We tried measure Pb, Ag, and Cu % content with the arc spark spectrometer using the same set of sample ingot from our process. The ANOVA method for destructive GR&R were used with 10 samples and 3 operators. (I doubt if this kind of measurement has the component of operator error indeed, because there is no fixture required in the measurement.) Nevertheless, the outcome %P/T is around 26 with spec. range 0.2%.
I think it could still be considered acceptable and my colleague is sending the results to customer for comment. I believe the uniformity of the sample content is important because the same spot can not be measurement repeatedly.
At the same time, Ppk has been done with result >1.66. I think it can also be supporting to the less-than-best GR&R results.
Btw, if the spec. range for Pb, Ag, and Cu are different, should I just do GR&R on the one with the smallest range ?