Datum Alignment from Fixture Tooling

[[Do...]]

Has anyone ever encountered a scenario where you have a CMM fixture that locates the part on the physical datums and has tooling balls located on the fixture for CMM pickup? In this situation how do you program the part so that it aligns properly and can provide measurements that correlate back to the required datums if you are not able to physically probe the actual datum features? Secondly, has anyone encountered a situation where the CMM fixture located on the physical datums, preventing actual probing, and it did not have tooling balls for CMM pickup? How do you program the part from this setup? Lastly, is there any literature out there that is available that helps describe and provide detailed steps on how to develop CMM programs where you have to use tooling balls for part alignment and measurement?

[[Ch...]]

You can put in a programable stop and take the part out of the fixture and then measure on the datum locators.

 

[[Do...]]

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How would you do it if you had tooling balls?

[[Ke...]]

The CMM fixture(s) that I had to use that had tooling balls also had XYZ coordinates for those tooling balls, and I used those in a 3D Best Fit Base Alignment. For those parts, the results were reported "in-body position" (automotive), so the datums themselves did not need to be measured... I suppose that if the tooling balls do not have xyz coordinates, you can measure the fixtures simulated datum features as the Base Alignment and then report the xyz of the tooling balls, yourself (definitely need to be sure of your measurements/repeatability). However, I would think that the fixture manufacturer should be able to provide those tooling ball coordinates for you(?)

[[Do...]]

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This makes sense. Can you share the steps on how to take the XYZ coordinates from the tooling balls and plug them into the 3D Best Fit Base Alignment characteristic? I have never encountered this situation, so I am uncertain of the proper steps.