I have a question on whether or not acustomer of ours is using appropriate sampling
method when it comes to accepting or rejectingone of our lots. Many of the parts we make
come from muli-cavity tooling. These are theones that generate more non-conformity reports with a needed corrective action response.

When a multi-cavity tool is approved into production we always furnish capability
studies of each individual cavity and shoot for a 1.67 CPK or > on the initial
sampling. Everything looks good up until we send in our first production lot where
the customer pulls 20 random samples pulling from several to all the cavities.
They crunch their results into a program that matches ANSI/SQCZ1.9-1993
Double Specification Limits, VariabilityUnknown - Standard Deviation Method, NORMAL (AQL-0.15%, S3), Sample Size = 20. Now by the randomness of
the samples and dispersion of the different cavity averages, this range when
applied to the program continually kicks out a small % either over or under spec
limit generating a non-conforming material report with a request for
corrective action. We are working with very limited tolerance of +/-.0008", so of
course we're splitting hairs here.

Is their method correct for this situation? This customer generates 70% of our sales, and I have a hard time with telling them that this may not be an appropriate
sampling method for the situation. This is starting to cause a slight animosity
between us. There may be some questions you would have before answering this completely, just e-mail me your questions and I'll answer them the best I can. Thanks for any help you can be on this matter.