W
I just had another PPAP rejected due to no Cpk value being given for a hardness requirement that was designated as a Special Characteristic on the customers drawing. What I did supply was a certification & test results from the approved supplier we use for heat treating, along with our own test results.
They also said we have no documented control for this Special Characteristic. Our Control Plan specifies certification from the supplier along with recorded receiving inspection on each lot.
I am no expert on these matters by any means, but just how does one go about calculating Cpk for material hardness?
TIA
Bill
They also said we have no documented control for this Special Characteristic. Our Control Plan specifies certification from the supplier along with recorded receiving inspection on each lot.
I am no expert on these matters by any means, but just how does one go about calculating Cpk for material hardness?

TIA
Bill