SPC - AIAG Manual

STATISTICALPROCESSCONTROLWC)REFERENCEMANUALIssued1992,SecondPrintingMarch1995(newcoveronly)Copyright01992,O1995ChryslerCorporation,FordMotorCompany,andGeneralMotorsCorporationSelectionProcedurefortheUseoftheControlChartsDescribedinThisManualDETERMINECHARACTERISTICTOBECHARTEDNONCONFORMlTlESYESCONDUCIVETOSUBGROUPSAMPLING-e.g.,CHEMICALYESUSECHARTFORINDIVIDUALS:X-MRNote:Thischartassumesthemeas-urementsystemhasbeenassessedandisappropriateFOREWORDThisReferenceManualwaspreparedbythequalityandsupplierassessmentstaffsatChrysler,FordandGeneralMotors,workingundertheauspicesoftheAutomotiveDivisionoftheAmericanSocietyforQualityControlSupplierQualityRequirementsTaskForce,incollaborationwiththeAutomotiveIndustryActionGroup.TheASQCIAIAGTaskForcecharteristostandardizethereferencemanuals,reportingformatsandtechnicalnomenclatureusedbyChrysler,FordandGeneralMotorsintheirrespectivesupplierassessmentsystems:SupplierQualityAssurance,TotalQualityExcellenceandTargetsforExcellence.Accordingly,thisReferenceManualcanbeusedbyanysuppliertodevelopinformationrespondingtotherequirementsofeitherChrysler’s,Ford’sorGeneralMotors’supplierassessmentsystems.Untilnow,therehasbeennounifiedformalapproachintheautomotiveindustryonstatisticalprocesscontrol.Certainmanufacturersprovidedmethodsfortheirsuppliers,whileothershadnospecificrequirements.Inanefforttosimplifyandminimizevariationinsupplierqualityrequirements,Chrysler,Ford,andGeneralMotorsagreedtodevelopand,throughAIAG,distributethismanual.TheworkteamresponsiblefortheManual’scontentwasledbyLeonardA.BrownofGeneralMotors.Themanualshouldbeconsideredanintroductiontostatisticalprocesscontrol.ItisnotintendedtolimitevolutionofstatisticalmethodssuitedtoparticularprocessesorcommoditiesnorisitintendedtobecomprehensiveofallSPCtechniques.Questionsontheuseofalternatemethodsshouldbereferredtoyourcustomer’squalityactivity.TheTaskForcegratefullyacknowledges:theseniorleadershipandcommitmentofVicePresidentsThomasT.StallkampatChrysler,ClintonD.LaueratFord,andDonaldA.PaisatGeneralMotors;thetechnicalcompetenceandhardworkoftheirqualityandsupplierassessmentteams;andtheinvaluablecontributionsoftheAutomotiveIndustryActionGroup(underAIAGExecutiveDirectorJosephR.Phelanlinthedevelopment,productionanddistributionofthisReferencemanual.WealsowishtothanktheASQCreadingteamledbyTrippMartinofPetersonSpring,whoreviewedtheManualandintheprocessmadevaluablecontributionstointentandcontent.BruceW.PinceTaskForceCoordinatorSandyCorporationTroy,MichiganDecember,1991ThisManualiscopyrightedbyA.I.A.G.,allrightsreserved,1991.AdditionalcopiescanbeorderedfromA.I.A.G.,and/orpermissiontocopyportionsoftheManualforusewithinsupplierorganizationsmaybeobtainedfromA.I.A.G.at(313)358-3570.ACKNOWLEDGEMENTThejointconsensusonthecontentsofthisdocumentwaseffectedthroughTaskTeamSubcommitteeMembersrepresentingGeneralMotors,Ford,andChrysler,respectively,whoseapprovalsignaturesappearbelow,andwhogratefullyacknowledgethesignificantcontributionofPeteJessupoftheFordMotorCompany,whowasresponsiblefordevelopingthemajorityofthematerialfoundinChaptersI,II,andIII,andtheAppendixofthisdocument.HarveyGoltzeroftheChryslerCorporationcontributedconceptsrelativetoprocesscapabilityandcapabil-itystudies,foundintheintroductionsectionofChapterI.JackHermanofDuPontcontributedsomeoftheconceptsrelativetocapabilityandperformanceindicesandtheimportanceofmeasurementvariability,foundinportionsofChaptersIIandIV,respectively.TheGeneralMotorsPowertrainDivisioncontributedthediscussionandexamplesrelativetosubgroupingandprocessoveradjustment.ThesectioninChapterIIwhichprovidesunderstandingofprocesscapabilityandrelatedissueswasdevelopedbytheGeneralMotorsCorporateStatisticalReviewCommittee.ThiscommitteealsocontributedtothedevelopmentofChapterIV,ProcessMeasurementSystemsAnalysis,aswellastosomeAppendixitems.Finally,valuableinputtoallsectionsofthemanualwasprovidedbyASQCrepresentativesGregGruska,DougBerg,andTrippMartin.LeonardA.Brown,G.M.VictorW.Lowe,Jr.,FordDavidR.Benham,ChryslerDecember1991TABLEOFCONTENTSChapterIINTRODUCTIONTOCONTINUALIMPROVEMENTANDSTATISTICALPROCESSCONTROL...............................1Section1PREVENTIONVERSUSDETECTION.....................5Section2APROCESSCONTROLSYSTEM.........................7Section3VARIATION:COMMONANDSPECIALCAUSES............9Section4LOCALACTIONSANDACTIONSONTHESYSTEM.........11Section5PROCESSCONTROLANDPROCESSCAPABILITY.........13Section6THEPROCESSIMPROVEMENTCYCLEANDPROCESSCONTROL...................................17Section7CONTROLCHARTS:TOOLSFORPROCESSCONTROL....21Section8BENEFITSOFCONTROLCHARTS.......................25ChapterIICONTROLCHARTFORVARIABLES...............................27Section1AVERAGEANDRANGECHARTS(KANDR1.............29A.GATHERDATA..........................................31B.CALCULATECONTROLLIMITS...........................37C.INTERPRETFORPROCESSCONTROL.....................39D.INTERPRETFORPROCESSCAPABILITY..................57Section2AVERAGEANDSTANDARDDEVIATIONCHARTS(KANDs).............................................65A.GATHERDATA...................