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1、ProcessCapability Cp Cpk Pp Ppk GlobalTrainingMaterial Creator GlobalMechanicsProcessManagerFunction MechanicsApprover GaryBradley GlobalProcessTeamDocumentID DMT00018 ENVersion Status V 1 0 ApprovedLocation Notes NMP DOCMANR4 PCP PCProcessLibraryDocManChangeHistory IssueDateHandledByComments1 021st
2、Dec 01JimChristy S renLundsfrydApprovedforGlobalUseNOTE Allcommentsandimprovementsshouldbeaddressedtothecreatorofthisdocument Contents SectionHeading DescriptionPage1Variation TolerancesandDimensionalControl42Population SampleandNormalDistribution153CpandCpkConcept284UseoftheNMPDataCollectionSpreads
3、heet445ConfidenceofCpk52 ProcessCapability EvaluatingManufacturingVariation AcknowledgementsBennyMatthiassen NMPCMT Copenhagen Denmark FrankAdler NMPAlliance Dallas USA JoniLaakso NMPR D Salo Finland JimChristy NMPSRC Southwood UK Section1Variation TolerancesandDimensionalControl TwoTypesofProductCh
4、aracteristics Variable Acharacteristicmeasuredinphysicalunits e g millimetres volts amps decibelandseconds Inthistrainingwedealwithvariablesonly TheSourcesofProcess SystemVariation Process TwoTypesofProcesses Allprocesseshave Natural random variability duetocommoncauses StableProcess Aprocessinwhich
5、variationinoutcomesarisesonlyfromcommoncauses UnstableProcess Aprocessinwhichvariationisaresultofbothcommonandspecialcauses Unnaturalvariability duetospecialcauses Shewhart 1931 TheTwoCausesofVariation CommonCauses Causesthatareimplementedintheprocessduetothedesignoftheprocess andaffectalloutcomesof
6、theprocessIdentifyingthesetypesofcausesrequiresmethodssuchasDesignofExperiment DOE etc SpecialCauses Causesthatarenotpresentintheprocessallthetimeanddonotaffectalloutcomes butarisebecauseofspecificcircumstancesSpecialcausescanbeidentifiedusingStatisticalProcessControl SPC Defect USL LSL nominalvalue
7、 Tolerances LSL lowerspecificationlimit 10 7 USL upperspecificationlimit 10 9 Acceptablepart RejectedPart RejectedProduct Nominal10 8 0 1 RejectedPart Atoleranceisaallowedmaximumvariationofadimension MeasurementReport Inmostcaseswemeasureonlyonepartpercavityformeasurementreport ExampleofCapabilityAn
8、alysisData Forsomecriticaldimensionsweneedtomeasuremorethan1partForcapabilitydataweusuallymeasure5pcs2times hour 100pcs butsamplingplanneedstobemadeonthebasisofproductionquantity rundurationandcycletime ProcessCapability Whatisit ProcessCapabilityisameasureoftheinherentcapabilityofamanufacturingproc
9、esstobeabletoconsistentlyproducecomponentsthatmeettherequireddesignspecifications ProcessCapabilityisdesignatedbyCpandCpk ProcessPerformanceisameasureoftheperformanceofaprocesstobeabletoconsistentlyproducecomponentsthatmeettherequireddesignspecifications ProcessPerformanceincludesspecialcausesofvari
10、ationnotpresentinProcessCapability ProcessPerformanceisdesignatedPpandPpk WhyMakeProcessCapabilityStudies Aprocesscapabilitystudywouldrevealthatthetoolshouldnotbeaccepted Whenadimensionneedstobekeptproperlywithinspec wemuststudytheprocesscapability butstillthisisnoguaranteefortheactualperformanceoft
11、heprocessasitisonlyaninitialcapabilitystudy TheNokiaProcessVerificationProcess Section2 Population SampleandNormalDistribution TheBellShaped Normal Distribution Symmetricalshapewithapeakinthemiddleoftherangeofthedata Indicatesthattheinputvariables X s totheprocessarerandomlyinfluenced PopulationPara
12、meters Populationmean Populationstandarddeviation PopulationversusSample PopulationAnentiregroupofobjectsthathavebeenmadeorwillbemadecontainingacharacteristicofinterest SampleThegroupofobjectsactuallymeasuredinastatisticalstudyAsampleisusuallyasubsetofthepopulationofinterest TheNormalDistribution Wh
13、atMeasurementsCanBeUsedtoDescribeaProcessorSystem mean average ordescribesthelocationofthedistribution m ameasureofcentraltendency isthemeanoraverageofallvaluesinthepopulation Whenonlyasampleofthepopulationisbeingdescribed meanismoreproperlydenotedas x bar Themostsimplemeasureofvariabilityistherange
14、 Therangeofasampleisdefinedbyasthedifferencebetweenthelargestandthesmallestobservationfromsamplesinasub group e g 5consecutivepartsfromthemanufacturingprocess WhatMeasurementsCanBeUsedtoDescribeProcessvariation sST oftennotatedas orsigma isanothermeasureofdispersionorvariabilityandstandsfor short te
15、rmstandarddeviation whichmeasuresthevariabilityofaprocessorsystemusing rational sub grouping whereistherangeofsubgroupj Nthenumberofsubgroups andd2 dependsonthenumberNofsubgroupsandthesizenofasubgroup seenextslide WhatMeasurementsCanBeUsedtoDescribeProcessvariation d2 valuesforSST Example WhatMeasur
16、ementsCanBeUsedtoDescribeProcessvariation TheDifferenceBetweenSSTandsLT ThedifferencebetweenthestandarddeviationssLTandsSTgivesanindicationofhowmuchbetteronecandowhenusingappropriateproductioncontrol likeStatisticalProcessControl SPC Short termstandarddeviation Long termstandarddeviation ThedifferencebetweensSTandsLT ThedifferencebetweensSTandsLT ThedifferencebetweensLTandsSTisonlyinthewaythatthestandarddeviationiscalculatedsLTisalwaysthesameorlargerthansSTIfsLTequalssST thentheprocesscontrolove
