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Measurement Systems Analysis. Introduce Measurement Systems Assess Measurement Systems Performance Understand Measurement System Variation. www.qualimations.com. Measurement Systems Analysis. Process Control. A Typical Process. People Methods Material Equipment Environment. PROCESS.

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  1. Measurement Systems Analysis • Introduce Measurement Systems • Assess Measurement Systems Performance • Understand Measurement System Variation www.qualimations.com Measurement Systems Analysis

  2. Process Control A Typical Process People Methods Material Equipment Environment PROCESS Product Identifying Improvement Opportunities Input Process / System Output Accurate Measurement using Measurement System Analysis www.qualimations.com Measurement Systems Analysis

  3. Assessing Measurement Systems How good is our measurement system? 2T = 2p + 2m • Observed Process Variation • Production Gauge Variation • Actual Process Variation www.qualimations.com Measurement Systems Analysis

  4. Assessing Measurement Systems • Location variation • Bias • Stability • Width variation • Linearity • Repeatability, Reproducibility www.qualimations.com Measurement Systems Analysis

  5. Determining and Assessing Bias • Biasis the difference between the observed average of measurement and thereference 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. Observed Average Value Bias Reference Value www.qualimations.com Measurement Systems Analysis

  6. Determining and Assessing Stability Time • 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 www.qualimations.com Measurement Systems Analysis

  7. Determining and Assessing Linearity • Linearityis the difference in the bias values through the expectedoperating rangeof the gauge. Reference Value Reference Value Observed Average Value Observed Average Value Smaller Bias Larger Bias 50mm 200mm www.qualimations.com Measurement Systems Analysis

  8. Determining Repeatability • Repeatabilityis the variation in measurements obtained • Byone appraiser • with one measurement instrument • when used several times • while measuring the identical characteristic • on thesame part Repeatability www.qualimations.com Measurement Systems Analysis

  9. Determining Reproducibility • Reproducibilityis the variation in the average of the measurements made • bydifferent appraisers • using the same measuring instrument • when measuring the identical characteristic • on thesame part Reproducibility www.qualimations.com Measurement Systems Analysis

  10. 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. www.qualimations.com Measurement Systems Analysis

  11. Determining and Assessing Repeatability and Reproducibility • If repeatabilityis 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 reproducibilityis 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. www.qualimations.com Measurement Systems Analysis

  12. Acceptability Criteria • R&R Indices •  10% Acceptable Measurement System • 10% - 30% May be acceptable based upon application, cost of measurement device, cost of repair, •  30%Not acceptable. Measurement system needs improvement. • Number of Distinct Categories Index • 1 Unacceptable. One part cannot be distinguished form another. • 2 -4 Generally unacceptable •  5 Recommended www.qualimations.com Measurement Systems Analysis

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