质量控制与质量管理（清华大学）aql system

基于AQL的接收抽样体系清华大学工业工程系吴甦AQLSystemAQLsystem:Acceptablequalitylevel

MIL-STD-105,ANSI/ASQC,orABCstandardDefinitionofAQLInordertoestablishacceptancecriteriaforanyparticularqualitycharacteristicofaproduct,itisfirstnecessarytoprescribeamaximumpercentdefectivethat,foracceptancesamplingpurposesonly,isconsideredacceptableasaprocessaverage.ThisacceptablequalitylevelusuallyhasbeenabbreviatedAQL.OtherdefinitionsofAQLJan-STD-105:Percentageofdefectiveitemsinaninspectionlotsuchthatthesamplingplanwillresultintheacceptanceof95%ofthesubmittedinspectionlotscontainingthatpercentageofdefectiveitemsMil-STD-105:theacceptablequalitylevelisanormalvalueexpressedintermsofpercentdefectiveordefectsperhundredunits,whicheverisapplicable,specifiedforagivengroupofdefectsofaproductAQLforacceptancesampling在实际的生产和交付过程中，并不存在一个可接收的质量水平这一说，AQL只是为了接收抽样的目的而人为定出的。因此，AQL的存在并不意谓着可以提供有缺陷的产品。AQL的提出：如何确定可接受的标准生产方消费方为什么抽样检验比全数检验会对提升质量产生更大的动力qualitycostsscrapreworkdeviationof

outputquantitiesdepreciationscreening

inspection抽样不合格全检repeated

inspectionproblem

investigationothercostsscrapreworkwarrantyproducer-

liabilityothercosts?lossofimage?lossofmarketinternalexternalfailurecostsqualityplanningqualitycapability

investigationsinspectionplanqualityauditmanagementof

qualitydepartmenttraininginqualityassurancequality-promotion-programmesquality-comparisonwith

competitorsothermeasuresof

failurepreventionfailurepreventioncostsstockreceiptinspectionmanufacturinginspectionfinalinspectionacceptance-inspectioninspectionequipmentmaintenanceofinspection

equipmentqualityreportslaboratorytestinspectiondocumentsothermeasuresand

procurementsforquality

inspectioninspectioncosts检验成本Qualitycostsareinterpretedasimpacttomanufacturingcosts.Misleadingconnectionbetweencostsandquality.Thecostsarenotcausedbyquality,butratherbythefailurenottocomplywithquality.Qualitycostsinthetraditionalviewdistractfromactualsavingpotentials.failureprevention

andinspectioncostscostsfailurecostsqualitylevelatoptimalcoststotal

qualitycostswell0%100%50%95%principallyplannednonavoidablewellknowninthesumoverheadcostsconformity-costscostsfortheaccordanceof

productfeaturesandcustomer

requirementsprincipallynotplannedavoidableseparatelysizablesinglecostsnon-conformity-costscostsforthedeviationofproduct

featuresfromcustomerrequirements

establishedclassificationofquality-basedcosts:remaining

costspreventiveproceduresinspectioncostsfailurepreventioncostscorrectiveprocedurescostsoflostsalesinternal,externalfailurecostsquality-basedcostclassificationaccordingtoDINISO8402(outofdate)non-conformity-

costsqualitylevelqualitycostsconformity-costs0%100%50%95%costsoflost

salesandnon-

conformity-coststotalqualitybasedcostsincludingcostsoflost

salesBpointB:effectiveoptimalqualitylevelEpointA:optimalqualitylevelwithoutcostsoflostsalesCAtotalqualitybasedcostswithoutcostsoflostsalesDPDCPDC:

potential

todecrease

costsProcessAverage12.6.3AQL体系要求对最近的过程平均进行估计，通常从过去的10个批次中进行，来决定是正常检验，加严或放松。了解过程平均是好于还是差于AQL，质量是在改善还是恶化。过程平均＝发现的不合格品数/检验总数通常单词抽样时已能决定拒收时也应检查完两次以上用第一次结果来估计过程平均拒收批也应检查完相应的p控制图N=1000,AQL=1.5%N=1000J+AQL=1.5%n=80,c=3两次抽样表O第一次抽样（50，1，4）第二次（50，4，5）多次表R（20，+,3)(20,0,3)…SamplesizecodeSinglesamplingplanAQL值P12.4表头上的AQL值既可以是不合格品百分比，也可以是每百件产品缺陷总数AQL在10以上者，都视作每百件产品的缺陷总数。12.5.3当AQL值低于0.01%时，不建议使用此类标准下的抽样检验（TableL）。ProbabilitiesofacceptanceoflotshavingAQLpercentdefectiveInallAQLsystems,theacceptancecriteriaundernormalinspectionhavechosentoprotecttheproduceragainstrejectionoflotsmeetingthequalitystandard.thesmallerthesamplesize,thegreatertheproducer’srisk.theconsumer’sriskofacceptingalotmuchworsethantheAQLisalsomuchgreaterwithasmallsamplesize.Whyandwhentightenedorreducedsampling?Economically(reduced)don’tknowthequalityhistory(tightened)toprotectthecustomeragainstacceptinglotswhosequalityisworsethanAQLProcedureforNormalinspectiontightenedinspectionandreducedinspectiontightenedsamplingNormaltightened%%87.881.89180.996.386.998.793.9Reducedsamplingthedifferencebetweenacceptrejectcriteriaisnot1.whatisthedecisionwhendefectivenumberiswithintherange.ConditionsforreducedIt’snoteasytobesampling-freeifsomeone’squalityisnotreallygood.Page476对孤立批次的接收抽样方案选择孤立批次，应从保护消费者的利益出发；ABC标准规定，对于孤立批，基于AQL和LimitingQuality（LQ）进行抽样方案选择；此处LQ与LTPD的含义相同；因此相当于从OC曲线上决定了两点。SelectinganacceptanceplanforanisolatedlotP493，12.12AQL体系：从保护生产方的利益出发LQ体系：从保护消费方的利益出发表12.1β＝0.1，AQL—可接受的LQ值（表中数值）—字母代码－抽样方案抽样方案比较逐批接收抽样，AQL＝1.0％,N=1000从TableKandTableL,CodeLetter为J，样本容量为80，抽样准则为（2，3）孤立批次抽样，AQL＝1.0％，可见相应的LQ＝6.5％，如果要求LQ减小，则抽样的样本容量增加。比较ABC－STD－105和GB/T13262－91GB/T13262-91其它抽样方法：Cameron方法P521表13.5np0.95，Pa=0.95,α=0.05，P0＝0.65％β＝0.1,先没有规定P1值现确定接收准则c值，c=3n=np0.95/p0.95=1.336/0.0065=210P0.1=np0.1/n=6.681/210=0.032=3.2%用AQL和LQ方法验证AQL＝0.65％，从表12.1，查到LQ＝3.3％的栏，见到L，样本容量＝200，查表L，抽样方案为（3，4）生产方风险：α=0.05，P0＝0.65％消费方风险：β＝0.1，P1＝1.0％n=5600表12.1已经无法找到合适的抽样方案很多情况下，要两个点都满足是不现实的。P523Dodge-Romig方法13.2.1节：Dodge－Romig表表13.1：表中方案都有相同的LTPD，但是AOQL不同13.2.3节：表13.3：所有的方案都有相同的AOQL，但LTPD不同。Dodge－Romig方法表13.1：表中方案的LTPD相同，都为5％，但AO