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中國機械工程學刊第二十七卷第六期第707715頁民國九十五年JOURNALOFTHECHINESESOCIETYOFMECHANICALENGINEERS,VOL27,NO6,PP7077152006707THESTUDYOFNANOMETERGRADEGRINDINGSURFACEFORPRECISIONMOLDSHOHUACHUNG,KLYANGANDHSINTZULIAOKEYWORDSPRECISIONGRINDING,SURFACEROUGHNESS,GRINDINGSPEEDABSTRACTTHESKHMOLDSTEELSWEREPREPROCESSED,GROUNDBYTHEPRECISESHARPENINGSTONETOHAVERA1015ΜMFORSUBSEQUENTPRECISEGRINDINGALLOWANCE,ANDTHENPRECISELYGROUNDBYTHECBNGRINDINGWHEELTHEINFLUENCEOFTHEMAINAXELROTATIONSPEEDANDTHESAMPLEHARDNESSONTHEGRINDINGSITUATIONWASDISCUSSEDINTHISSTUDYTHERESULTSHOWSTHATTHESURFACEROUGHNESSOFTHELOWHARDNESSSKH51MOLDSTEELCOULDBEIMPROVEDMARKEDLYASROTATIONSPEEDINCREASEDONTHECONTRARY,THEREISNOOBVIOUSIMPROVEMENTFORTHEHIGHHARDNESSSKH59MOLDSTEELWITHINCREASINGROTATIONSPEED,THESURFACEROUGHNESSOFWORKPIECESIMPROVEDSIGNIFICANTLYDUETOTHEINCREASINGOFGRINDINGFORCEHOWEVER,ATHIGHROTATIONSPEED,ITWASUNABLETOGETFURTHERIMPROVEMENTSINCETHEGRINDINGFORCENEARLYREMAININGTHESAMELEVEL,CAUSINGTHELESSIMPROVEMENTONTHESURFACEROUGHNESSOFWORKPIECESINTRODUCTIONCUTTINGMACHININGTECHNOLOGYISAMONGTHEMOSTEFFECTIVEMETHODSFORMOLDMACHININGATPRESENT,MACHININGBYUSINGCNCLATHESWITHMILLINGTURRETANDENDMILLINGMACHININGINALEADINGCNCMACHINECENTERARETHEMOSTCOMMONMETHODSFORPRODUCTSMACHININGHOWEVER,AFTERTHEROUGHMACHINING,THESURFACEOFTHEMOLDISEXTREMELYROUGHTOSMOOTHTHEMOLDSURFACE,ITSHOULDBETREATEDAGAINBYTHEFINISHMACHININGANDHANDPOLISHINGTHISPROCESSRELIESONEXPERIENCEDTECHNICIAN,ANDITCOSTSALONGTIMEMOREOVER,THEPRECISIONANDTHEQUALITYOFMOLDSAREDIFFICULTTOBEFURTHERENHANCEDBYTHEMANUALOPERATIONTHEREFORE,THEMAINGOALOFHIGHSPEEDMOLDPROCESSINGISTOOBTAINTHEHIGHPRECISIONOFFREECURVESURFACE,TOSHORTENTHEPOLISHINGOPERATIONTIME,ANDTOLOWERTHEMANUFACTURINGCOSTESPECIALLY,INTHERECENTYEARS,THECOMBINATIONOFHIGHSPEEDMOLDPROCESSINGWITHHIGHHARDNESSMATERIALSISUSUALLYUSEDINTHEMOLDINDUSTRYTOENHANCETHECOMPETITIVENESSOFPROCESSINGTECHNOLOGYINORDERTOOBTAINSUBMICRONGRADE107108MSHAPEACCURACYANDNANOMETERGRADE109MSURFACEROUGHNESS,DIAMONDMILLING,DIAMONDLATHING,ANDDIAMONDGRINDINGAREUSUALLYUSEDINULTRAPRECISIONMACHININGCOMPUTERSIMULATIONDONEBYHASEGAWAANDMIYAZIMAPOINTEDOUTTHATTHEIMPROVEMENTOFSURFACEROUGHNESSOFWORKPIECESWOULDREACHASATURATIONVALUEUNDERALONGTIMEPOLISH,ANDIT’SHARDTOBEFURTHERIMPROVEDWECKDEVELOPEDANULTRAPRECISIONMACHININGBYUSINGADIAMONDCUTTINGTOOL,BYWHICHTHESURFACEROUGHNESSOFWORKPIECESCOULDBEREDUCEDTOBELOW5NMASACONSEQUENCE,THEMANUFACTUREDMINIATURECOMPONENTSCOULDALSOBEAPPLIEDINTHESEMICONDUCTORINDUSTRYTAKEUCHIDEVELOPEDAFIVEAXLEULTRAPRECISIONMACHINE,WHICHHAVEHYDROPRESSUREBALLSCREWSANDASERVOMOTORWITHINITSCAPTHISMACHINEUSUALLYATTACHEDASUPERRESOLUTIONOPTICALENCODERWITH6,400MILLIONPULSESPERREVOLUTIONTHESURFACEROUGHNESSCOULDBEREDUCEDTOABOUT50NMUNDEREXTREMELOWFEEDINGRATE,BECAUSETHEREWERENOFRICTIONFORCEANDBACKLASHQUESTIONSITISNECESSARYFORMACHININGTOOLSTOHAVEEXCELLENTDYNAMICCHARACTERISTICSANDHIGHRIGIDITYESPECIALLYFORMACHINIGBRITTLEMATERIALSPATENTTETRAFORM“C”DEVELOPEDBYSTEPHENSONANDCORBETTREPORTEDTHATTHESURFACEFINISHWASPRODUCEDBETTERTHAN10NMBYUSINGA76ΜMCBNWHEELANDTHEELECTROLYTICINPROCESSDRESSINGELIDASSISTEDGRINDINGCOMBINATIONOFTHEHIGHRIGIDITYPAPERRECEIVEDAUGUST,2006REVISEDNOVEMBER,2006ACCEPTEDNOVEMBER,2006AUTHORFORCORRESPONDENCEHOHUACHUNGCORRESPONDINGAUTHORASSOCIATEPROFESSOR,DEPARTMENTOFMECHANICALANDAUTOMATIONENGINEERING,KAOYUANUNIVERSITY,KAOHSIUNGCOUNTY,TAIWAN82101,ROC,EMAILHOHUACCKYUEDUTWASSISTANTPROFESSOR,DEPARTMENTOFELECTRONICSENGINEERING,KAOYUANUNIVERSITY,KAOHSIUNGCOUNTY,TAIWAN82101,ROC,EMAILKLYANGCCKYUEDUTWASSOCIATEPROFESSOR,DEPARTMENTOFBIOCHEMICALENGINEERING,KAOYUANUNIVERSITY,KAOHSIUNGCOUNTY,TAIWAN82101,ROC,EMAILHTLIAWCCKYUEDUTWJCSMEVOL27,NO62006708MACHINEANDMANUFACTURINGPROCESS,THEREMOVINGRATEOFULTRAPRECISIONMACHININGCOULDBEINCREASEDSIGNIFICANTLYSHAPEACCURACYANDSURFACEROUGHNESSAREALSOVERYIMPORTANTINTHESEMICONDUCTORINDUSTRYSURFACEROUGHNESSDEMANDINGFORSILICONWAFERISABOUTATNANOMETERGRADESURFACEROUGHNESSFOROPTOELECTRONICSANDMEMORYDEVICESISANIMPORTANTFACTORDIRECTLYAFFECTINGTHEPERFORMANCEOFPRODUCTINBRIEF,THECURRENTTRENDSINULTRAPRECISEMACHININGARETOACHIEVENANOMETERGRADEMILLINGANDTURNINGINHARDENEDSTEELS,TOIMPROVETHEPRECISIONOFPRODUCTS,TOEXTENDTHELIFEOFPRECISIONMOLDS,ANDTOREDUCTIONOFSURFACEROUGHNESSOFWORKPIECESINORDERTOSAVEENERGYANDENVIRONMENTALCONSERVATION,SURFACEROUGHNESSINDEGREEOFNANOMETEROFFASTENERSFORTRANSMISSIONPARTSUSEDINVEHICLESHASINCREASEDITSESSENTIALITYATPRESENT,HARDENEDMOLDSTEEL,WHICHISACOMMONPRECISIONFASTENERMATERIAL,ISUSUALLYMANUFACTUREDBYPRECISEGRINDINGINTHEFUTURE,HIGHEFFICIENCYPRECISEGRINDINGANDVARIANTNANOMETERHARDTURNINGTECHNOLOGIESWILLBEDEVELOPEDFORGRINDINGPRECISIONMOLDSINTHISRESEARCH,SKHTOOLSTEELSARECHOSENASTHEMOLDWORKPIECES,ANDTHEEFFECTOFGRINDINGSPEED,MATERIALHARDNESS,GRINDINGFORCEANDFEEDINGRATEONTHESURFACEROUGHNESSOFWORKPIECEWILLBESTUDIEDEXPERIMENTMETHODEQUIPMENTALSETUPINTHISSTUDY,AHIGHROTATIONSPEEDMICROGRINDERINSTALLINGTHEPERIPHERALMEASUREMENTSYSTEMANDMANYKINDSOFDIFFERENTPROCESSINGEQUIPMENTSUCHASNUMERICALCONTROLLATHE/MILLINGMACHINE,FOURTHAXLEWEREUSEDTOCONDUCTTHERESEARCHASILLUSTRATEDINFIG1,THEOPERATIONPROCEDURESOFTHISHIGHROTATIONSPEEDAUTOMATICPRECISEMICROGRINDERWERESHOWEDFIRSTLY,AFTERHEATTREATMENT,THEHIGHHARDNESSMATERIALWASPRETREATEDBYDIAMONDMACHININGANDDIAMONDCUTTINGSECONDLY,THESURFACEROUGHNESSOFWORKPIECESWASREDUCEDTORA1015ΜMFORSUBSEQUENTPRECISEGRINDINGALLOWANCETHIRDLY,MATCHINGCBNGRINDINGWHEELATFIGURE1SCHEMATICILLUSTRATIONOFHIGHROTATIONSPEEDMICROGRINDERHHCHUNGETALTHESTUDYOFNANOMETERGRADEGRINDINGSURFACE709HIGHROTATIONSPEED,XYZAXLEANDTHEFOURTHAXLERECIPROCATIONWITHMOVES,THECURVEDSURFACEANDLINEGRINDINGTRUNCATINGBYTHEDIAMONDSCRIBINGTOOL,ANDCONSTRUCTINGTHEOUTLINEOFGRINDINGTRUNCATINGBYTHECAD/CAMWITHPARAMETERSOBTAINEDFROMEXPERIMENTS,THEUNWANTEDPARTOFTHESURFACEOFWORKPIECEWASREMOVEDANDTHEINCISIVEEXTREMELYHARDULTRAMICRONDIAMONDBURRORABRASIVEPARTICLESWEREREVEALEDFINALLY,THEMOVEMENTPATHOFGRINDINGWHEELPRODUCEDBYTHEDIAMONDSCRIBINGTOOLWASDUPLICATEDTOTHEHEATTREATEDMOLDTOOLSTEELTOHAVETHEMICROMETERGRADEPRECISECONTACTTYPEGRINDINGANDTHENTHESURFACEROUGHNESSCANREACHBELOW50NMEXPERIMENTALPROCEDURETHREETYPESOFMOLDTOOLSTEELSSKH51,SKH55ANDSKH59WERECHOSENASTHEWORKSAMPLES,ANDTHENWEREMARKEDWITHDIFFERENTCOLORSINCLASSIFIEDTHEPROCESSINGOFWORKSAMPLESWASCARRIEDONASTHEFOLLOWINGSTEPS1CUTTINGROUGHCUTTINGTOCLOSETOTHESAMPLELENGTH2ROUGHMACHININGCONTOURMACHININGBYTHEDISCORCYLINDERGRINDINGWHEELTRIMMINGTRIMTWOSIDESOFTHECUTTINGEND3CNCROUGHLATHELATHETHEOUTERDIAMETERFROMTHELATHEPROGRAM4CNCROUGHMILLINGSHAPEMILLINGFROMTHEMILLINGPROGRAM5THERMALTREATMENTWORKSAMPLESWEREAUSTENIZEDAT1165OC,1200OCAND1165OC,RESPECTIVELY,ANDTHENQUENCHEDSUBSEQUENTLY,THESAMPLESWEREANNEALEDAT560OCTHREETIMESTOOBTAINTHEROCKWELLHARDNESSOF60,63AND67HRCTHECHEMICALCOMPOSITIONSOFTHESAMPLESWERESUMMARIZEDINTABLE16PRECISIONLATHINGLATHETOSTANDARDLENGTH7PRECISIONGRINDINGGRINDEDTOTHEGEOMETRYASILLUSTRATEDINFIGURE2,ANDTHENCLEANEDBEFORECONDUCTINGTHEEXPERIMENTTHEWORKPEICESWEREUSINGACETONEPLACEDINANULTRASONICCLEANERCLEANEDFORSEVERALMINUTES,ANDTHENTHESURFACEROUGHNESSWEREMEASUREDBYTHESURFACEROUGHNESSMEASUREMENTINSTRUMENTTHEWORKPEICESWEREFIXEDONTHESPEEDMICROGRINDERWITHSUPERHIGHROTATIONSPEEDFIG1INORDERTOINVESTIGATETHEINFLUENCEOFTHECUTTINGSPEEDANDTHESAMPLEHARDNESSONTHEGRINDINGSITUATION,THEOPERATIONVARIABLESWEREROTATIONSPEED,DEPTHOFCUT,HORIZONTALFEEDINGRATE,COOLINGJET,CONCENTRATIONANDTEMPERATUREOFGRINDINGSLURRYTHEDETAILEDEXPERIMENTALCONDITIONWASASLISTEDINTABLE2TABLE1ELEMENTSANALYSISOFTHEMOLDTOOLSTEELSAFTERTHERMALTREATMENTCHEMICALCOMPOSITIONWTTESTSAMPLECCRMOWVCOSKH51107356203259176SKH55111392216283174551SKH59117357399059114934FIGURE2THEGEOMETRYOFTHEPRECISIONGRINDEDHEXAGONPUNCHTABLE2THEEXPERIMENTALCONDITIONSFORTHEGRINDINGPROCESSOFMOLDTOOLSITEMCONDITIONSTESTSAMPLEMATERIALSKH51,SKH55,SKH59GRINDINGWHEELCBN80N75B11V26,D125MMROTATIONSPEEDRPM5000,6500,7000,8000,9000WORKTABLEVELOCITYMM/MIN90150OPTIMUMDEPTHOFCUTMM00302GRINDINGSLURRYTEMPERATUREOCINPUT2829；OUTPUT3031GRINDINGSLURRYCONCENTRATIONORIGINALGRINDINGFLUID/WATER397COOLINGJETVOLUMETRICFLOWRATE20M3/H，PRESSURE8BARJCSMEVOL27,NO62006710UNDEREACHKINDOFROTATIONSPEED,DEPTHOFCUT,FEEDINGRATE,GRINDINGFORCE,THEVIBRATIONFREQUENCY,ANDTHEGRINDINGTEMPERATUREOFGRINDINGSLURRYWEREDETERMINEDBYTHEHIGHPRECISIONLOADCELL,THEDIGITALSTORAGEVIBRATIONSMEASURINGMETERANDTHENONCONTACTTHERMOMETERAFTERGRINDING,THESURFACEMORPHOLOGYOFWORKPIECESWASEXAMINEDBYTHESCANNINGELECTRONMICROSCOPESEMMOREOVER,ANENERGYDISPERSIONSPECTROSCOPE,THEROCKWELLHARDNESSTESTER,ANDTHESURFACEROUGHNESSMEASUREMENTINSTRUMENTWEREALSOUSEDTOCHARACTERIZETHEGRINDINGMECHANISMOFSKHSTEELPROCESSINGSURFACEFINALLY,THEPROCESSINGEFFICIENCYOFHARDVEHICLEMILLANDPRECISIONGRINDINGWASASSESSEDVIATHEEXPERIMENTALRESULTRESULTSANDDISCUSSIONSSURFACEBEHAVIOROFCBNGRINDINGWHEELTHEMAJORPURPOSEOFHIGHSPEEDMOLDPROCESSINGISTOOBTAINTHEHIGHACCURACYFREECURVEDSURFACE,TOREDUCETHEPOLISHINGTIME,ANDTOLOWERTHECOSTTHEHIGHEFFICIENTGRINDINGISBYTHECBNGRINDINGWHEEL,THEHIGHMAINAXLEROTATIONSPEED,ANDTHEHIGHRATEOFMOVEMENTANDDEEPERENTERINGITSCUTTINGQUANTITYWASSEVERALHUNDREDTIMESTHANTHETRADITIONALGRINDERANDTHEGRINDINGWHEELSHAPEISALLTHESAMEFROMTHEBEGINNINGTOENDDURINGTHEPERIODOFTHEWHOLEGRINDINGPROCESSTHEREFORE,THENANOMETERGRADEGRINDINGSURFACECOULDBEOBTAINEDBYOMITTINGTHEREPAIRINGANDMAINTAININGPROCEDUREOFGRINDINGWHEELANDTHECHANGEOFCUTTINGCONDITIONTHEHARDNESSOFTHEMOLDSURFACEWASUSUALLYHIGHERTHANHRC60ANDTHEGENERALCUTTINGTOOLCOULDNOTPROCESSITWHENITSSURFACEWASHARDENEDAFTERHEATTREATMENTMOREOVER,THEREQUESTOFMOLDPRECISIONANDSURFACESMOOTHNESSWASTOOHIGHTOBEESTABLISHEDBYTHEGENERALCUTTINGTOOLTHECBNGRINDINGWHEELWASTHEBESTMETHODUSEDFORTHEPRECISIONPROCESSINGOFMOLDSURFACEBECAUSEITHADTHEMULTICUTTINGSANGLEANDTHEREGENERATIONPROPERTYFIGURE3SHOWSTHERELATIONSHIPBETWEENGRINDINGFORCEANDCUTTINGSPEEDFORDIFFERENTSKHMOLDSTEELMATERIALSWHENTHEFEEDINGRATEANDTHEDEPTHOFCUTWEREMAINTAINEDAT150MM/MINAND005MM,RESPECTIVELYFORTHETHREEKINDSOFSKHMOLDSTEELMATERIALS,ITISCLEARTHATTHEGRINDINGFORCEDECREASEDFIGURE3THEVARIATIONOFGRINDINGFORCEASAFUNCTIONOFCUTTINGSPEEDUNDERTHECONDITIONOFTHEFEEDINGRATEOF150M/MINANDTHEFEEDAMOUNTOF005MMMARKEDLYWHENTHECUTTINGSPEEDWASINCREASEDFROM2000TO2750M/MINANDTHENAPPROACHEDASATURATIONVALUETHISRESULTISDUETOTHEFACTTHATTHEH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