Gage Repeatability & Reproducibility (GRR)

• Gage R&R (Gage Repeatability and Reproducibility) studies determine how much of your observed variation is due to the measurement system i.e., GRR helps to assess the Repeatability & Reproducibility of the Measurement System.
• Gage R&R emphases on two key characteristics of measurement:
  - Reproducibility: The variation contributed due to Appraisers (measuring people)
  - Repeatability: The variation due to Measurement Gage or poor Gage design
• Depending on data availability and data type, the gage R&R are categorized into:
  - Crossed gage R&R
  - Nested gage R&R

• Minimum 10 parts to be measured
• Select at least two technicians or operators to measure the parts
• Each operator or technician must measure each part two or three times
• Collect the measurement in random order

• Used only in non-destructive testing & assumes all parts can be measuredmultiple time

• Used when Destructive Testing/ Where repeated measurement is not possible. It must have a balanced design with random factors.

• A quality engineer chooses ten parts that represent the process variation's expected range. Then, in random order, three operators measure each of the ten parts three times. To examine the variability in measurements from the measurement system, he conducts a gage R&R study - crossed.

• Step1: Conduct Gage R&R study crossed
  Note: When measuring, if the product is destroyed or damaged or sacrificed then we have to use R&R Nested. For example, Hardness Testing

• Step2a: : Interpretation – 2 Way Anova
  - P-value (0.071) for the operator (Without interaction) is greater than 0.05, implies that operators do not contribute significantly for the measurement variation
  - P-value (0.00) for the Part (With & Without interaction) is greater than 0.05, implies that Part contribute significantly for the measurement variation
  - Here P-value (0.951) for the Part and Operator interaction is greater than 0.05. Hence, Minitab generates a second twoway ANOVA table that omits the interaction from the final model

• Step2b: : Interpretation – Variance Components
  - Variance component table is to compare the variation from each source of measurement error to the total variation.
  - Here Part-To-Part variation is 99.18% and the Total Gage R&R, i.e. 0.82% indicates variation is mostly due to difference between the parts
  - Total Gage R&R is 0.82% indicates the measurement system is acceptable

• Step2c: : Interpretation – Gage Evaluation
  - Gage evaluation table is to compare the measurement system variation to the total variation
  - Here Total Gage R&R is 9.07%; thus measurement system is acceptable
  - NDC is 15, indicates the measurement system can detectthe difference betweenthe parts

• If the Total Gage R&R percentage in the %Study Var column(%Process) is:

• • If you are looking at the %Contribution column, the corresponding standards are: