>> P.530
thevaluesthatdividesrangebetweenHistogramtheminimumAdiagrammeasurementvalues(appearancefrequency)ineachdivisionintheformofabargraph.Thismakesiteasiertounderstandtheroughaverageortheapproximateextentofdispersion.Adiagramindicatingasymmetricalbell-shapeddistributionshowswhatiscalled“normaldistribution.”themaximumandseveraldivisionsthenumberofshowsintoandProcessCapabilityProcess-specicperformancedemonstratedwhenthefollowingconditionsaremet:•Theprocessissufcientlystandardized,•Anycausesofmalfunctionsareeliminated,•Theprocessisinastateofstatisticalcontrol.Theprocesscapabilityisrepresentedbymean±3or6whenthequalitycharacteristicoutputfromtheprocessshowsnormaldistribution.Thisindicatesstandarddeviation.ProcessCapabilityIndex(PCorCp)Theindexvalueiscalculatedbydividingthetoleranceofatargetcharacteristicbytheprocesscapability(6).Thevaluecalculatedbydividingthedifferencebetweenthemean(X)andthestandardvalueby3maybeusedtorepresentthisindexincasesofaunilateraltolerance.Theprocesscapabilityindexassumesthatacharacteristicfollowsthenormaldistribution.Note:Ifacharacteristicfollowsthenormaldistribution,99.74%dataiswithintherange±3fromthemean.BilateraltoleranceCp=USL-LSL6×σUSL:UpperspecicationlimitLSL:LowerspecicationlimitUnilateraltolerance...IfonlytheupperlimitisstipulatedCp=USL-X3×σUnilateraltolerance...IfonlythelowerlimitisstipulatedCp=X-LSL3×σSpecicexamplesofaprocesscapabilityindex(Cp)(bilateraltolerance)LSLUSLQualityControl(QC)Methodsandtheirsystemforeconomicallyproducingproductsorservicesofaqualitythatmeetscustomerrequirements.ProcessQualityControlActivitiestocontrolthemanufacturingprocess,reduceproductvariation,andkeepproductvariationlow.Processimprovementandstandardizationaswellastechnologyaccumulationarepromotedthroughtheseactivities.StatisticalProcessControl(SPC)Processqualitycontrolthroughstatisticalmethods.PopulationPopulationAgroupofallitemsthathavecharacteristicstobeconsideredforimprovingandcontrollingprocessesandqualityofproduct.Ordinarily,thepopulationisthegroupthatisgoingtobehandledbasedonasample.LotCollectionofproductproducedunderthesameconditions.SampleAnitemofproduct(oritems)takenoutofthepopulationtoinvestigateitscharacteristics.SampleSizeNumberofproductitemsinthesample.BiasValuemeasurementvalueswhenmultiplemeasurementsareperformed.subtractingcalculatedvaluefromtruethethebymeanofinDispersion,ImprecisionVariationvalue.Standarddeviationvaluesaroundthemean.thevaluesofaisusuallyusedtorepresenttargetcharacteristicinrelationtothemeanthedispersionofQualityControlTheprocesscapabilityisbarelyachievedasthe6sigmaprocesslimitsarecoincidentwiththetolerancelimits.USL668Cp=1LSLNoncomplianceMeasuredvaluesLSLUSL610BiasDispersion/imprecisionTolerance(USL-LSL)13-3Upperspecificationlimit(USL)σMeanTargetprocessmeanLowerspecificationlimit(LSL)FrequencyGeneralTerminMeasurement:QualityControl
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