6sigma黑带培训教材(英文)

Information,thewayyouwantitProcessCapabilityAnalysis(MeasurePhase)ScopeofModule•ProcessVariation•ProcessCapability–Specification,ProcessandControlLimits–ProcessPotentialvsProcessPerformance•Short-TermvsLong-TermProcessCapability•ProcessCapabilityforNon-NormalData–Cycle-Time(ExponentialDistribution)–RejectRate(BinomialDistribution)–DefectRate(PoissonDistribution)ProcessVariationProcessVariationistheinevitabledifferencesamongindividualmeasurementsorunitsproducedbyaprocess.SourcesofVariation•withinunit(positionalvariation)•betweenunits(unit-unitvariation)•betweenlots(lot-lotvariation)•betweenlines(line-linevariation)•acrosstime(time-timevariation)•measurementerror(repeatability&reproducibility)TypesofVariationInherentorNaturalVariation•Duetothecumulativeeffectofmanysmallunavoidablecauses•Aprocessoperatingwithonlychancecausesofvariationpresentissaidtobe“instatisticalcontrol”TypesofVariationSpecialorAssignableVariation•Maybeduetoa)improperlyadjustedmachineb)operatorerrorc)defectiverawmaterial•Aprocessoperatinginthepresenceofassignablecausesofvariationissaidtobe“out-of-control”ProcessCapabilityProcessCapabilityistheinherentreproducibilityofaprocess’soutput.Itmeasureshowwelltheprocessiscurrentlybehavingwithrespecttotheoutputspecifications.Itreferstotheuniformityoftheprocess.Capabilityisoftenthoughtofintermsoftheproportionofoutputthatwillbewithinproductspecificationtolerances.Thefrequencyofdefectivesproducedmaybemeasuredina)percentage(%)b)partspermillion(ppm)c)partsperbillion(ppb)ProcessCapabilityProcessCapabilitystudiescan•indicatetheconsistencyoftheprocessoutput•indicatethedegreetowhichtheoutputmeetsspecifications•beusedforcomparisonwithanotherprocessorcompetitorProcessCapabilityvsSpecificationLimitsa)b)c)a)Processishighlycapableb)Processismarginallycapablec)ProcessisnotcapableThreeTypesofLimitsSpecificationLimits(LSLandUSL)•createdbydesignengineeringinresponsetocustomerrequirementstospecifythetoleranceforaproduct’scharacteristicProcessLimits(LPLandUPL)•measuresthevariationofaprocess•thenatural6limitsofthemeasuredcharacteristicControlLimits(LCLandUCL)•measuresthevariationofasamplestatistic(mean,variance,proportion,etc)ThreeTypesofLimitsDistributionofIndividualValuesDistributionofSampleAveragesProcessCapabilityIndicesTwomeasuresofprocesscapability•ProcessPotential–Cp•ProcessPerformance–Cpu–Cpl–CpkProcessPotentialTheCpindexassesseswhetherthenaturaltolerance(6)ofaprocessiswithinthespecificationlimits.6LSLUSLToleranceNaturalTolerancegEngineerinCpProcessPotentialACpof1.0indicatesthataprocessisjudgedtobe“capable”,i.e.iftheprocessiscenteredwithinitsengineeringtolerance,0.27%ofpartsproducedwillbebeyondspecificationlimits.CpRejectRate1.000.270%1.330.007%1.506.8ppm2.002.0ppbProcessPotentiala)b)c)a)Processishighlycapable(Cp2)b)Processiscapable(Cp=1to2)c)Processisnotcapable(Cp1)ProcessPotentialTheCpindexcomparestheallowablespread(USL-LSL)againsttheprocessspread(6).Itfailstotakeintoaccountiftheprocessisnotcenteredbetweenthespecificationlimits.ProcessiscenteredProcessisnotcenteredProcessPerformanceTheCpkindexrelatesthescaleddistancebetweentheprocessmeanandthenearestspecificationlimit.3USLCpu3LSLCpl3NSLC,CMinimumCplpupkProcessPerformanceCpkRejectRate1.00.13–0.27%1.10.05–0.10%1.20.02–0.03%1.348.1–96.2ppm1.413.4–26.7ppm1.53.4–6.8ppm1.6794–1589ppb1.7170–340ppb1.833–67ppb1.96–12ppb2.01–2ppbProcessPerformancea)Processishighlycapable(Cpk1.5)b)Processiscapable(Cpk=1to1.5)c)Processisnotcapable(Cpk1)a)Cp=2Cpk=2b)Cp=2Cpk=1c)Cp=2Cpk1Example1SpecificationLimits:4to16gMachineMeanStdDev(a)104(b)102(c)72(d)131DeterminethecorrespondingCpandCpkforeachmachine.Example1A5.0464166LSLUSLCp5.043410;431016Min3LSL;3USLMinCpkExample1B0.1264166LSLUSLCp0.123410;231016Min3LSL;3USLMinCpkExample1C0.1264166LSLUSLCp5.02347;23716Min3LSL;3USLMinCpkExample1D0.2164166LSLUSLCp0.113413;131316Min3LSL;3USLMinCpkProcessCapabilityForanormallydistributedcharacteristic,thedefectiverateF(x)maybeestimatedviathefollowing:Forcharacteristicswithonlyonespecificationlimit:a)LSLonlyb)USLonlyUSLxPrLSLxPrxFUSL1LSLUSLLSLZ1ZLSLUSLLSLZLSLxPrxFUSLZ1USLxPrxFExample2SpecificationLimits:4to16gMachineMeanStdDev(a)104(b)102(c)72(d)131Determinethedefectiverateforeachmachine.Example2MeanStdDevZLSLZUSLF(xLSL)F(xUSL)F(x)104-1.51.566,80766,807133,614102-3.03.01,3501,3502,70072-1.54.566,807366,811131-9.03.001,3501,350LowerSpecLimit=4gUpperSpecLimit=16gProcessPotentialvsProcessPerformance(a)PoorProcessPotential(b)PoorProcessPerformanceLSLUSLLSLUSLExperimentalDesign•toreducevariationExperimentalDesign•tocentermean•toreducevariationProcessPotentialvsProcessPerformanceProcessPotentialIndex(Cp)Cpk1.01.21.41.61.82.01.02,699.91,363.31,350.01,350.01,350.01,350.01.2318.3159.9159.1159.1159.11.426.713.413.413.41.61.60.80.81.80.10.02.00.0DefectiveRate(measuredindppm)isdepe