機(jī)械類畢業(yè)設(shè)計(jì)外文翻譯

哈爾濱理工大學(xué)2008屆本科生畢業(yè)設(shè)計(jì)（論文）外文翻譯外文原文Optionsformicro-holemakingAsinthemacroscale-machiningworld,holemakingisoneofthemost—ifnotthemost—frequentlyperformedoperationsformicromachining.Manyoptionsexistforhowthoseholesarecreated.Eachhasitsadvantagesandlimitations,dependingontherequiredholediameteranddepth,workpiecematerialandequipmentrequirements.Thisarticlecoversholemakingwiththrough-coolantdrillsandthosewithoutcoolantholes,plungemilling,microdrillingusingsinkerEDMsandlaserdrilling.HelpfulHolesGettingcoolanttothedrilltipwhilethetooliscuttinghelpsreducetheamountofheatatthetool/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.LubriciousChillTofurtheraidchipevacuation,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×spindleEDM,butwiththatattachmentfixedtothemachine,wecandomicroholedrilling,”saidDennisPowderly,sinkerEDMproductmanagerforMCMachinerySystemsInc.,WoodDale,Ill.HeaddedthattheEDMisalsoabletocreateholesdownto0.0004"usingawirethatrotatesatupto2,000rpm.TurntoTungstenEDMingistypicallyaslowprocess,andthatholdstruewhenitisusedformicrodrilling.“It’sveryslow,andthefinerthedetails,thesloweritis,”said,presidentandownerofOptimationInc.TheMidvale,Utah,companybuildsProfile24PiezoEDMsformicromachiningandalsoperformsmicroEDMingonacontract-machiningbasis.Optimationproducestungstenelectrodesusingareverse-polarityprocessandmachinesandring-lapsthemtoassmallas10μmindiameterwith0.000020"roundness.Applyinga10μm-dia.electrodeproducesaholeabout10.5μmto11μmindiameter,andblind-holesarepossiblewiththecompany’sEDM.Theworkpiecethicknessforthesmallestholesisupto0.002",andthethicknesscanbeupto0.04"for50μmholes.AfterworkingwithlasersandthenwithaformerEDMbuildertofindabetterwaytoproduceprecisemicroholes,JorgensendecidedthebestapproachwasDIY.“Weliterallystartedwithacleansheetofpaperanddidalltheelectronics,allthesoftwareandthewholemachinefromscratch,”hesaid.Includingthesoftware,themachinecostsintheneighborhoodof$180,000to$200,000.Muchofthecompany’scontractwork,whichisprovidedatashoprateof$100perhour,involvesmicroEDMingexoticmetals,suchasgoldandplatinumforX-rayapertures,stainlesssteelforopticalapplicationsandtantalumandtungstenfortheelectron-beamindustry.JorgensensaidtheprocessisalsoappropriateforEDMingpartiallyelectricallyconductivematerials,suchasPCD.“Thecustomernormallydoesn’tcaretoomuchaboutthecost,”hesaid.“We’vedonepartswherethere’s$20,000[intimeandmaterial]involved,andyoucanputthewholejobunderneathafingernail.Wedoeverythingunderamicroscope.”LightCuttingBesidescarbideandtungsten,lightisanappropriate“toolmaterial”formicro-holemaking.Althoughmostlaserdrillingisperformedintheinfraredspectrum,theSuperPulsetechnologyfromTheExOneCo.,Irwin,Pa.,usesagreenlaserbeam,saidRandyGilmore,thecompany’sdirectoroflasertechnologies.Unlikethefemtosecondvariety,Super-Pulseisananosecondlaser,anditsgreenlightoperatesatthe532-nanometerwavelength.Thetechnologyprovideslaserpulsesof4to5nanosecondsinduration,andthosepulsesaresentinpairswithadelayof50to100nanosecondsbetweenindividualpulses.Thebenefitsofthisapproacharetwofold.“Itgreatlyenhancesmaterialremovalcomparedtoothernanosecondlasers,”Gilmoresaid,“andgreatlyreducestheamountofthermaldamagedonetotheworkpiecematerial”becauseofthepulses’shortduration.TheminimumdiameterproducedwiththeSuperPulselaseris45microns,butoneofthemostcommonapplicationsisforproducing90μmto110μmholesindieselinjectornozzlesmadeof1mm-thickHseriessteel.Gilmorenotedthatthoseholeswillneedtobeinthe50μmto70μmrangeasemissionstandardstightenbecausesmallerholesininjectornozzlesatomizedieselfuelbetterformoreefficientburning.Inaddition,thetechnologycanproducenegativelytaperedholes,withasmallerentrancethanexitdiameter,topromotebetterfuelflow.Anothercommonapplicationisdrillingholesinaircraftturbinebladesforcooling.Althoughtheturbinematerialmightonlybe1.5mmto2mmthick,Gilmoreexplainedthattheholesaredrilledata25°entryanglesotheair,asitcomesoutoftheholes,hugstheairfoilsurfaceanddragstheheataway.Thatmeanstheholetraversesupto5mmofmaterial.“Temperatureiseverythinginaturbine”hesaid,“becauseinanaircraftengine,thehotteryoucanruntheturbine,thebetterthefueleconomyandthemorethrustyouget.”Tofurtherenhancethetechnology’scompetitiveness,ExOnedevelopedapatent-pendingmaterialthatisinjectedintoahollow-bodycomponenttoblockthelaserbeamandpreventback-wallstrikesafteritcreatestheneededhole.Afterlasermachining,theenduserremovesthematerialwithoutleavingremnants.“Oneofthebugaboosingettinglasersacceptedinthedieselinjectorcommunityisthatlighthasanastyhabitofcontinuingtotraveluntilitmeetsanotherobject,”Gilmoresaid.“Inadieselinjectornozzle,thatdamagestheinteriorsurfaceoftheoppositewall.”Althoughthe$650,000to$800,000priceforaSuper-Pulselaserishigherthanamicro-holemakingEDM,Gilmorenotedthatlaserdrillingdoesn’trequireelectrodes.“Alasersystemisusinglighttomakeholes,”hesaid,“soitdoesn’thaveaconsumable.”Dependingontheapplication,mechanicaldrillingandplungemilling,EDMingandlasermachiningallhavetheirplaceintheexpandingmicromachininguniverse.“Peoplewantmorepackedintosmallerspaces,”saidMakino’sKiszonas.中文翻譯微孔的加工方法正如宏觀加工一樣，在微觀加工中孔的加工也許也是最常用的加工之一?？椎募庸し椒ㄓ泻芏喾N，每一種都有其優(yōu)點(diǎn)和缺陷，這主要取決于孔的直徑、深度、工件材料和設(shè)備要求。這篇文章主要介紹了內(nèi)冷卻鉆頭鉆孔、無冷卻鉆孔、插銑、電火花以及激光加工微孔的幾種方法。易于孔加工的操作無論孔有多大，在加工時(shí)將冷卻液導(dǎo)入到刀尖，這都有助于排屑并能降低刀具和工件表面產(chǎn)生的摩擦熱。尤其是在加工深細(xì)孔時(shí)，有無冷卻對(duì)加工的影響更大，因?yàn)樯罴?xì)孔加工的刀具比較脆弱，再加上刀具對(duì)切屑的二次切削和切屑的堆積會(huì)積累大量的熱，而熱量是碳化物刀具的主要“天敵”，它會(huì)加快刀具的失效速度。當(dāng)使用外冷卻液時(shí)，刀具本身會(huì)阻止切削液進(jìn)入切削加工位置。“也就是到3-5倍的直徑深度后切削液就會(huì)很難流入到刀尖?！备惫S工具有限公的副總工程師杰夫戴維斯說，“這時(shí)，就應(yīng)該選用帶有內(nèi)冷的鉆頭?！绷硗?，在加工小孔時(shí)采用外冷卻液的冷卻方式產(chǎn)生的利要大于弊，“當(dāng)鉆頭進(jìn)入工件時(shí)，已經(jīng)流入孔的冷卻液產(chǎn)生的壓力有時(shí)會(huì)繳壞鉆頭?！贝骶S斯說。刀具生產(chǎn)商提供的標(biāo)準(zhǔn)鉆頭的直徑從0.039到0.125英寸，能加工深度小于12倍直徑的深孔，同時(shí)提供直徑從0.002到0.020英寸的不帶內(nèi)冷的鉆頭。盡管有內(nèi)冷能力，但還是不夠的，冷卻液還需要一定的流動(dòng)速度從而能夠?qū)⑶行记宄隹淄?。戴維斯強(qiáng)調(diào)，冷卻液的最低壓力應(yīng)為600-800磅/平方英寸，“加工狀況還會(huì)隨著所施壓力的增加而提高?！彼a(bǔ)充道。為了防止這些冷卻液通口被雜物堵塞，戴維斯還推薦在鉆頭上加一5μm孔徑或更加精密的冷卻液濾清器。另外，他還推薦在加工孔時(shí)有必要在工件的上方先加工一個(gè)定心或?qū)蚩?，以防止刀具偏斜，并有助于保證所加工孔的垂直度。當(dāng)選用定心鉆時(shí)，應(yīng)使選擇的定心鉆刀尖上的坡口角小于等于其后內(nèi)冷鉆的破口角。定心鉆的直徑還要稍微大一些。例如，如果定心鉆的坡口角為120°，內(nèi)冷卻鉆頭的坡口角為140°，并且定心鉆的直徑小于內(nèi)冷卻鉆的直徑，“在加工時(shí)內(nèi)冷卻鉆的拐角處會(huì)與定心孔干涉而容易脫落，”戴維斯說，“這將導(dǎo)致鉆頭損壞?！彪m然沒加強(qiáng)調(diào)，但是加工細(xì)深孔時(shí)，啄式進(jìn)給是一種很好的加工方式。戴維斯建議，根據(jù)工件的材料的不同，每次啄式進(jìn)給的深度最好為孔徑的30%—50%。這種加工方式便于排出切屑，使切屑不在加工的孔中堆積。潤滑及冷卻為了更加有助于排屑，戴維斯推薦在金屬加工中用油基金屬切削液代替水基冷卻液，因?yàn)橛途哂休^高的潤滑效果。但是如果車間更加青睞于使用水基冷卻液，液體中應(yīng)該包括EP（極壓）添加劑，增加潤滑和減少發(fā)泡?！叭绻a(chǎn)生很多泡沫，”戴維斯說，“切屑就不會(huì)按著預(yù)定的方式排出?！彼€補(bǔ)充到，另一種提高潤滑并且提高刀具壽命方法是刀具涂層，例如氮鋁化鈦（TiAlN）。TiAlN具有很高的硬度，當(dāng)鉆削像不銹鋼這樣的難加工金屬材料時(shí)，帶有TiAlN涂層的刀具能有效地減少熱量沖擊。威斯康星州簡斯維爾微型刀具公司的總經(jīng)理大衛(wèi)伯頓，對(duì)微加工刀具的小批量涂層有不同的看法，他說：“對(duì)直徑小于0.020英寸的刀具涂層，會(huì)對(duì)從刀具的加工質(zhì)量到刀具的壽命等每一加工方面都產(chǎn)生消極影響”。因?yàn)樾〉毒叩耐繉硬荒軌蜃龅米銐虮?，這樣涂層就會(huì)改變刀具的前角和后角，從而不利于加工。不過，更薄涂層的開發(fā)正在繼續(xù)，伯頓表示，現(xiàn)在微型刀具公司除了生產(chǎn)銷售微型銑刀、刨刀和微型鉆頭外，還在和其他公司合作致力于開發(fā)一種亞細(xì)微涂層。伯頓說：“我們計(jì)劃這種圖層刀具會(huì)在六個(gè)月到一年的時(shí)間內(nèi)上市?！蔽⑿豌@公司的產(chǎn)品主要是用于電路板加工的鉆頭，但也可用于有效的切削金屬。所有的刀具都沒帶有內(nèi)冷能力?！拔矣幸粋€(gè)客戶想要在不銹鋼上面鉆一個(gè)0.004英寸的孔，他當(dāng)時(shí)非常驚訝這能用一把加工電路板的鉆頭完成?！辈D還補(bǔ)充說，“采用啄式進(jìn)給并選擇高的主軸速度可以提高鉆頭的效率?！蔽⒓庸さ毒咭褂枚喔叩霓D(zhuǎn)速，這主要依賴于車間所使用的數(shù)控機(jī)床和刀具的直徑，所需的轉(zhuǎn)速隨刀具直徑的增加而加快（注：切削速度公式為sfm=刀具直徑×0.26×主軸轉(zhuǎn)速）。雖然相對(duì)較低，但伯頓的客戶也成功地應(yīng)用過每分鐘5000轉(zhuǎn)的加工速度。伯頓說：“我們建議我們的用戶找到一個(gè)震動(dòng)最小的最高轉(zhuǎn)速——最佳加工速度?！睘榱藴p少震動(dòng)，在用小的切削力通過刀具的前傾面去除適當(dāng)?shù)慕饘贂r(shí)，應(yīng)使?jié)B入到工件中的切削載荷連續(xù)而充足，如果鉆頭承受的切削載荷太輕，刀具前傾面的磨損速度就會(huì)加快，刀具變鈍，從而影響刀具的使用壽命。這在加工細(xì)孔時(shí)應(yīng)更加注意?！坝脩魝兂３Ｊ褂幂^輕的切削載荷來延長刀具的使用壽命，”伯頓說，“這恰恰會(huì)加快切削刃的磨損，并在刀刃寬出切屑的位置形成圓弧，刀具會(huì)變得像磨削工具一樣把材料強(qiáng)行除掉，只能成為報(bào)廢刀?！辈D認(rèn)為，直徑大于0.001英寸的刀具切削抗力小于0.0001″時(shí)，切削力抗力就已經(jīng)太小了，即使刀具不會(huì)斷裂，過早的摩擦也會(huì)導(dǎo)致刀具壽命縮短。太多的跳動(dòng)也可能是破壞性的，但是影響有多少還值得商榷。伯頓指出，公司打算設(shè)計(jì)一臺(tái)具有0.0003英寸偏差的機(jī)器，用以建立室內(nèi)最壞情況下的銑削場景，還將能夠加工0.004英寸寬的槽，“這遲早會(huì)實(shí)現(xiàn)的”。他還補(bǔ)充：“你還可以試想一下0.0003英寸的跳動(dòng)和只有正常水平三分之一的切削載荷，也就是說0.0001″到0.00015，刀具將會(huì)立即破壞，因?yàn)榈毒叩囊粋€(gè)排屑槽會(huì)承受所有的載荷，然后排屑槽的后面就會(huì)破壞?！彼€指出，在鉆孔時(shí)，小于0.0003英寸的偏差是可接受的，因?yàn)楫?dāng)鉆頭深入孔內(nèi)時(shí)，鉆頭末端的切削刃在外圓柱非加工表面的引導(dǎo)下會(huì)繼續(xù)切削。偏差的最小值隨著深度和直徑比值的增加而迅速減少，這是因?yàn)楫?dāng)鉆頭越深入工件，排屑槽的吸震能力越差。最后強(qiáng)烈的跳動(dòng)導(dǎo)致刀柄繞著刀具的軸線轉(zhuǎn)動(dòng)，而刀尖還仍然保持穩(wěn)定，從而產(chǎn)生使刀具最終斷裂的集中應(yīng)力。插銑雖然通常沒有直徑小于0.002英寸的標(biāo)準(zhǔn)微型鉆頭，但可以用微型端銑刀來“沖”孔?！懊慨?dāng)人們想加工一個(gè)小于0.002英寸的孔時(shí)，他們可以選用端銑刀，效果也不錯(cuò)?！辈D說到。但是這樣加工的孔不能太深，因?yàn)榈毒唧w不長，沒有大的深度直徑比率。因此一把直徑為0.001英寸的端銑刀只能加工最深0.020英寸的孔，而同樣直徑的鉆頭可以加工得更深，因?yàn)殂@頭的設(shè)計(jì)使載荷全部作用在刀尖上，進(jìn)而傳到刀柄上被吸收。市面上能提供最小5微米（0.0002英寸）的端銑刀，但是并沒有大量銷售?！爱?dāng)人們想買這樣的刀具時(shí)，我非常嚴(yán)肅的試著說服他們不要買，因?yàn)槲覀儾幌矚g制作這樣的刀具?！辈D說到。這種刀具的主要問題是，不但這種刀具的硬質(zhì)合金齒處于亞細(xì)微尺寸，而且當(dāng)一把刀有多個(gè)齒時(shí)，每個(gè)齒的尺寸還要保持一致。伯頓道：“一把直徑5微米的端銑刀在其基體上就夾持大約10個(gè)刀齒?！彼€補(bǔ)充說，他曾經(jīng)看到過帶有0.2微米齒的粉末冶金硬質(zhì)合金刀具，這是商業(yè)上能提供齒的尺寸的一半，但它還包括0.5和0.6微米的小齒?！叭绻X的尺寸不統(tǒng)一，小齒是發(fā)揮不出作用的”。墜電火花加工應(yīng)用墜電火花的電火花加工是另一種微孔加工方式。這不同于將放電導(dǎo)線穿過工件的電火花加工方式，應(yīng)用墜電火花加工的微孔更加精密和精確，但同時(shí)花費(fèi)也會(huì)很高。墜電火花加工深細(xì)孔時(shí)，要用一個(gè)導(dǎo)電管作為電極。加工小而淺的孔時(shí)，需要用到一根導(dǎo)線或棒，“我們盡量用導(dǎo)管做電極，”位于密歇根州的牧野公司總經(jīng)理JeffKiszonas說道，導(dǎo)管的排渣孔能使加工的孔有大的深度直徑比，并能夠在加工中將孔底的熔渣排除孔外。他又補(bǔ)充道“但是另一方面，沒人能制出小于一定直徑的導(dǎo)管?！币恍┕?yīng)商能提供直徑小于0.003英寸的導(dǎo)管可以加工出0.0038英寸的孔?！，F(xiàn)在Makino公司生產(chǎn)的雙邊墜電火花加工設(shè)備能夠加工出0.00044英寸（11微米）的微孔，這種設(shè)備主要用于孔的精加工。最近，在日本這種機(jī)床的開發(fā)人員用兩分鐘加工了八個(gè)這樣的孔，并用四十秒穿透了0.0010英寸厚的碳化鎢板。加工電極為一個(gè)銀鎢合金棒，由于電火花加工中在電極和工件間存在放電間隙，所以，所加工孔的直徑會(huì)比電極直徑大0.00020英寸。當(dāng)加工上述尺寸的孔時(shí)，旋轉(zhuǎn)的導(dǎo)棒上包裹著通電的放電導(dǎo)線。精加工時(shí)需要一個(gè)W軸附件，用來夾持電極導(dǎo)向的模具，另外還需要一個(gè)中間導(dǎo)向件，當(dāng)電極旋轉(zhuǎn)時(shí)用來來防止其彎曲和擺動(dòng)。應(yīng)用這種加工方式的機(jī)床適合于加工直徑小于0.005英寸的孔。另一種墜電電火花加工微型孔機(jī)床是三菱VA10機(jī)床，