Quick and Easy Continuous Variable Gage R&R Test

Looking for something to do? Why not run a continuous variable gage repeatability and reproducibility test? Our experience is that while many organizations have their key measurement devices on a calibration schedule, calibration simply isn’t enough.  Gage R&R tests provide insights into how the users interact with measuring equipment and can uncover issues such as: bias, linearity issues, accuracy issues, and of course, repeatability and reproducibility issues.  

The quick and easy way to run a continuous variable gage R&R test is to ask several operators to measure the same parts several times each.  Including a part with a known size, allows you to check for accuracy.

There are sophisticated tools for analyzing the results, but the quick and easy way is to make a scatter plot of the results as well as an X-bar and R chart.  This approach works well in most circumstances.

The results might look as follows (Part No. 3 has a known size of 1.00 inches):

Gage R and R What issues has our quick and easy gage R&R test uncovered:

  • There appears to be an accuracy issue.  Part number 3 has a known size of 1.000” but the operators are measuring it to have an approximate size of 1.106” on average.
  • There appears to be a linearity issue.  As the part size gets bigger, the range of the measurements generally gets bigger.
  • There appears to be an unusual issue that the first measurement is always the smallest, the second measurement is larger, and the third measurement is the largest.
  • There also appears to be a repeatability issue.  The range of the measurements is a bit large. 

The criticality of the measurement system and the part dimension would determine which issue we would tackle first.  But we gained a lot of insight from a quick and easy test!