Gage Repeatability & Reproducibility for Continuous Data Instructor’s Name
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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
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
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
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!