




已閱讀5頁,還剩4頁未讀, 繼續(xù)免費(fèi)閱讀
版權(quán)說明:本文檔由用戶提供并上傳,收益歸屬內(nèi)容提供方,若內(nèi)容存在侵權(quán),請(qǐng)進(jìn)行舉報(bào)或認(rèn)領(lǐng)
文檔簡介
中國機(jī)械工程學(xué)刊第二十七卷第期第707715頁(民國九十五)JournaloftheChineseSocietyofMechanicalEngineers,Vol.27,No.6,pp.707715(2006)-707-TheStudyofNanometer-GradeGrindingSurfaceforPrecisionMoldsHo-HuaChung*,K.L.Yang*andHsin-TzuLiao*Keywords:Precisiongrinding,Surfaceroughness,Grindingspeed.ABSTRACTTheSKHmoldsteelswerepre-processed,groundbytheprecisesharpeningstonetohaveRa=10-15mforsubsequentprecisegrindingallowance,andthenpreciselygroundbytheCBNgrindingwheel.Theinfluenceofthemainaxelrotationspeedandthesamplehardnessonthegrindingsituationwasdiscussedinthisstudy.TheresultshowsthatthesurfaceroughnessofthelowhardnessSKH51moldsteelcouldbeimprovedmarkedlyasrotationspeedincreased.Onthecontrary,thereisnoobviousimprovementforthehighhardnessSKH59moldsteel.Withincreasingrotationspeed,thesurfaceroughnessofworkpiecesimprovedsignificantlyduetotheincreasingofgrindingforce.However,athighrotationspeed,itwasunabletogetfurtherimprovementsincethegrindingforcenearlyremainingthesamelevel,causingthelessimprovementonthesurfaceroughnessofworkpieces.INTRODUCTIONCuttingmachiningtechnologyisamongthemosteffectivemethodsformoldmachining.Atpresent,machiningbyusingCNClatheswithmillingturretandendmillingmachininginaleadingCNCmachinecenterarethemostcommonmethodsforproductsmachining.However,aftertheroughmachining,thesurfaceofthemoldisextremelyrough.Tosmooththemoldsurface,itshouldbetreatedagainbythefinishmachiningandhandpolishing.Thisprocessreliesonexperiencedtechnician,anditcostsalongtime.Moreover,theprecisionandthequalityofmoldsaredifficulttobefurtherenhancedbythemanualoperation.Therefore,themaingoalofhigh-speedmoldprocessingistoobtainthehighprecisionoffreecurvesurface,toshortenthepolishingoperationtime,andtolowerthemanufacturingcost.Especially,intherecentyears,thecombinationofhigh-speedmoldprocessingwithhighhardnessmaterialsisusuallyusedinthemoldindustrytoenhancethecompetitivenessofprocessingtechnology.Inordertoobtainsubmicron-grade(10-7-10-8m)shapeaccuracyandnanometer-grade(10-9m)surfaceroughness,diamondmilling,diamondlathing,anddiamondgrindingareusuallyusedinultraprecisionmachining.ComputersimulationdonebyHasegawaandMiyazimapointedoutthattheimprovementofsurfaceroughnessofworkpieceswouldreachasaturationvalueunderalongtimepolish,anditshardtobefurtherimproved.Weckdevelopedanultraprecisionmachiningbyusingadiamond-cuttingtool,bywhichthesurfaceroughnessofworkpiecescouldbereducedtobelow5nm.Asaconsequence,themanufacturedminiaturecomponentscouldalsobeappliedinthesemiconductorindustry.Takeuchidevelopedafive-axleultraprecisionmachine,whichhavehydropressureballscrewsandaservomotorwithinitscap.Thismachineusuallyattachedasuper-resolutionopticalencoderwith6,400millionpulsesperrevolution.Thesurfaceroughnesscouldbereducedtoabout50nmunderextremelowfeedingrate,becausetherewerenofrictionforceandbacklashquestions.Itisnecessaryformachiningtoolstohaveexcellentdynamiccharacteristicsandhighrigidityespeciallyformachinigbrittlematerials.PatentTetraform“C”developedbyStephensonandCorbettreportedthatthesurfacefinishwasproducedbetterthan10nmbyusinga76mCBNwheelandtheelectrolyticin-processdressing(ELID)assistedgrinding.Combinationofthehigh-rigidityPaperReceivedAugust,2006.RevisedNovember,2006.AcceptedNovember,2006.AuthorforCorrespondence:Ho-HuaChung*CorrespondingAuthor:AssociateProfessor,DepartmentofMechanicalandAutomationEngineering,KaoYuanUniversity,KaohsiungCounty,Taiwan82101,R.O.C.,Email:.tw*AssistantProfessor,DepartmentofElectronicsEngineering,KaoYuanUniversity,KaohsiungCounty,Taiwan82101,R.O.C.,Email:.tw*AssociateProfessor,DepartmentofBiochemicalEngineering,KaoYuanUniversity,KaohsiungCounty,Taiwan82101,R.O.C.,Email:.twJ.CSMEVol.27,NO.6(2006)-708-machineandmanufacturingprocess,theremovingrateofultraprecisionmachiningcouldbeincreasedsignificantly.Shapeaccuracyandsurfaceroughnessarealsoveryimportantinthesemiconductorindustry.Surfaceroughnessdemandingforsiliconwaferisaboutatnanometergrade.Surfaceroughnessforoptoelectronicsandmemorydevicesisanimportantfactordirectlyaffectingtheperformanceofproduct.Inbrief,thecurrenttrendsinultraprecisemachiningaretoachievenanometer-grademillingandturninginhardenedsteels,toimprovetheprecisionofproducts,toextendthelifeofprecisionmolds,andtoreductionofsurfaceroughnessofworkpieces.Inordertosaveenergyandenvironmentalconservation,surfaceroughnessindegreeofnanometeroffastenersfortransmissionpartsusedinvehicleshasincreaseditsessentiality.Atpresent,hardenedmoldsteel,whichisacommonprecisionfastenermaterial,isusuallymanufacturedbyprecisegrinding.Inthefuture,high-efficiencyprecisegrindingandvariantnanometerhardturningtechnologieswillbedevelopedforgrindingprecisionmolds.Inthisresearch,SKHtoolsteelsarechosenasthemoldworkpieces,andtheeffectofgrindingspeed,materialhardness,grindingforceandfeedingrateonthesurfaceroughnessofworkpiecewillbestudied.EXPERIMENTMETHODEquipmentalset-upInthisstudy,ahighrotationspeedmicro-grinderinstallingtheperipheralmeasurementsystemandmanykindsofdifferentprocessingequipment(suchasnumericalcontrollathe/millingmachine,fourthaxle)wereusedtoconducttheresearch.AsillustratedinFig.1,theoperationproceduresofthishighrotationspeedautomaticprecisemicro-grinderwereshowed.Firstly,afterheattreatment,thehighhardnessmaterialwaspretreatedbydiamondmachininganddiamondcutting.Secondly,thesurfaceroughnessofworkpieceswasreducedtoRa=1015mforsubsequentprecisegrindingallowance.Thirdly,matchingCBNgrindingwheelatFigure1:Schematicillustrationofhighrotationspeedmicro-grinder.H.H.Chungetal.:TheStudyofNanometer-GradeGrindingSurface.-709-highrotationspeed,XYZaxleandthefourthaxlereciprocationwithmoves,thecurvedsurfaceandlinegrinding-truncatingbythediamondscribingtool,andconstructingtheoutlineofgrinding-truncatingbytheCAD/CAMwithparametersobtainedfromexperiments,theunwantedpartofthesurfaceofworkpiecewasremovedandtheincisiveextremelyhardultramicrondiamondburrorabrasiveparticleswererevealed.Finally,themovementpathofgrindingwheelproducedbythediamondscribingtoolwasduplicatedtotheheat-treatedmoldtoolsteeltohavethemicrometer-gradeprecisecontacttypegrindingandthenthesurfaceroughnesscanreachbelow50nm.ExperimentalprocedureThreetypesofmoldtoolsteels(SKH51,SKH55andSKH59)werechosenastheworksamples,andthenweremarkedwithdifferentcolorsinclassified.Theprocessingofworksampleswascarriedonasthefollowingsteps:(1)Cutting:Roughcuttingtoclosetothesamplelength.(2)Roughmachining:Contourmachiningbythediscorcylindergrindingwheel.Trimming:Trimtwosidesofthecuttingend.(3)CNCroughlathe:Lathetheouterdiameterfromthelatheprogram.(4)CNCroughmilling:Shapemillingfromthemillingprogram.(5)Thermaltreatment:Worksampleswereaustenizedat1165oC,1200oCand1165oC,respectively,andthenquenched.Subsequently,thesampleswereannealedat560oCthreetimestoobtaintheRockwellhardnessof60,63and67HRc.ThechemicalcompositionsofthesamplesweresummarizedinTable1.(6)Precisionlathing:Lathetostandardlength.(7)Precisiongrinding:GrindedtothegeometryasillustratedinFigure2,andthencleanedbeforeconductingtheexperiment.Theworkpeiceswereusingacetoneplacedinanultrasoniccleanercleanedforseveralminutes,andthenthesurfaceroughnessweremeasuredbythesurfaceroughnessmeasurementinstrument.Theworkpeiceswerefixedonthespeedmicro-grinderwithsuper-highrotationspeed(Fig.1).Inordertoinvestigatetheinfluenceofthecuttingspeedandthesamplehardnessonthegrindingsituation,theoperationvariableswererotationspeed,depthofcut,horizontalfeedingrate,coolingjet,concentrationandtemperatureofgrindingslurry.ThedetailedexperimentalconditionwasaslistedinTable2.Table1:ElementsanalysisofthemoldtoolsteelsafterthermaltreatmentChemicalComposition(wt%)TestsampleCCrMoWVCoSKH511.073.562.032.591.76-SKH551.113.922.162.831.745.51SKH591.173.573.990.591.149.34Figure2:Thegeometryoftheprecisiongrindedhexagonpunch.Table2:TheexperimentalconditionsforthegrindingprocessofmoldtoolsItemConditionsTestsamplematerialSKH51,SKH55,SKH59GrindingwheelCBN80N75B11V26,d=125mmRotationspeed(rpm)5000,6500,7000,8000,9000Worktablevelocity(mm/min)90-150Optimumdepthofcut(mm)0.03-0.2Grindingslurrytemperature(oC)Input:28-29;Output:30-31Grindingslurryconcentrationoriginalgrindingfluid/water=3:97CoolingjetVolumetricflowrate:20m3/h,pressure:8barJ.CSMEVol.27,NO.6(2006)-710-Undereachkindofrotationspeed,depthofcut,feedingrate,grindingforce,thevibrationfrequency,andthegrindingtemperatureofgrindingslurryweredeterminedbythehigh-precisionloadcell,thedigitalstoragevibrationsmeasuringmeterandthenon-contactthermometer.Aftergrinding,thesurfacemorphologyofworkpieceswasexaminedbythescanningelectronmicroscope(SEM).Moreover,anenergydispersionspectroscope,theRockwellhardnesstester,andthesurfaceroughnessmeasurementinstrumentwerealsousedtocharacterizethegrindingmechanismofSKHsteelprocessingsurface.Finally,theprocessingefficiencyofhardvehiclemillandprecisiongrindingwasassessedviatheexperimentalresult.RESULTSANDDISCUSSIONSSurfaceBehaviorofCBNGrindingWheelThemajorpurposeofhighspeedmoldprocessingistoobtainthehighaccuracyfreecurvedsurface,toreducethepolishingtime,andtolowerthecost.ThehighefficientgrindingisbytheCBNgrindingwheel,thehighmainaxlerotationspeed,andthehighrateofmovementanddeeperentering.Itscuttingquantitywasseveralhundredtimesthanthetraditionalgrinderandthegrindingwheelshapeisallthesamefromthebeginningtoendduringtheperiodofthewholegrindingprocess.Therefore,thenanometer-gradegrindingsurfacecouldbeobtainedbyomittingtherepairingandmaintainingprocedureofgrindingwheelandthechangeofcuttingcondition.ThehardnessofthemoldsurfacewasusuallyhigherthanHRc60andthegeneralcuttingtoolcouldnotprocessitwhenitssurfacewashardenedafterheattreatment.Moreover,therequestofmoldprecisionandsurfacesmoothnesswastoohightobeestablishedbythegeneralcuttingtool.TheCBNgrindingwheelwasthebestmethodusedfortheprecisionprocessingofmoldsurfacebecauseithadthemulti-cuttingsangleandtheregenerationproperty.Figure3showstherelationshipbetweengrindingforceandcuttingspeedfordifferentSKHmoldsteelmaterialswhenthefeedingrateandthedepthofcutweremaintainedat150mm/minand0.05mm,respectively.ForthethreekindsofSKHmoldsteelmaterials,itisclearthatthegrindingforcedecreasedFigure3:Thevariationofgrindingforceasafunctionofcuttingspeedundertheconditionofthefeedingrateof150m/minandthefeedamountof0.05mm.markedlywhenthecuttingspeedwasincreasedfrom2000to2750m/minandthenapproachedasaturationvalue.ThisresultisduetothefactthattheheatgeneratedfromthegrindingofmoldtoolcanbeeasilydissipatedformCBNgrindingwheelitselfandnottrans
溫馨提示
- 1. 本站所有資源如無特殊說明,都需要本地電腦安裝OFFICE2007和PDF閱讀器。圖紙軟件為CAD,CAXA,PROE,UG,SolidWorks等.壓縮文件請(qǐng)下載最新的WinRAR軟件解壓。
- 2. 本站的文檔不包含任何第三方提供的附件圖紙等,如果需要附件,請(qǐng)聯(lián)系上傳者。文件的所有權(quán)益歸上傳用戶所有。
- 3. 本站RAR壓縮包中若帶圖紙,網(wǎng)頁內(nèi)容里面會(huì)有圖紙預(yù)覽,若沒有圖紙預(yù)覽就沒有圖紙。
- 4. 未經(jīng)權(quán)益所有人同意不得將文件中的內(nèi)容挪作商業(yè)或盈利用途。
- 5. 人人文庫網(wǎng)僅提供信息存儲(chǔ)空間,僅對(duì)用戶上傳內(nèi)容的表現(xiàn)方式做保護(hù)處理,對(duì)用戶上傳分享的文檔內(nèi)容本身不做任何修改或編輯,并不能對(duì)任何下載內(nèi)容負(fù)責(zé)。
- 6. 下載文件中如有侵權(quán)或不適當(dāng)內(nèi)容,請(qǐng)與我們聯(lián)系,我們立即糾正。
- 7. 本站不保證下載資源的準(zhǔn)確性、安全性和完整性, 同時(shí)也不承擔(dān)用戶因使用這些下載資源對(duì)自己和他人造成任何形式的傷害或損失。
最新文檔
- 藥庫設(shè)備維護(hù)管理制度
- 藥店獎(jiǎng)罰規(guī)章管理制度
- 藥店設(shè)備投放管理制度
- 營林防火安全管理制度
- 設(shè)備公司營銷管理制度
- 設(shè)備安全細(xì)節(jié)管理制度
- 設(shè)備現(xiàn)場(chǎng)施工管理制度
- 設(shè)施權(quán)屬清冊(cè)管理制度
- 設(shè)計(jì)單位員工管理制度
- 詐騙公司經(jīng)營管理制度
- 項(xiàng)目部內(nèi)審檢查表
- 森林計(jì)測(cè)學(xué)(測(cè)樹學(xué))智慧樹知到答案章節(jié)測(cè)試2023年浙江農(nóng)林大學(xué)
- 對(duì)外漢語教學(xué)法智慧樹知到答案章節(jié)測(cè)試2023年西北師范大學(xué)
- 春雨計(jì)劃患教指南-高血壓治療與合理用藥
- jgj113-2015建筑玻璃技術(shù)規(guī)范
- 陜西延長石油四海煤化工有限公司金屬鎂廠1萬噸-年金屬鎂生產(chǎn)項(xiàng)目環(huán)評(píng)報(bào)告
- 學(xué)校校本課程開辟匯報(bào)材料
- GB/T 42103-2022游樂園安全風(fēng)險(xiǎn)識(shí)別與評(píng)估
- YY 0780-2018電針治療儀
- 棒球運(yùn)動(dòng)主題教育PPT模板
- GA/T 1556-2019道路交通執(zhí)法人體血液采集技術(shù)規(guī)范
評(píng)論
0/150
提交評(píng)論