Gage R & R Studies

The standard allows you to compare the R&R(error) with the Tolerance or the Process Variation or the Study Variation.

The need to compare the R&R with the Variation expected in the process arises because you need to know how good the instrument is to measure and make conclusions about the process.

Suppose you have a R&R/ Tolerance ratio that's good ( say , 10%) but also have a process capability that's very good, your actual process variation is much  tighter than the tolerance. In such cases you need to compare the R&R with the Process Variation ( 5.15 times the process sigma... if you go by the AIAG manual). The measurement system is ment to measure the actual process and needs to discriminate one job that the process produces from another . For the R&R study, it can be a good idea to pick up pieces that adequately represent the true variation in the process, and then look at the Ratio of R&R/Study Variation.

Ravi Khare

http://www.symphonytech.com