofwhat’scommerciallyavailable,butitalsocontainedgrainsmeasuring0.5and0.6microns.“Itjustdoesn’thelptohavesmallgrainsifthey’renotuniform.”

Microvaporization

ElectricaldischargemachiningusingasinkerEDMisanothermicro-holemakingoption.Unlike,whichcreatesmallholesforthreadingwirethroughtheworkpiecewhenwireEDMing,EDMsforproducingmicroholesareconsiderablymoresophisticated,accurateand,ofcourse,expensive.

Forproducingdeepmicroholes,atubeisappliedastheelectrode.ForEDMingsmallerbutshallowerholes,asolidelectrodewire,orrod,isneeded.“Wetrytousetubesasmuchaspossible,”saidJeffKiszonas,EDMproductmanagerforMakinoInc.,AuburnHills,Mich.“Butatsomepoint,nobodycanmakeatubebelowacertaindiameter.”Headdedthatsomesuppliersoffertubesdownto0.003"

indiameterformakingholesassmallas0.0038"

.Thetube’sflushingholeenablescreatingaholewithahighdepth-to-diameterratioandhelpstoevacuatedebrisfromthebottomoftheholeduringmachining.

OnesuchsinkerEDMforproducingholesassmallas0.00044"

（11μm）isMakino’sEdge2sinkerEDMwithfine-holeoption.InJapan,themachinetoolbuilderrecentlyproducedeightsuchholesin2minutesand40secondsthrough0.0