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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%