Gage Repeatability & Reproducibility for Continuous Data Instructor’s Name

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Transcript of Gage Repeatability & Reproducibility for Continuous Data Instructor’s Name

  • Gage Repeatability & Reproducibility forContinuous DataInstructors Name

  • IntroductionsYour NameYour Position What type of measurements you take in a given day

  • AgendaIntroduction....(30 minutes)Theory of gage R & R......(50 minutes)How to plan and execute a gage R & R study .....(20 minutes)--- Break ---How to calculate the total gage R & R for a measurement system...(75 minutes)--- Break ---How to improve a gage R & R result .....(60 minutes)--- Break ---Conclusion & Wrap-Up....(20 minutes)

  • Theory of Gage Repeatability & Reproducibility

  • What do we expect from data?AccuracyCalibration

    PrecisionRepeatability (Equipment)Reproducibility (Operator)Accurate, but not precisePrecise, but not accurate

  • Accuracy AND PrecisionA good measurement system must provide data that is BOTH accurate and precise.How do we know?By conducting a GAGE REPEATABILITY AND REPRODUCIBILITY STUDY

  • Measurement vs Measurement SystemMeasurement - value or dataMeasurement System - everything involved in performing the measurementmeasurement toolpart or sampleoperatorprocedureenvironmentGage R & R takes into account the entire measurement system, not just the measurement.

  • Measurement ResolutionThe resolution of a gage is the smallest unit of measure the gage is able to read.A gage should have a resolution of less than 10% of the total specification tolerance.Example: Specification: +/- 0.050Q: What is the maximum gage resolution?Total tolerance: 0.050 + 0.050 = 0.10010% of total tolerance: 0.100 * 0.10 = 0.010A: The gage should have a resolution of 0.010 or less.

  • Measurement VariationTotal Variation = Actual Part-to-Part Variation + Measurement VariationVariation can come from anywhere within the measurement system:Man (operator)MethodMaterial (part)MeasurementMachine (tool)Mother Nature (environment)

  • Exercise 1: Length of a PenGroup Size: 3 - 4 participantsMaterials: 6 plastic ruler, Exercise 1 in Student ManualTask: Record all possible sources of measurement variation if your group was asked to measure the length of pen.Duration: 10 minutes

  • Total Gage R & RThe total gage R & R of a measurement system is the final number calculated from a gage R & R study.Total gage R & R has two parts:Repeatability or Equipment Variation (E.V.)Reproducibility or Appraiser Variation (A.V.)

    Total Gage R & R = E.V.2 + A.V.2

  • Judging the Total Gage R & RIf Total Gage R & R is:< 20%: ACCEPTABLEBetween 20% and 30%: CONDITIONAL> 30%: UNACCEPTABLE

  • How to Plan and Execute a Gage R & R Study

  • PlanningThe typical gage R & R study uses2 or 3 operators10 partsEach operator will measure each part two or three times.In general, more data is better.

  • Selecting PartsDo NOT just select 10 parts at random!Samples should cover the full range of the specification and beyond.

    Example: Specification: 1.000 +/- 0.025Q: What should be the range of the samples?Full specification range: 0.975 - 1.025A: The samples should cover the full specification range and beyond, so they should cover approximately 0.950 to 1.050.

    Bonus Q: What should the gage resolution be for this case?

  • Tips for Data GatheringStay as close to the existing process as possible.Use a scribe to record data.Identify samples.Randomize the order of the samples for measurement.Do not round the data.

  • Time to take a

    BREAK!

  • How to Calculate a the Total Gage R & R for a Measurement System

  • Tips on the Gage R & R WorksheetBe able to perform all calculations by hand (a computer is not always available).Save a master copy of the blank spreadsheet (Read-Only).Shaded cells contain formulas. Enter data in white cells only.Record all background information at the top of first page of the worksheet.

  • Three Ways to CalculateMeasurement Unit AnalysisRaw calculation of the data.Percent Tolerance AnalysisRelates measurement variation to the specification.Product AcceptancePercent Study AnalysisRelates measurement variation to the total process variation.Process Control

  • Special CasesDiscrete data (go/no go, count, categorical)Checks for percent agreement among all operators.Goal: 100% agreementDestructive testing (torque, tensile strength)Instead of repeated measurements, subgroups of sequentially processed parts are used.Part variation within the subgroup should be minimized.

  • Exercise 2: Dowel Stick Gage R & RGroup Size: 3 - 4 participantsMaterials: Participant Kit, Student ManualTask: Conduct a gage R & R on the measurement system for one dimension of the dowel stick. The dimension to be measured will be assigned by the instructor. Duration: 45 minutes

  • Time to take a

    BREAK!

  • How to Improve a Gage R & R Result

  • Recall from earlier...Repeatability - Equipment VariationReproducibility - Appraiser VariationTolerance Analysis - Product AcceptanceStudy Analysis - Process Control

  • Improving a SystemHigh percent repeatability?Operator judgment / opinionAwkward sampleGage calibrationSpecificationHigh percent reproducibility?Operator trainingSample state or positionSpecification

  • Exercise 3: Dowel Stick Gage R & R (2)Group Size: 3 - 4 participantsMaterials: Participant Kit, Student ManualTask: Discuss how to improve the measurement system as it was used in Exercise 2. Confirm those improvements by performing a Gage R & R study on the new measurement system.Duration: 55 minutes (10 for discussion, 45 for Gage R & R)

  • Exercise 3: Dowel Stick Gage R & R (2)

    Percent Improvement =

    [(Exercise 2 Result) - (Exercise 3 Result)](Exercise 2 Result)

  • Time to take a

    BREAK!

  • Conclusion & Wrap-Up

  • ReviewThe theory behind gage R & R studiesHow to plan and execute a gage R & R studyHow to calculate the total gage R & RHow to improve the result of a gage R & R study.

  • ExamThere is an exam associated with this course!Date: x Month yyyyDuration: 90 minutesPassing Score: 80%

  • EvaluationsAnonymousPlease be candid!

    Thank you!!