文献翻译原文通过实验设计优化微注射成型工艺Word文档格式.docx

文献翻译原文通过实验设计优化微注射成型工艺Word文档格式.docx

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机械设计制造及其自动化

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2014年5月26日

1.Introduction

MicroInjectionMoulding（MIM）isarelativelynewtechnologywhichispopularintheindustryformicromanufacturebecauseofitsmassproductioncapabilityandlowcomponentcost.InordertoachievethehighestqualitycomponentswithminimalcostsusingMIMitisimportanttounderstandtheprocessandidentifytheeffectsofdifferentindependentparameters.OneofthemethodsthatcanbeemployedtoinvestigatetheoveralloperationofMIMisDesignofExperiments（DoE）.Ingeneral,DoEcanbeusedtocollectdatafromanyprocessandgainanunderstandingoftheprocessthroughdataanalysis.Thisprocedurecanhelptooptimisetheprocessandeventuallyleadtoqualityimprovements.

Thispaperisorganizedasfollows.TheMIMprocessisdescribedinSection2.InSection3theDoEisintroduced.Thecollectionofexperimentaldataisexplainedinsection4followedbyresultsanddata

analysisinsection5.Thediscussionofresultsispresentedinsection6.Finallythepaperendswithconclusionsgiveninsection7.

2.MicroInjectionMoulding（MIM）

Micro-injectionmoulding[1]isarelativelynewtechnologyinthemanufacturingworld,andassuch,itneedstobethoroughlyinvestigated.AccordingtoMicro-powderinjectionmoulding,conductedbyLiuet.

al.[2],micro-systemtechnologywerewidelyusedinthenew21stcenturybecauseofitssuccessfulapplicationsinmanydifferentfields,e.g.influidic,medical,opticalandtelecommunications.Presentedwithmass

productioncapabilityandlowcomponentcost,maketheMIMtechnologytobeoneofthekeyproductionprocessesformicromanufacturing.TheComponentsofMIMfallintooneofthefollowingtwocategories:

TypeA:

Overallsizelessthan1mm

TypeB:

Microfeaturelessthan200um.

InitialworkonDoEanddataanalysisonMIM,conductedbyShaet.al.[3],primarilyfocusedontheanalysisof5differentfactors（themeltandmould

temperature,injectionspeed,pressureandflowstatus）affectingtheachievableaspectratiosinthreedifferentpolymermaterials.Theaspectratioistheratioofalongerdimensiontoitsshorterdimensionofaspeciallydesignedmicrofeatureforthisexperiment.TheirstudyconcludedthatMeltTemperature（Tb）andInjectionSpeed（Vi）werethekeyfactorsaffectingtheaspectratiosachievableinreplicatingmicrofeaturesinallthreepolymersmaterials.

TheeffectoftoolsurfacequalityinMIM,conductedbyGriffithset.al.[4],primarilyfocusedonthefactorsaffectingtheflowbehaviorandalsotheinteraction

betweenthemeltflowandthetoolsurface.

Thefindingsoftheseearlierinvestigationsaretakenintoconsiderationinthisstudy.

Fig1showsapictureofaMIMmachine.TheplanningofDoEandthedataanalysiswascarriedoutusingthestatisticalsoftwarepackage“Minitab16”.

3.DesignofExperiments（DoE）

ThetechniqueofdefiningandinvestigatingallpossibleconditionsinanexperimentinvolvingmultiplefactorsisknownastheDesignofExperiments.

ThetwotypesofDoEthatarewidelyusedaretheFactorialdesignandTaguchiMethod.AccordingtoMinitabdesignofexperiment[6],Factorialdesignisa

typeofdesignedexperimentthatallowsforthesimultaneousstudyoftheeffectsthatseveralfactorsmayhaveonaresponse.Whenperforminganexperiment,varyingthelevelsofallfactorssimultaneouslyratherthanoneatatime,allowsforthestudyofinteractionsbetweenthefactors.

Inafullfactorialexperiment,responsesaremeasuredatallcombinationsoftheexperimentalfactorlevels.Thecombinationsoffactorlevelsrepresenttheconditionsatwhichresponseswillbemeasured.Eachexperimentalconditioniscalled“run”andtheresponsemeasurementanobservation.Theentiresetofrunsisthe“design”.

Tominimizetimeandcost,itispossibletoexcludesomeofthefactorlevelcombinations.Factorialdesignsinwhichoneormorelevelcombinationsareexcludedarecalledfractionalfactorialdesigns.

Fractionalfactorialdesignsareusefulinfactorscreeningbecausetheyreducethenumberofrunstoamanageablesize.Therunsthatareperformedareaselectedsubsetorfractionofthefullfactorialdesign.ButRoy[7]mentionsthatusingfullfactorialandfractionalfactorialDoEmaycontributetothefollowingissues:

●Theexperimentsbecomeunwieldyincostand

timewhenthenumberofvariableislarge;

●Twodesignsforthesameexperimentmayyield

differentresults;

●Thedesignsnormallydonotpermit

determinationofthecontributionofeachfactor;

●Theinterpretationofexperimentwithalarge

numberoffactorsmaybequitedifficult.

Hence,Taguchimethodwasdevelopedinordertoovercomesomeoftheseissues.Taguchimethodisthetechniqueofdefiningandinvestigatingallpossibleconditionsinanexperimentinvolvingmultiplefactors.

TaguchimethodwasfirstintroducedbyDr.GenichiTaguchiaftertheSecondWorldWar[8,9].Hecameupwiththreebasicconcepts[7]:

1.Qualityshouldbedesignedintotheproductandnotinspectedintoit.

2.Qualityisbestachievedbyminimisingthedeviationfromatarget.Theproductshouldbesodesignedthatitisimmunetouncontrollableenvironmentalfactors.

3.Thecostofqualityshouldbemeasuredasafunctionofdeviationfromthestandardandthelossesshouldbemeasuresystem-wide.

Dr.TaguchisetupathreestageprocesstoachievetheenhancementofproductqualitybyDoEbasedupontheconceptsabove,namely,Systemdesign,Parameter

design,andTolerancedesign.

Forthefirststage,systemdesignistodeterminethesuitableworkinglevelsofdesignfactors.Itincludesdesignandtestofasystembasedonselectedmaterials,

partsandnominalproduct/processparameters.

Parameterdesignisforfindingthefactorlevelthatcanachievethebestperformanceoftheproduct/process.

Thelaststagewhichisthetolerancedesignistodecreasethetoleranceoffactorswhichissignificantlyaffectingtheproduct/process.

AspecialsetofarrayscalledOrthogonalArrays（OAs）wereconstructedtolayouttheexperiment.TheOAsimplifytheexperimentdesignprocess.Itisdoneby

selectingthemostsuitableOA,assigningthefactorstotheappropriatecolumns,anddescribingthecombinationsoftheindividualexperimentscalledthetrialconditions.

InthisstudyafractionalfactorialDoEwasconductedincombinationwithTaguchi’designconceptsforqualityenhancement.

4.CollectionofExperimentalData

Theexperimentwasdesignedandset-upasdefinedbySha,et.al.[10].Thisaimofthisexperimentistoanalysetheeffectsofsixfactorsontheachievableaspectratiosandfindthemostsignificantfactorsinordertoreachtheoptimalsettingswhichwouldgivethehighestaspectratios.Fig.2showsthetestpartwithmicrofeaturesintheformoflegswithtwolevelofwidth（W）,200or500um,anddepth（D）,700（）or100um（）wherethefeatureshavingthesamedepth,D1orD2,weregroupedononesideofthepart.

Threedifferentmaterials,namely,semi-crystallinepolymerssuchaspolypropylene（PP）,polyoxymethylene（POM）andanamorphouspolymersuchasacrylonitrilebutadiene-styrene（ABS）wereinthisstudy.Theparametersinvestigatedwerebarreltemperature（Tb）,mouldtemperature（Tm）,injectionspeed（Vi）,holding

pressure（Ph）,theexistenceofairevacuation（Va）andthewidth（W）ofmicro-legs.

Theaspectratios,i.e.theratiosbetweenthelengthofthemicrofeatureandtheirdepths,D1orD2,aremeasuredduringtheexperiment.Theaveragevaluesof24measuredresponseswiththesameWandD（twoperpart）whileapplyingtheprocesssettinggiveninTable1areusedinthisstudy.

5.ResultsandDataAnalysis

A2-levelsixfactorsfractionalfactorialdesign（26-2）wasappliedinthisexperiment.TheDoEwasusedtoidentifythefactorsthatwereactiveandsignificanttostudythefillingofmicrochannels.ThepurposeofthisexerciseistolookattheresultsoftheDoEresponsesinordertounderstandtheprocessandselectthesignificantfactorswiththeirappropriatesettingswhicharenecessaryforoptimalperformance.

5.1.Results

ThemeasuredexperimentalresponsesfortheDoEfortheratiosbetweenthelengthofthemeltfillsandthedepthofthechannels,D1orD2arerecordedinTable2.ThevalueofD1andD2shownonthetablearetheaveragevaluesof24measurements.

5.2.DataAnalysis

Thestatisticalsoftwarepackage“Minitab16”wasusedtoanalysetheresultsobtainedfromtheexperiment.TheresultoftheanalysisforPPforboththecasesofD1andD2isgiveninTable3.

InTable3the“Effect”columnshowsthepositiveornegativeeffectofthefactoronthemeasuredresponse.Hencethehighertheeffectthemoresignificantthefactorinconsiderationwillbe.The“effect”columndeterminesthefactors’relativestrength,the“p-values”determinewhichofthefactorsarestatisticallysignificant.InthisstudythevaluesinthePcolumnoftheEstimatedEffectsandCoefficientstableareusedtodeterminewhichoftheeffectsaresignificant.Tomakeadecisionconcerningwhichfactorsaresignificant,furtheranalysisisnecessaryandthiswillbediscussedinthenextsection.Atypicalvalueforthesignificancewaschosentobe0.05throughoutthisstudy.

6.DiscussionofResults

TheaboveresultswereutilisedtoproducemoreevidencetosupporttheclaimsforstrongfactorswhichmatterthemostfortheMIMprocess.

Using=0.05,forPPD1,thep-valuesfoundforTbis0.038andViis0.009indicatethatthemaineffectsfromthesetwosinglefactorsTbandViaresignificant,i.e.theirp