Cpk for Hardness - PPAP rejected due to no Cpk value being given for a hardness

[Jim Wynne]

Re: Cpk for Hardness? PPAP rejected due to no Cpk value being given for a hardness

I agree totally, however our customer has recently adopted new standards of acceptance relative to PPAP review, and simply began rejecting submissions that previously would have been accepted.

Additionally, the parts in question are for a new product that were designed with GE&T and Hardness specs being listed as Special’s for the first time.

I understand that I am responsible for insuring our processes are capable, but instead of giving advice on what their acceptance standards are, I just get emails with demands for Cpk values on things like surface profile & ‘no burrs’.

Here you bring to light another thing to look out for in automotive work, and that's the phenomenon of customers moving the goalposts. In many cases, suppliers have done things that don't meet the requirements and assume that because a customer approved them (at least tacitly, in the form of a PPAP approval) that the customer will always approve them. Big mistake. It might not make any difference that the supplier did what made sense; when you're doing automotive work, you're not in Kansas anymore.

On the other hand, if a customer wants to change contractual agreements arbitrarily and in midstream, You have to consider the potential consequences--do something to placate the customer, or stand your ground and insist on what was agreed to.