规范RR产业技术GaugeRRIndustrytechnology

TheOfficialElectronicPublicationoftheNationalAssociationofIndustrialTechnology•©2007GaugeR&R:AnEffectiveMethodologyforDeterminingtheAdequacyofaNewMeasurementSystemforMicron-levelMetrologybyDr.DavidW.HoffaandDr.ChadLauxVolume23,Number4-October2007throughDecember2007Peer-RefereedArticleLeanManufacturing/SixSigmaMetrologyQualityQualityControlResearchMethodsStatisticalMethodsKEYWORDSEARCH2JournalofIndustrialTechnology•Volume23,Number4•October2007throughDecember2007•:AnEffectiveMethodologyforDeterminingtheAdequacyofaNewMeasurementSystemforMicron-levelMetrologybyDr.DavidW.HoffaandDr.ChadLauxDr.DavidHoffaisaQualityEngineerforAccumold®,the“worldleadersinMicro-Mold®manufacturingsolu-tions,”basedinAnkeny,Iowa.Heisresponsibleforcontinuousmetrological,organizational,andproductqualityimprovementthroughtheapplicationofsound,statisticalmethodsandLeanManufacturingconcepts.HewasawardedhisPh.D.inIndustrialTechnologyfromIowaStateUniversityin2006.HeisaCertifiedSeniorIndustrialTechnologistandthe2005recipientoftheNAITFoundation’sDr.CloisE.KicklighterDoctoralStudentScholarshipAward.AbstractAsengineeringtolerancesapproachthesubmicronrangeandcustomerdemandsforstatisticallyverifiedqual-itylevelsincrease,Accumold,ahighlyspecialized,high-techmanufacturerofinjectionmoldedlead-frameandsmall-andmicro-scaleplasticparts,hasrealizedacriticalneedforanimprovedmeasurementsystem.Manymeasure-menttechnologies(includingconfocalanddynamicrangelasers,scanningelectronmicroscopes,whitelightinter-ferometers,andprecisionvideo)frommanufacturersaroundtheworldwereexplored.TheANOVA-based“GaugeR&R”(RepeatabilityandReproduc-ibility)studywasemployedasthemainanalyticaltoolfordeterminingtheefficacyofapotentialmeasure-mentsystem;factorslikepotentialforautomation,easeofuseandprogram-ming,andshopfloorrobustnesswereconsidered.TheGaugeR&Rstudieseffectivelyprovidedmanagementwithquantitativemeasuresfordetermin-ingwhetheracandidatesystemwasadequateformeasuringthecriticalfeatureofinterest,whichwasa10±2microndifferencebetweenadjacentstepheights,andasaresult,Accumoldhaspurchasedanewmulti-sensorsystemcapableofachievingaprecisiontotoleranceratio(a.k.a.GaugeCapa-bilityRatio,studyvariancetotoleranceratio,etal.)of11%andresolvingupto74distinctcategorieswhenmeasuringthesefeatures.IntroductionTocompeteinaglobalmarketplace,manufacturersareincreasinglyturningtoadvancedmanufacturingtechniquestoincreaseproductivityandgainacompetitiveadvantage.Thistrendre-quiresmanagementtobeabletomakedecisionsbasedonproperquantitativeanalysisofdata.Inthemanufacturingprocess,controlofvariationwithanincreasinglyhighdegreeofprecisiondemandsanimproveddegreeofmea-surementeffectiveness.MeasurementSystemsAnalysis(MSA)isacollectionofstatisticalmethods(whichincludestheGaugeRepeatabilityandRepro-ducibilitystudy)fortheanalysisofmeasurementsystemcapability(Auto-motiveIndustryActionGroup[AIAG],2002;Smith,McCrary,&Callahan,2007).Accumold1,ahighlyspecialized,high-techmanufacturerofinjectionmoldedlead-frameandsmall-andmicro-scaleplasticparts,hadrealizedaneedforanimprovedmeasurementsystemasaresultofanewcustomerdemandforacritical-to-functionfeatureofadifferenceof10±2microns(394±79millionthsofaninch)betweentwoadjacentstepheights.ThisparticularcustomeralsodemandedthatanANO-VA-basedGaugeRepeatabilityandReproducibilitystudybeperformedandtheresultoftheaccompanyingpreci-siontotoleranceratio(P/T)exhibitlessthan30%error,perMSAtechniquesDr.ChadLauxisaVisitingAssistantProfessorintheIndustrialTechnologyDepartmentatPurdueUniversityinAnderson,Indiana.Heteachescoursesinindustrialorganization,statistics,andergonomics.Hisresearchinterestsincludeadvancedmanufacturing,agriculturebiotechnology,andqualityprocessimprovement.HeisacertifiedSixSigmaBlackbeltfromGeneralElectricCo,CaterpillarInc,andtheAmericanSocietyforQuality.HeisaNAITCertifiedSeniorIndustrialTechnologistandthe2007recipientoftheSilvius-WolanskyDoctoralFel-lowshipAwardfromtheDepartmentofAgricultureandBiosystemsEngineeringatIowaStateUniversity.1Accumold®isaregisteredtrademarkofAccu-MoldLLC.3JournalofIndustrialTechnology•Volume23,Number4•October2007throughDecember2007•(AIAG,2002;Smith,McCrary,&Cal-lahan,2007).Forillustration’ssake,letusfirstcon-sidertherequirementof10±2µm.Thethicknessofahumanhairisapproxi-mately90µm;therefore,notonlyisthisspecificationaskingAccumoldtoinjectionmoldfeaturesintoplasticpartswhichare1/9ththethicknessofahumanhair,theyarealsodemandingthatAc-cumoldmaintaintotaltoleranceonthatfeatureequivalenttothethicknessofonesliverofahumanhairwhichhasbeensplitalongitslength22times!ReviewofLiteratureMeasurementSystemsAnalysisMeasurementSystemsAnalysisDemingoncestatedthatknowledgeofvariationwasoneofthemostpower-fultoolsacompanycouldapplyinthequestforimprovement(Joiner&Gaud-ard,1990).Becausevariationisinher-entinaprocessandisunpredictable,strategiestominimizevariationarecommoninmanufacturing(McGhee,1985;MacKay&Steiner,1997).Un-derstandingtheindividualcomponentsofprocessvariation(measurementsys-temvariation,inparticular)iscriticaltothispr