1_3Cm_CmK,-Cp_CpK意义

Cm/CmK和Cp/CpK意义Statistics—Cm/CmK,Cp/CpK目的Objective2通过介绍，了解拧紧精度的统计学概念Thispresentationwillintroduceyoutothebasicsoftighteningstatistics如何来保证精度Howcanyouguarantytobeontolerances?3•通过测试工具至少25次，来计算能力指数Thetoolhastobetestedontheapplication.Doatleast25tightening.Makestatisticalcalculation.•通过测试数据的计算来保证YourguaranteeisbasedonthecalculationofthecapabilityTESTINGistheonlywaytoguarantee工具拧紧一次是+-10%如何保证拧紧1万、10万次甚至100万次，工具的精度也在+-10%之内？Cp/Cpk–Cm/Cmk的概念Cp/Cpk–Cm/Cmkconception•Cm/Cmk:Capabilitymachine设备能力指数所有的测试应以实验室设备为基础•Cp/Cpk:Capabilityprocess过程能力指数所有的测试在实际的装配线完成4有什么不同？5平均值Meanvalue=averagevalue180+165+…+1957=180cmXn=180cm标准偏差—代表了分布的离散度Standarddeviationindicatesthescatter(120-165)2+(125-165)2+…=107-1=s-()²x(n-1)7个人的平均身高Samemean,differentstandarddeviation.Samestandarddeviation,differentmeans.FrequencyXFrequencyXSamemean,differentstandarddeviation.Samestandarddeviation,differentmeans.FrequencyXFrequencyXFrequencyXFrequencyXCp/CpK的计算Cp/Cpkcalculation6Cp/CpK的计算USL-LSL6sCp=Cpk=Min(,)µ-LSL3sUSL-µ3s≤考虑两个边界和离散度，同时考虑中心只考虑两个边界和离散度练习Exercice7FrequencyTorque(LO)=45(HI)=55Mean=49客户要求的目标值50+/-5Nm.现有工具拧紧的数据，平均扭矩49Nm，σ=0.8Nm.工具满足要求吗?HI-AVE=55-493σ=2.4右侧:(HI-AVE)/3σ=(55-49)/(3*0.8)=2.5AVE-LO=49-453σ=2.4=(49-45)/(3*0.8)=1.7左侧:(AVE-LO)/3σT=50Cp=2.08Cpk=1.7Cp=(HI-LO)/6σ=(55-45)/(4.8)=2.08Thetooliscapable8这三个Cp值是一样的—因为离散度是一样的但是CpK是不一样的—因为离中心的距离是不一样的Cp/CpK的计算Cp/Cpkcalculation9Cp合格CpK不合格Cp不合格CpK不合格Cp合格CpK不合格Cp/CpK的计算Cp/Cpkcalculation10频率Frequency6s目标Target频率Frequency6s目标Target频率Frequency6s目标TargetCp/CpK的计算Cp/Cpkcalculation111-客户要求customerrequirements2-实际数据Launchdarts3-计算Calculate6s4-计算CpKCalculateCpK条件:Cpk1.33以满足ISO5393CONDITION:Cpk1.33forbeingcapable-ISO5393Cp/CpK的计算Cp/Cpkcalculation•仅仅有扭矩精度的要求是没有意义的•只有Cpk要求，没有精度要求也是没有意义的12扭矩精度torqueaccuracy•仅仅有扭矩精度的要求是没有意义的客户要求：10±1Nm13No.ResultNm110.0210.3310.349.7510610.4710.189.699.81010.5作为客户，你接受吗？扭矩精度torqueaccuracy•仅仅有扭矩精度的要求是没有意义的客户要求：10±1Nm14No.ResultNm110.0210.3310.349.7510610.4710.189.699.81010.5Max-Minstdev(Max-Min)/6stdevCp20.311.09Cpk(Hi)Max-meanstdev(Max-mean)/3stdev0.90.311.01Cpk(Low)mean-Minstdev(mean-Min)/3stdev1.10.311.17Cpk=Cp=扭矩精度torqueaccuracy15合格率%68.395.599.7399.993799.999943≒100每一百萬件之不良(Dppm)Defectspermillionparts31.74.5Cpk每一百件之不良Defectsper100parts1.331.6720.6710.330.00630.0000570.0000002317310455002700630.570.0020.27扭矩精度torqueaccuracy•只有Cpk要求，没有精度要求也是没有意义的客户要求：10±1.5Nm精度从±10%放宽到±15%，Cpk值由1.01变为1.5616No.ResultNm110.0210.3310.349.7510610.4710.189.699.81010.5Max-Minstdev(Max-Min)/6stdevCp30.311.64Cpk(Hi)Max-meanstdev(Max-mean)/3stdev1.40.311.56Cpk(Low)mean-Minstdev(mean-Min)/3stdev1.60.311.71Cpk=Cp=扭矩精度torqueaccuracy扭矩精度torqueaccuracy•仅仅有扭矩精度的要求是没有意义的•只有Cpk要求，没有精度要求也是没有意义的17两个条件相互制约！缺一不可18合格率%68.395.599.7399.993799.999943≒100每一百萬件之不良(Dppm)Defectspermillionparts31.74.5Cpk每一百件之不良Defectsper100parts1.331.6720.6710.330.00630.0000570.0000002317310455002700630.570.0020.27结论conclusion•计算重复精度时，客户必须客户必须给出以下两个信息Tocalculatestatistics,thecustomermustgivesyou2informations扭矩和公差TORQUEANDTOLERANCES•计算能力指数Theonlywaytocalculatecapabilityis测试TOMAKETESTS(最少25组25ASAMINIMUM)•两种条件来声明一把工具的精度Whatarethe2conditionstodeclareatoolcapableCP1.67ANDCPK1.33(ISO5393)•Cp值不好是工具问题IfCpisnotgooditisaproblemOFTOOL•Cp值好，而CpK值不好，那是标定问题IfCpisgoodandCpkisnotgooditisaproblemOFCALIBRATION19Cpk的计算实例exercise•某工序的拧紧要求为10±0.1Nm,实际测出50个样本本值如下﹐计算出该工序的Cpk;9.9959.9819.9639.94710.01610.0149.97110.09510.03410.0049.9289.91410.01710.02110.0069.9839.9769.96810.0269.9919.97210.05410.1599.9739.98410.01610.0039.9949.9839.9769.99210.02710.01810.00510.0039.9879.99510.00110.01710.00310.02510.0219.98710.0069.9829.9729.97510.0029.9439.994MoreThanProductivity