Re: Inspection of Diameters on a CMM
Wow. You have a lot of issues.
First, you have recognized you have to control the temperature. Is there any commitment to control the measurement lab temperature? The temperature that the measurement is taken should be reported for a material that you describe. If you can not control it, you need to have a temperature factor - Coefficient of Thermal Expansion is nice on straight pieces, but circular features may not expand perfectly. So, you may need a dimension to temperature study if the labs are not committed to measuring at a tight temperature tolerance.
Then, there is the control plan measurement problem. Yes, they signed off on your control plan by approving your PPAP, and really it should be their responsibility to verify other labs are using equivalent measurement techniques, but it does fall in the cracks from time to time. Your situation sound like more of a routine than accident, though. Sounds like the customer is not committed to lab-to-lab variation issues. That is going to be a tough one to resolve without some irritation.
If it was not for all of that, a CMM should be applicable, if they take enough points in enough places to ensure an adequate measurement and report it in the correct manner (MMC? Average Dia?)
Without some agreement on all of the issues, you are going to be fighting this forever.