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1、ToleranceManagement(ToleranceManagement(公公差管理差管理) )ContentsToleranceSynthesisToleranceAllocationTotalToleranceManagementToleranceManagement31July,2002AgilentRestrictedToleranceSynthesisSynthesisorallocation?ToleranceanalysismethodWC(WorstCase)RSS(RootSumSquares)MonteCarlo(Simulationmethod)Worstcasem
2、ethodorstatisticalmethod?How?When?ToleranceManagement31July,2002AgilentRestrictedSynthesisVs.AllocationToleranceManagement31July,2002AgilentRestrictedAnalysismethodWorstCaseRSS(RootSumSquares)ToleranceManagement31July,2002AgilentRestrictedSensitivityanalysisWhatisSensitivity?ToleranceManagement31Jul
3、y,2002AgilentRestrictedSensitivityExampleDifferentvariationhavedifferentinfluencetofinalassembly.DuringdesignphaseweneedtooptimizesensitivitiesofcomponentstomaketheproductmorerobustToleranceManagement31July,2002AgilentRestrictedWorstCaseVs.StatisticalToleranceCasestudy4blocksassemblyBlocklength=10.0
4、3Assemblyrequirement:40.1(3.94.1)?ToleranceManagement31July,2002AgilentRestrictedWorst-CaseTolerance=4*0.03=0.012Blocklength=40.012(3.884.12)Result:Outofrequirement!ToleranceManagement31July,2002AgilentRestrictedStatisticalCaseStatisticalToleranceTolerance3.944.06ToleranceManagement31July,2002Agilen
5、tRestrictedExtremeCaseWhenblockisin0.976 0.06,usingstatisticaltolerancecouldcause:Blocklength:3.9040.12,OutoftoleranceToleranceManagement31July,2002AgilentRestrictedApplicationStatisticalToleranceonlycanbeusedwhentolerancedistributioniscenteredWC:Safe,criticalapplication,expensiveRSSStatistical:Inex
6、pensive,butshouldmeetassumption(centereddistribution),needgoodsuppliermanagement(Suppliershouldfollowstatisticaltolerancing)ToleranceManagement31July,2002AgilentRestrictedToleranceAllocationPopularMethodEqualToleranceEqualtolerancesareassignedtoallcomponents(Badpractice)EqualprecisionAllpartsinanass
7、emblyhavethesameprecision(manufacturingdifficulty)WeightedprecisionAllpartsaresetthesameprecisioninitially,usedifferentweighttooptimizetoleranceallocationToleranceManagement31July,2002AgilentRestrictedProportionalScalingProcedure:1.Assigningreasonabletolerancebasedonprocessordesignguidelines2.Alltol
8、erancesaresummedtoseeiftheymeetthespecifiedtolerance.3.Ifnot,alltolerancearescaledbyaconstantproportionalityfactor.ToleranceManagement31July,2002AgilentRestrictedIllustrationofProportionalScalingToleranceManagement31July,2002AgilentRestrictedPracticalProblemDimValueToleranceDesignFixedARetainingRing
9、0.05050.0015B8.000?Cbearing0.50930.0025D0.400?E7.711?F0.400?Gbearing0.50930.0025Required clearance:0.020 0.015ToleranceManagement31July,2002AgilentRestrictedDimValueToleranceDesignFixedARetainingRing0.05050.0015B8.0000.008Cbearing0.50930.0025D0.4000.002E7.7110.006F0.4000.002Gbearing0.50930.0025Initi
10、alSettingToleranceManagement31July,2002AgilentRestrictedProportionalScalingWorst-CaseTSUM=+TA+TB+TC+TD+TE+TF+TG=+.0015+.008+.0025+.002+.006+.002+.0025=.0245(toolarge)ProportionalTASM=.015=.0015+.0025+.0025+P*(.008+.002+.006+.002)P=.47222TB=.47222(.008)=.00378TE=.47222(.006)=.00283TD=.47222(.002)=.00
11、094TF=.47222(.002)=.00094DimValueToleranceDesignFixedARetainingRing0.05050.0015B8.0000.00378Cbearing0.50930.0025D0.4000.00094E7.7110.00283F0.4000.00094Gbearing0.50930.0025ToleranceManagement31July,2002AgilentRestrictedStatisticalAllocationDimValueToleranceDesignFixedARetainingRing0.05050.0015B8.0000
12、.012Cbearing0.50930.0025D0.4000.0028E7.7110.084F0.4000.028Gbearing0.50930.0025Statistical methodToleranceManagement31July,2002AgilentRestrictedAllocationbyWeightFactorsBased on machining difficulty,different weight can be assign to a tolerance of a part to optimizeFor example, B,D, E, F are assigned
13、 10,20,10,20 as weight.ToleranceManagement31July,2002AgilentRestrictedWorstCaseDimValueToleranceDesignFixedARetainingRing0.05050.0015B8.0000.00309Cbearing0.50930.0025D0.4000.00155E7.7110.00232F0.4000.00155Gbearing0.50930.0025ToleranceManagement31July,2002AgilentRestrictedStatisticalDimValueTolerance
14、DesignFixedARetainingRing0.05050.0015B8.0000.01010Cbearing0.50930.0025D0.4000.00505E7.7110.00757F0.4000.00505Gbearing0.50930.0025ToleranceManagement31July,2002AgilentRestrictedComparisonToleranceManagement31July,2002AgilentRestrictedToleranceforcouplingDimensionaltoleranceGeometricaltoleranceSynthes
15、isofdimensionaltoleranceandgeometricaltoleranceWhenfeatureofsizehasbeenassigndimensionaltoleranceandgeometricaltolerance,thetotaltoleranceofmatingisdifferentfromconventionalmatingtolerance.ToleranceManagement31July,2002AgilentRestrictedExample-linkagemechanismToleranceManagement31July,2002AgilentRes
16、trictedCalculationMinimalGap=VChole-VCshaft=30-30=0.0MaximumGap=LMSholeLMSShaft=30.5-29.5=1.0Maximumdisplacement=RCholeLMSshaft=31.0-29.5=1.5ToleranceManagement31July,2002AgilentRestrictedValidationinsub-assembly2mode:VC(virtualcondition)modeandRC(resultantcondition)Forcriticaldimensionchain,allcoup
17、lingshouldbevalidatedatvirtualconditionandresultantcondition(Twoextremecondition)ThisprocesscanexposedesignerrorinembodimentdesignToleranceManagement31July,2002AgilentRestrictedCommon problems in tolerance managementConception: Feasibility analysis Lack of general knowledge and understanding Difficu
18、lt to represent GD&T tolerances in tolerance chain calculationsDetailDesign: Difficult to make a cost efficient tolerance allocation Difficult to represent GD&T tolerances in tolerance chain calculations The tolerance standard is erroneously applied, resulting in inconsistent requirementsManufacturi
19、ng: The tolerance standard is erroneously applied, resulting in inconsistent requirementsDrawings are misinterpreted which gives errors in manufacturing and verificationInspection: The measurements are erroneously performed Inconsistent use of datumConceptionDesignDetail DesignManufacturing Dev.Insp
20、ectionTotalToleranceManagementToleranceManagement31July,2002AgilentRestrictedWarrantyFailureorIn-housefailure?A product passing final test doesnt mean it is of high quality,especially those products pass final test just at the end of tolerance zone.it will short the product life, increase warranty c
21、ost.1.DesignTolerances are assigned to each component at a balanced justification.2.ManufacturingProcess Capability is maintained,manufacturing equipments dont “eat” too much tolerance,Reduce possibility of process failureHowtoevaluateagoodtolerancemanagementToleranceManagement31July,2002AgilentRest
22、rictedSomeStatisticstermsMeanStandarddeviationToleranceManagement31July,2002AgilentRestrictedProcessCapabilityCpCpkToleranceManagement31July,2002AgilentRestrictedExplanationCp1.0Processistoobad1.0Cp1.33Good1.33Cp=2.0andCpk=1.5imply6SIGMAquality(3.4ppmdefective,)ToleranceManagement31July,2002AgilentR
23、estrictedBestPracticeMotorola6SigmaTaguchisMethodConceptionDesignParameterDesignToleranceDesignToleranceManagement31July,2002AgilentRestrictedVariationscausingcomponentfailure5M1EMan,Method,Machine&MeasuringTool,Material,EnvironmentVariationsindifferentproductphasePhaseDesignComponentAssemblyVariati
24、onDesignisnotrobust,toosensibletovariationMachineprecisionProcessvariationManufacturingprocessFixtureprecisionAssemblyprocessCalibrationtoolprecisionProcessvariationResultToleranceistootight,highmanufacturingcost.Highdefectonarrival,scraprateistoohighDOA,HighFailureRate,ShortenproductlifeToleranceMa
25、nagement31July,2002AgilentRestrictedDesignManufacturingInspectionVendor ManagementFixture DevelopmentAssembly Process DevelopmentCalibration Process DevelopmentToleranceManagementActivitiesinDifferentPhaseToleranceManagement31July,2002AgilentRestrictedDesignPhaseRobustdesignSensitivityanalysisandopt
26、imizationManufacturingmethod?BalancebetweenassemblytoleranceandcomponenttoleranceBuildhighprecisionormanufacturinghighprecision?Fixtureandcompliantassemblycanensuretighttolerance.Example:InjectorBackplateAssemblytoleranceorcalibratedtolerance?Ifaproducthashighrepeatability,productcanbecalibratedtoho
27、mepoint,avoidinghighmanufacturingcost.Example:TrayandinjectorToleranceManagement31July,2002AgilentRestrictedToleranceManagement31July,2002AgilentRestrictedManufacturingFixturedesignUsecorrectpositioningmethod,TrynottowidentolerancezoneorreducetolerancezoneAssemblyprocessReduceoperatorinfluenceinproc
28、essvariationAddtestprocessforeachsub-assemblyPreventiveMaintenancePreventequipmentfrommalfunctionBepreparedratherthanfire-fighterToleranceManagement31July,2002AgilentRestrictedSamplingCommonProblem:Whenproblemoccurs,weknowtherearesomethingwrongSamplingEverythingcangowrong,beproactive!Samplemethod?Ha
29、vevendortosamplepartsandsubmitasamplingreporttoconsumer.100%incominginspectionisnotencouragedConsumerdevelopsasamplingplan:N,n,A,RN-lotsizen-samplesize,A-acceptsize,RRejectsize.ToleranceManagement31July,2002AgilentRestrictedSamplingSampleperiodCriticalpartNon-CriticalPartRejectmethodThebestwayistorejectallpartstovendoratvendorsexpenseAdvantages:PushvendorsimprovequalityVendorunderstandwhatiswrongReduceimpacttoproductionlineDisadvantages:Impacton-time-deliveryToleranceManagement31July,2002AgilentRestricted结束结束
