SPC_Training

120/08/2019SPCtraining220/08/2019BeginningsofSPCDr.WalterShewhartpioneeredIndustrialControl(SPC)inthe1920’s&30’s.TheU.S.usedindustrialcontrolverysuccessfullyduringWWII.Afterthewar,U.S.industriesdroppedindustrialcontrolinfavorofareturntomassproduction.Japan,devastatedbythewar,adoptedtheteachingsofDr.W.EdwardsDemingandDr.JosephM.Juran.Japanesecompaniescontinuedtodeveloptoolsforprocesscontrolsuchascompanywidequalitycontrolandqualitycircles,the7QualityToolsandthe7ManagementandPlanningTools320/08/2019DefinitionofQuality“Fitnessforpurposeoruse”(Juran).“Thetotalityoffeaturesandcharacteristicsofaproductorservicethatbearonitsabilitytosatisfystatedorimpliedneeds”(ISO8402:1986).Manufacturingbased-Qualityisdefinedasthedesirableoutcomeofengineeringandmanufacturingpractice,orconformancetospecifications420/08/2019WhatisaProcess?Thetransformationofasetofinputs(materials,methods,operations)intoasetofoutputs(products,information,services-moregenerally-results)ProcessMaterialsMethods/ProceduresInformation(includingspecifications)People(skills,training,knowledge)EnvironmentRecordsEquipment(tools,plant)FeedbackThevoiceoftheprocess(SPC)INPUTSOUTPUTSProductsServicesInformationPaperworkSUPPLIERSCUSTOMERSFeedbackThevoiceofthecustomer520/08/2019WhatisControl?Controlreferstothemeasurementsoftheperformanceofaprocessandfeedbackrequiredforcorrectiveaction.Aprocessissaidtobeoperatinginastateofstatisticalcontrolwhencommoncausesaretheonlysourceofvariation.Statisticalcontrolisnotanaturalstateformostprocesses—Itisanachievement,onebyone,specialcauseeliminationTheinitialfunctionofaprocesscontrolsystemistoprovideastatisticalsignalwhenspecialcausesofvariationarepresent,andtoavoidgivingfalsesignalswhentheyarenotpresent620/08/2019QualityToolKitStatisticalProcessControl(SPC)isamethodologywhichusesthebasicgraphicalandstatisticaltoolstoanalyze,controlandreducevariabilitywithinaprocessSPCusesanumberofbasicqualitytoolsRunChartHistogramControlChartDistributionsandconfidenceintervals(Capability)720/08/2019TheSPCSystemAsystematicapproachtoansweringthefollowingquestionsCanwedothejobcorrectly?(capability)Arewedoingthejobcorrectly?(control)Havewedonethejobcorrectly?(qualityassurance)Couldwedothejobbetter?(improvement)EnhancesprocesscontrolRequiresempoweredemployees820/08/2019SourcesofVariationVariationisafactofnatureandafactoflifeCommoncausevariation-withintheprocesstheyareinherentinanyprocessallthetime(partofsystemdesign:equipmentdesign,materialcharacteristics,inspectionmethods,maintenance)theirimpactvariesfromdaytodayindividuallycommoncauseshaveaslighteffectonvariationcollectively,commoncausescanadduptosignificantvariationaccountforabout80to90percentoftheobservedvariationSpecialcausevariation-outsidetheprocessspecialcausesappearsporadicallyinaprocesstheyoriginateoutsidetheprocess(badbatchofmaterial,poorlytrainedoperator,excessivetoolwear,notfollowingprocedure,overadjustment)cancontributeasmallamountorlargeamountofvariationbuttypicallyhaveamuchbiggerimpactthananyonecommoncause920/08/2019SpecialCause–CommonCause34115FilledHologramAreaUChart;variable:HologramDefectsU:.03917(.03917);Sigma:.02799(.02799);n:50.102030405060708090-0.020.000.020.040.060.080.100.120.140.160.0000.03917.12313Statistics(Samples):Mean=.03917SpecialCauseCommonCause1020/08/2019PrecisionandAccuracyPrecision-thedegreeofthespreadofthevaluesinaprocessAccuracy-theabilityofaprocesstohitthetargetvalue1120/08/2019PrecisionandAccuracyTrueValue1234512345TrueValueTrueValueNotpreciseandnotaccuratePrecisebutnotaccurateTrueValue12345AccuratebutnotpreciseAccurateandprecise1220/08/2019PrecisionandAccuracyProcesscharacterizationThedistinctionbetweenprecisionandaccuracycanonlybeassessedbylookingatanumberofresultsorvalues,notlookingatindividualoneTamperingMakingdecisionsaboutadjustmentstobemadetoaprocessonthebasisofoneindividualresultmaygiveanundesirableoutcomeduetolackofinformationaboutaccuracyandprecisionSpecialcausebeforecommoncauseTheadjustmenttocorrectlackofprocessaccuracy(specialcause)islikelytobe‘simpler’thanthelargerinvestigationusuallyrequiredtounderstandorcorrectproblemsofspreadorlargevariation(commoncause)1320/08/2019MeasuresofAccuracyorCenteringMean/Median/ModeMeasureofcentering-meanniinnxnxxxxX1321...Differencebetweenmean,medianandmodeMode-MostfrequentvalueMedian-middlevalueMean-averagevalue1420/08/2019ArithmeticMeanThesamplemeanisthemeasureofcentraltendencythatmostaccuratelyreflectsthepopulationmeanVerysensitivetoextremescoresDefinedasthepointatwhichthesumofthedeviationsfromthemeanequalstozero.0)1,0,1()4(5,4,3isdeviationstheofsumTheofmeanScoreExample:1520/08/2019MedianThepointatwhichonehalf,or50%ofthescoresfallaboveandonehalf,or50%,fallbelow(50thpercentile).Listthevaluesinorder,eitherfromhighesttolowestorlowesttohighest.FindthemiddlemostscoreWhenthereisanevenamountofscores,themedianissimplytheaveragebetweenthetwomiddlevaluesExample:084,36500,34668,37500,25456,32500,34668,37365,54456,135andofaveragemedian1620/08/2019ModeThemodeisthevaluewhichoccursmostfrequentlyListallofthevaluesi