"Also can GRR be performed based on Cpk values?" if I have interpreted your question correctly - you cannot use Cpk to determine Gage R&R. Measurement error and and actual product variation are confounded together. you must use a designed approach to separate the two to determine the components of measurement error and product variation.
Thanks for your inputs. I agree that Cpk values cannot be used for GRR studies, but what really I wanted to know is can Cpk values give some guidelines about the the measurement systems. Example:
Case 1: Process with Cpk=2
case 2: Process with Cpk=1
Ques.1.
Can I say with some confidence, keeping in mind the inverse relation between Cpk and GRR, that if I have to prioritize GRR, I should do GRR study for case 2 first than case 1.
Ques2.
Also If the %GRR calculation for case 1 is slightly over the line , say 35 %, can we just pass this gage based on good Cpk value. What if, case 2 gives %GRR=35 %, should we fail this gage because of poor Cpk value.
Thanks guys,