© ABSL Power Solutions 2007 © STM Quality Limited STM Quality Limited Measurement Systems Analysis TOTAL QUALITY MANAGEMENT M.S.A.

© STM Quality Limited STM Quality Limited Outline and Objectives Introduce Measurement Systems Assess Measurement Systems Performance Understand Measurement System Variation

© STM Quality Limited STM Quality Limited Requirements for M.S.A. TS16949 Clause states: Statistical studies shall be conducted to analyse the variation present in the results of each type of measuring and test equipment system. This requirement shall apply to measurement systems referenced in the control plan. The analytical methods and acceptance criteria used shall conform to those in customer reference manuals on measurement systems analysis. Other analytical methods and acceptance criteria may be used if approved by the customer.

© STM Quality Limited STM Quality Limited Process Control People Methods Material Equipment Environment A Typical Process Input PROCESS Process / System Product Output Identifying Improvement Opportunities Accurate Measurement using Measurement System Analysis

© STM Quality Limited STM Quality Limited New Process Acceptance Observed Process Variation Actual Process Variation Production Gauge Variation

© STM Quality Limited STM Quality Limited Assessing Measurement Systems Location variation – Bias – Stability Width variation – Linearity – Repeatability, Reproducibility

© STM Quality Limited STM Quality Limited Determining and Assessing Bias Bias is the difference between the observed average of measurement and the reference value. The reference value, also known as the accepted reference value or master value, is a value that serves as an agreed-upon reference for the measured values. A reference value can be determined by averaging several measurements with a higher level of measuring equipment. Reference Value Observed Average Value Bias

© STM Quality Limited STM Quality Limited Determining and Assessing Stability Stability (or drift) is the total variation in the measurements obtained with a measurement system on the same master or part when measuring a single characteristic over an extended time period Reference Value Time

© STM Quality Limited STM Quality Limited Determining and Assessing Linearity Linearity is the difference in the bias values through the expected operating range of the gauge. Reference Value 50mm Observed Average Value Smaller Bias 200mm Reference Value Observed Average Value Larger Bias

© STM Quality Limited STM Quality Limited Determining Repeatability Repeatability is the variation in measurements obtained By one appraiser with one measurement instrument when used several times while measuring the identical characteristic on the same part Repeatability

© STM Quality Limited STM Quality Limited Determining Reproducibility Reproducibility is the variation in the average of the measurements made by different appraisers using the same measuring instrument when measuring the identical characteristic on the same part Reproducibility

© STM Quality Limited STM Quality Limited Preparing For A Measurement System Study Variable Gauge Study (Average and Range Method) The average and range method of gauge study breaks the gauge error into repeatability and reproducibility. Optimum conditions: 3 operators; 3 trials; 10 parts. Study of the results can provide information concerning the causes of the measurement error. If reproducibility is large compared to repeatability then; The operator is not properly trained in how to use and read the gauge; Graduations on the gauge are not clear.

© STM Quality Limited STM Quality Limited Determining and Assessing Repeatability and Reproducibility There are three methods: Range Method; Average and Range Method; Analysis of Variation Method (ANOVA).

© STM Quality Limited STM Quality Limited Determining and Assessing Repeatability and Reproducibility Range Method Gives a quick approximation of measurement variability. It does not decompose the variability into repeatability and reproducability. Conducted with 2 appraisers and 5 parts; Each appraiser measures each part once; Evaluate the range at each part; Estimate the variation between the measurement results over the average Range (R/d2); Gauge R&R = 99%-area under the normal distribution curve (2*2,576*variation). (not sufficient for PPAP and QS-9000 clause )

© STM Quality Limited STM Quality Limited Determining and Assessing Repeatability and Reproducibility Average and Range Method Evaluates Repeatability and Reproducibility separately; Conducted typically with three appraisers and 10 parts; Each appraiser measures each part three time in a random order; Evaluation graphical or numerical; EV (equipment variation) (99%- norm. distr.) AV (appraiser variation) (99%- norm. distr.) R&R (R&R)² = EV² + AV²(99%- norm. distr.) Part Variation PV(99%- norm. distr.) Total VariationTV² = (R&R)² + PV²(99%- norm. distr.)

© STM Quality Limited STM Quality Limited Determining and Assessing Repeatability and Reproducibility Analysis of Variation Method Evaluates Repeatability and Reproducibility separately; Evaluates Interaction between appraiser and part; Conducted typically with three appraisers and 10 parts; Each appraiser measures each part three time in a random order; Evaluation graphical or numerical; EV (equipment variation) (99%- norm. distr.) AV (appraiser variation) (99%- norm. distr.) R&R (repeatability, reproducibility and interaction (I) R&R (R&R)² = EV² + AV²+I²(99%- norm. distr.) Part Variation PV(99%- norm. distr.) Total Variation TV² = (R&R)² + PV²(99%- norm. distr.)

© STM Quality Limited STM Quality Limited Determining and Assessing Repeatability and Reproducibility If repeatability is large compared to reproducibility, the reasons may be: The instrument needs maintenance; The gauge should be redesigned to be more rigid; The clamping or location for gauging needs to be improved; There is excessive part variation. If reproducibility is large compared to repeatability, then possible causes could be: The appraiser needs to be better trained in how to use and read the gauge instrument; Calibrations on the gauge dial are not clear; A fixture of some sort may be needed to help the appraiser use the gauge more consistently.