How to resolve discrepancies in Level 3 PPAP supplier dimensional reports?

John Predmore

Involved In Discussions
#11
There are at least 2-3 functional dimensions which are out of spec by 0.02-0.05mm.
If the functional dimensions out-of-tolerance are position or geometric tolerances, and the GD&T all reference the same datum frame, this information could be a clue as to the problem. Are both metrology labs accessing the same datums? If the CMM fixtures the part on datum A and the OMM operator simply places the part on the glass, there could easily be a difference of 0.02 mm. If the features are circular, for example, you could easily get different results if the CMM touches a certain number of points and the OMM uses different points, best-fit-circle or manually selected points. Have your supplier take a picture or video of their measurement setup with your part for easy comparison - a picture is worth 1000 words.
 

Nath2892

Starting to get Involved
#12
If the functional dimensions out-of-tolerance are position or geometric tolerances, and the GD&T all reference the same datum frame, this information could be a clue as to the problem. Are both metrology labs accessing the same datums? If the CMM fixtures the part on datum A and the OMM operator simply places the part on the glass, there could easily be a difference of 0.02 mm. If the features are circular, for example, you could easily get different results if the CMM touches a certain number of points and the OMM uses different points, best-fit-circle or manually selected points. Have your supplier take a picture or video of their measurement setup with your part for easy comparison - a picture is worth 1000 words.
Thank you very much for your advise. Appreciate it.
 

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