机械加工毕业设计外文翻译微孔的加工方法.docx

机械加工毕业设计外文翻译微孔的加工方法.docx

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机械加工毕业设计外文翻译微孔的加工方法

外文原文

Optionsformicro-holemaking

Asinthemacroscale-machiningworld,holemakingisoneofthemost—ifnotthemost—frequentlyperformedoperationsformicromachining.Manyoptionsexistforhowthoseholesarecreated.Eachhasitsadvantagesandlimitations,dependingontherequiredholediameteranddepth,workpiecematerialandequipmentrequirements.Thisarticlecoversholemakingwiththrough-coolantdrillsandthosewithoutcoolantholes,plungemilling,microdrillingusingsinkerEDMsandlaserdrilling.

HelpfulHoles

Gettingcoolanttothedrilltipwhilethetooliscuttinghelpsreducetheamountofheatatthetool/workpieceinterfaceandevacuatechipsregardlessofholediameter.Butthrough-coolantcapabilityisespeciallyhelpfulwhendeep-holemicrodrillingbecausethetoolsaredelicateandpronetofailurewhenexperiencingrecuttingofchips,chippackingandtoomuchexposuretocarbide’sworstenemy—heat.

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.

Therequirementsforhowfastmicrotoolsshould