Gage R&R

Overview | How to | Example

 


 

Overview

The Gage Repeatability and Reproducibility study helps you to determine how much of the observed process variation is due to measurement system variation. It breaks down the overall variation into variation due to part-to-part, repeatability and reproducibility. The ANOVA method is commonly used as it also breaks fown reproducibility into operator and operator by part interactions. This tool can be used on crossed Gage R&R studies at which each part is measured by each operator several times.

The following are some guidances to set up a Gage R&R study.

 


 

How to

At the Excel Menu (For Excel 2007, go to Add-ins first)

  1. Choose ProcessMA > Quality Tools > Gage R and R > Gage R and R

  2. In Measurement, select the column containing measurement data (Numeric)

  3. In Part, select the column containing part indicators (>=2 distinct values)

  4. In Operator, select the column containing operator indicators

  5. In Method of Analysis, choose the method to use for analysis. The Xbar and R method distinguishes the observed process variation into part-to-part, repeatability and reproducibility components. The ANOVA method is similar but it also breaks down reproducibility into operator and operator by part components

  6. In Study Variation, enter a value to be used to calculate Study Variation. The default is 6, which is the number of standard deviations needed to capture 99.73% of your process measurements (Optional, Numeric, >0)

  7. In Process Tolerance, enter the tolerance range (USL - LSL) if known (Optional, Numeric)

  8. Click OK

 

 

Example

Three operators took measurements on 10 parts, twice on each part. You want to determine how much of the observed process variation is due to measurement system variation.

  1. Open data worksheet by choosing ProcessMA > Tools > Data

  2. Choose ProcessMA > Quality Tools > Gage R and R > Gage R and R

  3. In Measurement, select AQ - Measurement

  4. In Part, select AR - Part

  5. In Operator, select AS - Operator

  6. Click OK

 

Results & Interpretation

By looking at %VarComp, the variation due to differences between parts (Part-to-Part) contributes 94.1% to the overall variation. It is much larger than that of the Total Gage R&R at 5.9%. The same observation can be made by looking at the Component of Variation Chart. This indicates that measurement system error is small. From the By Part Chart, the variation of the red line shows that there are significant differences between parts. On the other hand, from the By Operator Chart, the red line is relatively flat, which indicates that the differences between operators are small. In addition, most of the points in the Xbar Chart for Measurement by Operator are out-of-control, indicating that variation is mainly due to differences between parts.

 


 

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