SPCAttribute Control Charts.ppt

AttributeControlCharts,LearningObjectives,DefectivevsDefectBinomialandPoissonDistributionpChartnpChartcChartuChartTestsforInstability,ShewhartControlCharts-Overview,DefectiveandDefect,DefectiveAunitofproductthatdoesnotmeetcustomersrequirementorspecification.Alsoknownasanon-conformingunit.ExampleAbasecastingthatfailsporosityspecificationisadefective.Adiscclampthatdoesnotmeettheparallelismspecificationisadefective.,DefectAflaworasinglequalitycharacteristicthatdoesnotmeetcustomersrequirementorspecification.Alsoknownasanon-conformity.Therecanbeoneormoredefectsinadefective.ExampleAdentonaVCMpolethatfailscustomersspecificationisadefect.Astainonacoverthatfailscustomer中国最大的资料库下载,DefectiveandDefect,ShewhartControlChartsforAttributeData,Thereare4typesofAttributeControlCharts:,43,np,c,p,u,Defects,(PoissonDistribution),Defectives,(BinomialDistribution),TypesofDataandDistributions,DiscreteData(Attribute)BinomialPoissonContinuousData(Variable)NormalExponentialWeibullLognormaltc2F,DiscreteDistributions,ContinuousDistributions,TypesofDistributions,NormalDistribution,ExponentialDistribution,UniformDistribution,BinomialDistribution,DiscreteDistributions,ContinuousDistributions,BinomialDistributionUsefulforattributedata(orbinarydata)Resultfrominspectioncriteriawhicharebinaryinnature,e.g.pass/fail,go/nogo,accept/reject,etc.Datageneratedfromcountingofdefectives.,DiscreteDistributions,PlotisknownasProbabilityMassFunctionofX,BinomialDistributionIfaprocesstypicallygives10%rejectrate(p=0.10),whatisthechanceoffinding0,1,2or3defectiveswithinasampleof20units(n=20)?,DiscreteDistributions,CommonlyusedinAcceptanceSampling,Thelocation,dispersionandshapeofabinomialdistributionareaffectedbythesamplesize(n)anddefectiverate(p).,BinomialDistribution,DiscreteDistributions,JamesBernoulli,BinomialDistribution,DiscreteDistributions,PoissonDistributionUsefulfordiscretedatainvolvingerrorrate,defectrate(dpu,dpmo),particlecountrate,etc.Datageneratedfromcountingofdefects.,DiscreteDistributions,PoissonDistributionIfaprocesstypicallygives4.0defectrate(l=4dpu),whatisthechanceoffinding0,1,2or3defectsperunit?,DiscreteDistributions,Commonlyusedasanapproximationofthebinomialdistributionwhen:p10implyingnp5Forothervaluesofp,thegeneralguidelineistohavenp10togetasatisfactoryapproximationofthenormaltothebinomial.,pChart,pChart,FollowingShewhartsprinciple,theCenterLineandControlLimitsofapchartare:,Ifthesamplesizeisnotconstant,thentheControlLimitsofapchartmaybecomputedbyeithermethod:a)VariableControlLimitswhereniistheactualsamplesizeofeachsamplingib)ControlLimitsBasedonAverageSampleSizewherenistheaverage(ortypical)samplesizeofallthesamples,pChart,WhentoUseControlLimitsBasedonAverageSampleSizeinsteadofVariableControlLimitsSmallestsubgroupsize,nmin,isatleast30%ofthelargestsubgroupsize,nmax.Futuresamplesizeswillnotdiffergreatlyfromthosepreviouslyobserved.WhenusingControlLimitsBasedonAverageSampleSize,theexactcontrollimitsofapointshouldbedeterminedandexaminedrelativetothatvalueif:ThereisanunusuallylargevariationinthesizeofaparticularsampleThereisapointwhichisnearthecontrollimits.,pChart,Example1:pChart,S/NSampledRejects1501225015350845010550465077501685099501410501011505125061350171450121550221650817501018505195013205011,Frozenorangejuiceconcentrateispackedin6-ozcardboardcans.Ametalbottompanelisattachedtothecardboardbody.Thecansareinspectedforpossibleleak.20samplingsofdifferentsamplingsizewereobtained.Verifyiftheprocessisincontrol.ThedataarefoundinSPCCharts.MTW.,MiniTabsStatControlChartsP,Example1:pChart,Example1:pChart,Example1:pChart,Example1:pChart,MinitaballowsdifferencesetofcontrolchartstobeplottedononechartMiniTabsStatControlChartsP,Example1:pChart,npChart,Ifthesamplesizeisconstant,itispossibletobaseacontrolchartonthenumbernonconforming(np),ratherthanthefractionnonconforming(p).TheCenterLineandControlLimitsofannpchartare:,Example2:npChart,S/NSampledRejects1501225015350845010550465077501685099501410501011505125061350171450121550221650817501018505195013205011,Frozenorangejuiceconcentrateispackedin6-ozcardboardcans.Ametalbottompanelisattachedtothecardboardbody.Thecansareinspectedforpossibleleak.20samplingsof50cans/samplingwereobtained.Verifyiftheprocessisincontrol.ThedataarefoundinSPCCharts.MTW.,Example2:npChart,MiniTabsStatControlChartsNP,Example2:npChart,pChartvsnpChart,Foreaseofrecording,thenpchartispreferred.Thepchartoffersthefollowingadvantages:accommodationforvariablesamplesizeprovidesinformationaboutprocesscapability,SampleSizeforpandnpCharts,SampleSizeisdeterminedbasedonthe2criteria:AssumptiontoapproximateBinomialDistributiontoaNormalDistributionToensurethattheLCLisgreaterthanzero.,Forp0.5,Forp=othervalues,cChart,DefectsperUnit(DPU)ErrorRate/DefectRateDefectsperOpportunity,2,0,1,0,0,2,0,1,0,0,S,a,m,p,l,e,N,u,m,b,e,r,S,a,m,p,l,e,C,o,u,n,t,C,=,9,.,6,5,0,3,.,0,S,L,=,1,8,.,9,7,-,3,.,0,S,L,=,0,.,3,3,0,7,cChart,Eachspecificpointatwhichaspecificationisnotsatisfiedresultsinadefectornonconformity.ThecchartisacontrolchartforthetotalnumberofdefectsinaninspectionunitbasedonthenormaldistributionasanapproximationforthePoissondistribution,whichcanhappenwhen:cor15,cChart,InspectionUnitTheareaofopportunityfortheoccurrenceofnonconformities.e.g.aHSA,amedia,aPCBAThisisanentitychosenforconvenienceofrecord-keeping.Itmayconstitutemorethan1unitofproduct.e.g.aHSA,bothsurfacesofamedia,10piecesofPCBA,cChart,Ifthenumberofnonconformities(defects)perinspectionunitisdenotedbyc,then:TheCenterLineandControlLimitsofacchartare:,uChart,Incaseswherethenumberofinspectionunitsisnotconstant,theuchartmaybeusedinstead,with:Iftheaveragenumberofdefectsperinspectionunitisdenotedbyu,then,Whereciisthecountofthenumberofdefectsinnumberofinspectionunits,ai,uChart,TheCenterLineandControlLimitsofauchartare:,Example3:canduCharts,S/NUnitsDefects1510251235845145510651675118579510105151159125513571451115512165617581851019572055,Apersonalcomputermanufacturerplanstoestablishacontrolchartfornonconformitiesatthefinalassemblyline.Thenumberofno