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SPC for Test System Gauge R&R2有多少個黑點？3這些橫線是不是平行的？4是靜的還是動的？5三個正方形6幾何謎題7沒有適當的量測工具沒有適當的量測工具就無法管理品質就無法管理品質!8 比較式 絕對式待測量轉換訊息標準值顯示量測儀量測之種類量測之種類待測量標準量轉換訊息轉換訊息比測儀顯示轉換放大9Basic ConceptsEvery Process produce a“Product”.Every product possesses Qualities(Features)Every Quality Feature Can be measuredTotal Variation=Product Variation+Measurement VariationSome Variation Inherent in System Design.Some Variation is due to a Faulty performance of the System(s).10Components of Measurement SystemEquipment or GageType of Gage:Attribute:go-no go,vision systems Variable:calipers,probe,coordinate measurement machinesUnit of Measurement-discriminationAt least 1/10 of 6*process standard deviation(6 6s)Other rules:at least 1/10 of toleranceOperator&Operating InstructionsPart locating or orientation schemea gage must be able to consistently locate the part being measured.11Terms You Should Know Measurement system:The collection of operations,procedures,gages and personnel use to obtain measurements of work piece characteristics Gage:A device used to obtain measurements Repeatability:Repeatability(Precision)The variation in measurement obtained with one measurement instrument when used by one operator to measure.)an identical characteristic on the same part.(EV:Equipment Variation Reproducibility:The variation in the average of the measurements made by different operators using the same measurement instrument when measuring identical characteristics on the same part.(AV:Appraiser Variation)12Terms You Should KnowBias:The difference between the observed average of measurements and the reference value.Percent R&R:The percentage of process variation related to the measurement system for repeatability and reproducibility Stability:The total variation in the measurements obtained with a measurement system on the same master or parts when measuring single characteristics over an extended timeperiod.Linearity:The difference in the bias values through the expected operating range of the gage.131.AccuracyDifference between the true average and the observed average(true average may be obtained using a more precise measuring tool)142.ReproducibilityVariation in average of measurements made by different operators using the same gage measuring the same part.Appraiser Variation(AV)153.Repeatability(Precision)Random variation in measurements when one operator uses the same gage to measure the same part several times.Equipment Variation(EV)164.StabilityDifference in the average of at least 2 sets of measurements obtained with a gage as a result of time.17Precision and Accuracy18Accuracy and StabilityMeasure same parts using a more precise instrument(Accuracy).Measure same parts using the same gage at a later date(Stability or Drift).19Measurement System Variables20Possible Sources of ProcessVariation21Sources of Measurement Error Systematic Variations 1.accuracy:improper calibration of equipment 2.reproducibility:different operators using same equipment with different techniques Random Variations 3.repeatability:(for example,inconsistent part locating)Periodic Variations 4.stability:wear,deterioration,environmental conditions22The GR&R Design ModelSuppose multiple operators,measure multiple parts several times each.Then:In terms of the gage performance,between-operator reproducibility is due to the operator effect and the operator*part interaction.Within-operator repeatability is from the pure error term.23The Components of Variance24Measurement Error Gage R&R25AveragesANOVA analysis begins with the calculation of all relevant averages.Heres an example:26Types of Gage Error and AnalysisMethods:Accuracy Gage Accuracy(Bias)Study Gage Linearity Study.Repeatability&Reproducibility Gage R&R(Methods:X-bar/Range or ANOVA)Repeated Measurement StudyRepeatability Static&Dynamic StudyStability Repeated Measurements27Variance PartitioningThe total variance of the GR&R data is partitioned into components according to the model.Variances add,so all partitioned pieces sum to the total data variance!28Two Way Anova Table29Gage R&R AcceptanceTo determine acceptability,a ratio is typically formed comparing gage variation to either:Gage R&R%of Tolerance Width Gage R&R%of Total Variation 6s 6s-represents 99.73%of values if normal distribution 5.15 s s-represents 99%of values if normal distribution30Criteria for Evaluating Gage R&R Gage R&R%-TV or R&R%-Tolerance if R&R%is:30%=measurement system needs improvement31Conducting a Gage R&R Study1.Plan the approach What is nature of operator and measurement interaction?Reproducibility can be negligible sometimes.2.Select 3 well trained operators3.Select 10 parts for test,Select sample parts should represent entire normal production range.(Prefer cover the distribution of+/-4 sigma)4.Repeat measure each parts 3 times.5.Take measurements in random order.6.Take blind measurement Person measuring doesnt know which piece is being measured,what previous measurements were,or what other appraisers found.32Conducting a Gage R&R Study7.Record all measurements on worksheet.8.Calculate trial range for each piece for each operator and record values,calculate R&R(square root of the sum of the squares of the repeatability and reproducibility).9.Keep the standard parts&its reading for“Equipment Correlation“purpose33Guidelines For Gauge R&R AcceptanceUnder 10%Error:Acceptable10%30%Error:May be Acceptable depending on the importance of the application.Over 30%error:Improvement is needed34Gauge R&R Study35Gauge R&R Study36Gauge R&R Study37Gauge R&R Study38Gauge R&R Study39Anova Method ExampleEquipment Calibration By Simple Linearity Model(Y=mX+b )41Selection of Standard UnitsSet up about 10 pcs standard units which can cover the overall spread of normal production.Prefer 2 reject unit beyond upper/lower spec.Aging all units Find standard reading42Regression Analysis:Equipment vs StandardMeasure Standard unit on each individual test equipment several times.Take the average of measurement data for each unitRegression Analysis;Equipment Reading vs Standard Reading.If correlation coefficient 90%,then calculate the slope and off-set per test m/c.If correlation coefficient chance and off diagonal frequencies should be chance.Use marginal frequencies/probabilities to estimate chance agreement.Proportion agreement observed,po=ipii=1/n iniiProportion agreement expected by chance,pc=ipi.x p.i po-pc 1-p cKappa,K=po=.53+.14.03=.7pc=.39+.075+.01=.475 .7-.475 K=1-.475=.429 K=1,perfect agreementK=0,chance agreementK0.75.If Kappa is 0.75,the measurement system must be improved before accepting or rejecting parts.Computing Kappa(GR&R Test For visual inspector)51Example of Computing Kappa52Example of Computing KappaProportion agreement observedProportion agreement expected by chanceK=P(agreement|no agreement by chance)1-pc=1-0.503=0.497 of cases where no agreement by chancepo-pc=0.825 0.503=0.322 of cases are those non-chance agreement cases where observers agreed.&
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