外文翻译--注塑模表面自动化磨削和抛光的过程 英文版.pdf

DOI10.1007/s00170-004-2328-8ORIGINALARTICLEIntJAdvManufTechnol(2006)28:6166Fang-JungShiou·Chao-ChangA.Chen·Wen-TuLiAutomatedsurfacefinishingofplasticinjectionmoldsteelwithsphericalgrindingandballburnishingprocessesReceived:30March2004/Accepted:5July2004/Publishedonline:30March2005©Springer-VerlagLondonLimited2005AbstractThisstudyinvestigatesthepossibilitiesofautomatedsphericalgrindingandballburnishingsurfacefinishingpro-cessesinafreeformsurfaceplasticinjectionmoldsteelPDS5onaCNCmachiningcenter.Thedesignandmanufactureofagrindingtoolholderhasbeenaccomplishedinthisstudy.TheoptimalsurfacegrindingparametersweredeterminedusingTaguchisorthogonalarraymethodforplasticinjectionmoldingsteelPDS5onamachiningcenter.Theoptimalsurfacegrind-ingparametersfortheplasticinjectionmoldsteelPDS5werethecombinationofanabrasivematerialofPAAl2O3,agrind-ingspeedof18000rpm,agrindingdepthof20µm,andafeedof50mm/min.ThesurfaceroughnessRaofthespecimencanbeimprovedfromabout1.60µmto0.35µmbyusingtheoptimalparametersforsurfacegrinding.SurfaceroughnessRacanbefurtherimprovedfromabout0.343µmto0.06µmbyusingtheballburnishingprocesswiththeoptimalburnishingparameters.Applyingtheoptimalsurfacegrindingandburnishingparame-terssequentiallytoafine-milledfreeformsurfacemoldinsert,thesurfaceroughnessRaoffreeformsurfaceregiononthetestedpartcanbeimprovedfromabout2.15µmto0.07µm.KeywordsAutomatedsurfacefinishing·Ballburnishingprocess·Grindingprocess·Surfaceroughness·Taguchismethod1IntroductionPlasticsareimportantengineeringmaterialsduetotheirspecificcharacteristics,suchascorrosionresistance,resistancetochemi-cals,lowdensity,andeaseofmanufacture,andhaveincreasinglyF.-J.Shiou(a117)·C.-C.A.Chen·W.-T.LiDepartmentofMechanicalEngineering,NationalTaiwanUniversityofScienceandTechnology,No.43,Section4,KeelungRoad,106Taipei,TaiwanR.O.C.E-mail:shioumail.ntust.edu.twTel.:+88-62-2737-6543Fax:+88-62-2737-6460replacedmetalliccomponentsinindustrialapplications.Injec-tionmoldingisoneoftheimportantformingprocessesforplas-ticproducts.Thesurfacefinishqualityoftheplasticinjectionmoldisanessentialrequirementduetoitsdirecteffectsontheappearanceoftheplasticproduct.Finishingprocessessuchasgrinding,polishingandlappingarecommonlyusedtoimprovethesurfacefinish.Themountedgrindingtools(wheels)havebeenwidelyusedinconventionalmoldanddiefinishingindustries.Thegeometricmodelofmountedgrindingtoolsforautomatedsurfacefinish-ingprocesseswasintroducedin1.Afinishingprocessmodelofsphericalgrindingtoolsforautomatedsurfacefinishingsys-temswasdevelopedin2.Grindingspeed,depthofcut,feedrate,andwheelpropertiessuchasabrasivematerialandabrasivegrainsize,arethedominantparametersforthesphericalgrind-ingprocess,asshowninFig.1.Theoptimalsphericalgrindingparametersfortheinjectionmoldsteelhavenotyetbeeninvesti-gatedbasedintheliterature.Inrecentyears,someresearchhasbeencarriedoutinde-terminingtheoptimalparametersoftheballburnishingpro-cess(Fig.2).Forinstance,ithasbeenfoundthatplasticde-formationontheworkpiecesurfacecanbereducedbyusingatungstencarbideballoraroller,thusimprovingthesurfaceroughness,surfacehardness,andfatigueresistance36.Theburnishingprocessisaccomplishedbymachiningcenters3,4andlathes5,6.Themainburnishingparametershavingsignifi-canteffectsonthesurfaceroughnessareballorrollermaterial,burnishingforce,feedrate,burnishingspeed,lubrication,andnumberofburnishingpasses,amongothers3.Theoptimalsur-faceburnishingparametersfortheplasticinjectionmoldsteelPDS5wereacombinationofgreaselubricant,thetungstencar-bideball,aburnishingspeedof200mm/min,aburnishingforceof300N,andafeedof40µm7.Thedepthofpenetrationoftheburnishedsurfaceusingtheoptimalballburnishingparameterswasabout2.5microns.Theimprovementofthesurfacerough-nessthroughburnishingprocessgenerallyrangedbetween40%and90%37.Theaimofthisstudywastodevelopsphericalgrindingandballburnishingsurfacefinishprocessesofafreeformsurface62plasticinjectionmoldonamachiningcenter.Theflowchartofautomatedsurfacefinishusingsphericalgrindingandballbur-nishingprocessesisshowninFig.3.Webeganbydesigningandmanufacturingthesphericalgrindingtoolanditsalignmentde-viceforuseonamachiningcenter.TheoptimalsurfacesphericalgrindingparametersweredeterminedbyutilizingaTaguchisorthogonalarraymethod.FourfactorsandthreecorrespondinglevelswerethenchosenfortheTaguchisL18matrixexperiment.Theoptimalmountedsphericalgrindingparametersforsurfacegrindingwerethenappliedtothesurfacefinishofafreeformsurfacecarrier.Toimprovethesurfaceroughness,thegroundsurfacewasfurtherburnished,usingtheoptimalballburnishingparameters.Fig.1.SchematicdiagramofthesphericalgrindingprocessFig.2.Schematicdiagramoftheball-burnishingprocessFig.3.Flowchartofautomatedsurfacefinishusingsphericalgrindingandballburnishingprocesses2DesignofthesphericalgrindingtoolanditsalignmentdeviceTocarryoutthepossiblesphericalgrindingprocessofafreeformsurface,thecenteroftheballgrindershouldcoincidewiththez-axisofthemachiningcenter.Themountedsphericalgrindingtoolanditsadjustmentdevicewasdesigned,asshowninFig.4.Theelectricgrinderwasmountedinatoolholderwithtwoad-justablepivotscrews.Thecenterofthegrinderballwaswellalignedwiththehelpoftheconicgrooveofthealignmentcom-ponents.Havingalignedthegrinderball,twoadjustablepivotscrewsweretightened；afterwhich,thealignmentcomponentscouldberemoved.Thedeviationbetweenthecentercoordi-natesoftheballgrinderandthatoftheshankwasabout5µm,whichwasmeasuredbyaCNCcoordinatemeasuringmachine.Theforceinducedbythevibrationofthemachinebedisab-sorbedbyahelicalspring.Themanufacturedsphericalgrind-ingtoolandball-burnishingtoolweremounted,asshowninFig.5.Thespindlewaslockedforboththesphericalgrindingprocessandtheballburnishingprocessbyaspindle-lockingmechanism.63Fig.4.Schematicillustrationofthesphericalgrindingtoolanditsadjust-mentdevice3Planningofthematrixexperiment3.1ConfigurationofTaguchisorthogonalarrayTheeffectsofseveralparameterscanbedeterminedefficientlybyconductingmatrixexperimentsusingTaguchisorthogonalarray8.Tomatchtheaforementionedsphericalgrindingpa-rameters,theabrasivematerialofthegrinderball(withthediam-eterof10mm),thefeedrate,thedepthofgrinding,andtherevolutionoftheelectricgrinderwereselectedasthefourexperi-mentalfactors(parameters)anddesignatedasfactorAtoD(seeTable1)inthisresearch.Threelevels(settings)foreachfactorwereconfiguredtocovertherangeofinterest,andwereidenti-Fig.5.aPhotoofthesphericalgrindingtoolbPhotooftheballburnishingtoolTable1.TheexperimentalfactorsandtheirlevelsFactorLevel123A.AbrasivematerialSiCAl2O3,WAAl2O3,PAB.Feed(mm/min)50100200C.Depthofgrinding(µm)205080D.Revolution(rpm)120001800024000fiedbythedigits1,2,and3.Threetypesofabrasivematerials,namelysiliconcarbide(SiC),whitealuminumoxide(Al2O3,WA),andpinkaluminumoxide(Al2O3,PA),wereselectedandstudied.Threenumericalvaluesofeachfactorweredeterminedbasedonthepre-studyresults.TheL18orthogonalarraywasse-lectedtoconductthematrixexperimentforfour3-levelfactorsofthesphericalgrindingprocess.3.2DefinitionofthedataanalysisEngineeringdesignproblemscanbedividedintosmaller-the-bettertypes,nominal-the-besttypes,larger-the-bettertypes,signed-targettypes,amongothers8.Thesignal-to-noise(S/N)ratioisusedastheobjectivefunctionforoptimizingaproductorprocessdesign.Thesurfaceroughnessvalueofthegroundsur-faceviaanadequatecombinationofgrindingparametersshouldbesmallerthanthatoftheoriginalsurface.Consequently,thesphericalgrindingprocessisanexampleofasmaller-the-bettertypeproblem.TheS/Nratio,isdefinedbythefollowingequation8:=10log10(meansquarequalitycharacteristic)=10log10bracketleftBigg1nnsummationdisplayi=1y2ibracketrightBigg.(1)where:yi:observationsofthequalitycharacteristicunderdifferentnoiseconditionsn:numberofexperimentAftertheS/NratiofromtheexperimentaldataofeachL18orthogonalarrayiscalculated,themaineffectofeachfactorwasdeterminedbyusingananalysisofvariance(ANOVA)tech-niqueandanF-ratiotest8.Theoptimizationstrategyofthe64smaller-thebetterproblemistomaximize,asdefinedbyEq.1.Levelsthatmaximizewillbeselectedforthefactorsthathaveasignificanteffecton.Theoptimalconditionsforsphericalgrindingcanthenbedetermined.4ExperimentalworkandresultsThematerialusedinthisstudywasPDS5toolsteel(equiva-lenttoAISIP20)9,whichiscommonlyusedforthemoldsoflargeplasticinjectionproductsinthefieldofautomobilecom-ponentsanddomesticappliances.ThehardnessofthismaterialisaboutHRC33(HS46)9.Onespecificadvantageofthisma-terialisthataftermachining,themoldcanbedirectlyusedforfurtherfinishingprocesseswithoutheattreatmentduetoitsspecialpre-treatment.Thespecimensweredesignedandmanu-facturedsothattheycouldbemountedonadynamometertomeasurethereactionforce.ThePDS5specimenwasroughlyma-chinedandthenmountedonthedynamometertocarryoutthefinemillingonathree-axismachiningcentermadebyYang-IronCompany(typeMV-3A),equippedwithaFUNUCCom-panyNC-controller(type0M)10.Thepre-machinedsurfaceroughnesswasmeasured,usingHommelwerkeT4000equip-ment,tobeabout1.6µm.Figure6showstheexperimentalset-upofthesphericalgrindingprocess.AMP10touch-triggerprobemadebytheRenishawCompanywasalsointegratedwiththemachiningcentertoolmagazinetomeasureanddeterminethecoordinatedoriginofthespecimentobeground.TheNCcodesneededfortheball-burnishingpathweregeneratedbyPowerMILLCAMsoftware.ThesecodescanbetransmittedtotheCNCcontrollerofthemachiningcenterviaRS232serialinterface.Table2summarizesthemeasuredgroundsurfaceroughnessvalueRaandthecalculatedS/NratioofeachL18orthogonalar-rayusingEq.1,afterhavingexecutedthe18matrixexperiments.TheaverageS/Nratioforeachlevelofthefourfactorscanbeobtained,aslistedinTable3,bytakingthenumericalvaluespro-videdinTable2.TheaverageS/NratioforeachlevelofthefourfactorsisshowngraphicallyinFig.7.Fig.6.Experimentalset-uptodeterminetheop-timalsphericalgrindingparametersTable2.GroundsurfaceroughnessofPDS5specimenExp.InnerarrayMeasuredsurfaceResponseno.(controlfactors)roughnessvalue(Ra)ABCDy1y2y3S/NratioMean(µm)(µm)(µm)(dB)y(µm)111110.350.350.359.1190.350212220.370.360.388.6340.370313330.410.440.407.5970.417421230.630.650.643.8760.640522310.730.770.782.3800.760623120.450.420.397.5200.420731320.340.310.329.8010.323832130.270.250.2811.4710.267933210.320.320.329.8970.3201011220.350.390.408.3900.3801112330.410.500.436.9680.4471213110.400.390.427.8830.4031321130.330.340.319.7120.3271422210.480.500.476.3120.4831523320.570.610.534.8680.5701631310.590.550.545.0300.5601732120.360.360.358.9540.3571833230.570.530.535.2930.543Table3.AverageS/Nratiosbyfactorlevels(dB)FactorABCDLevel18.0997.6559.1106.770Level25.7787.4537.0678.028Level38.4087.1766.1077.486Effect2.6300.4793.0031.258Rank2413Mean7.428Thegoalinthesphericalgrindingprocessistominimizethesurfaceroughnessvalueofthegroundspecimenbydetermin-ingtheoptimallevelofeachfactor.Sincelogisamonotonedecreasingfunction,weshouldmaximizetheS/Nratio.Conse-quently,wecandeterminetheoptimallevelforeachfactorasbeingthelevelthathasthehighestvalueof.Therefore,based