Gage Repeatability & Reproducibility for Continuous Data Instructor’s Name

Introductions Your Name Your Position What type of measurements you take in a given day

Agenda Introduction…………………..…..……(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? Accuracy –Calibration Precision –Repeatability (Equipment) –Reproducibility (Operator) Accurate, but not precise Precise, but not accurate

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

Measurement vs Measurement System Measurement - value or data Measurement System - everything involved in performing the measurement –measurement tool –part or sample –operator –procedure –environment Gage R & R takes into account the entire measurement system, not just the measurement.

Measurement Resolution The 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: +/ Q: What is the maximum gage resolution? Total tolerance: = % of total tolerance: * 0.10 = A: The gage should have a resolution of or less.

Measurement Variation Total Variation = Actual Part-to-Part Variation + Measurement Variation Variation can come from anywhere within the measurement system: M Man (operator) M Method M Material (part) M Measurement M Machine (tool) M Mother Nature (environment)

Exercise 1: Length of a Pen Group Size: participants Materials: 6” plastic ruler, Exercise 1 in Student Manual Task: Record all possible sources of measurement variation if your group was asked to measure the length of pen. Duration: 10 minutes

Total Gage R & R The 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 & R If Total Gage R & R is: ACCEPTABLE –< 20%: ACCEPTABLE CONDITIONAL –Between 20% and 30%: CONDITIONAL UNACCEPTABLE –> 30%: UNACCEPTABLE

How to Plan and Execute a Gage R & R Study

Planning The typical gage R & R study uses –2 or 3 operators –10 parts Each operator will measure each part two or three times. In general, more data is better.

Selecting Parts Do NOT just select 10 parts at random! Samples should cover the full range of the specification and beyond. Example: Specification: / Q: What should be the range of the samples? Full specification range: A: The samples should cover the full specification range and beyond, so they should cover approximately to Bonus Q: What should the gage resolution be for this case?

Tips for Data Gathering Stay 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 Worksheet Be 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 Calculate Measurement Unit Analysis –Raw calculation of the data. Percent Tolerance Analysis –Relates measurement variation to the specification. –Product Acceptance Percent Study Analysis –Relates measurement variation to the total process variation. –Process Control

Special Cases Discrete data (go/no go, count, categorical) –Checks for percent agreement among all operators. –Goal: 100% agreement Destructive 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 & R Group Size: participants Materials: Participant Kit, Student Manual Task: 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 Variation Reproducibility - Appraiser Variation Tolerance Analysis - Product Acceptance Study Analysis - Process Control

Improving a System High percent repeatability? –Operator judgment / opinion –Awkward sample –Gage calibration –Specification High percent reproducibility? –Operator training –Sample state or position –Specification

Exercise 3: Dowel Stick Gage R & R (2) Group Size: participants Materials: Participant Kit, Student Manual Task: 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

Review The theory behind gage R & R studies How to plan and execute a gage R & R study How to calculate the total gage R & R How to improve the result of a gage R & R study.

Exam There is an exam associated with this course! Date: x Month yyyy Duration: 90 minutes Passing Score: 80%

Evaluations Anonymous Please be candid! Thank you!!