Statistics for Six Sigma Made Easy

C.11. From Chapter 17

RSS: Calculating the Sigma S from Multiple Parts Stack-Up S = the resultant assembly stack-up sigma s1, s2, s3, etc. = the sigma of each individual part being stacked Each sigma s is multiplied times 1.3 to allow for a long-term sigma drift. If each of n stacked-up parts has the same sigma s, then:

C.11.1. Use on Problem Type

If multiple parts are "stacked" in an assembly, the tolerances on those parts are likely to have been calculated using worst-case methods. Using the RSS method of calculating tolerances can open tolerances ...