A gauge repeatability and reproducibility study has several operators or tools measure the same parts several times, classically 10 parts, 3 appraisers and 2 or 3 trials, then uses ANOVA to split variation into part-to-part, repeatability and reproducibility. Results are reported as %GRR of total variation or tolerance: under 10 percent is good, 10 to 30 percent marginal, over 30 percent unacceptable. The number of distinct categories, which should be 5 or more, shows how many groups of parts the gauge can tell apart.
Gauge R&R came in at 34 percent of total variation. That CMM program can't feed SPC until the fixturing is fixed.
Pick study parts that span the real process range. Ten nearly identical parts make any gauge look terrible against total variation.
Also heard as
- GR&R
- gage R&R
- GRR
Related terms
Repeatability
Scatter in the readings when one person and one gauge measure the same part over and over with nothing else changed.
Reproducibility
Variation in measurement results when different operators, gauges or setups measure the same items.
MSA
Measurement systems analysis: the set of studies that prove a gauge is fit for the decisions its data will drive.
P/T ratio
Precision-to-tolerance ratio: measurement system spread as a fraction of the specification width.
Variance components
Breakdown of total variation into the shares contributed by each source, such as lot, wafer, site and measurement.