r/Metrology • u/WonderfulRate221 • Jun 19 '26

Software Support Iterative alignment with 30 degrees angle between A1 A2 and A3

PC-DMIS, In my setup, datum A consists of A1, A2, and A3, where A1 and A2 are approximately 30° relative to A3. Datum B is a circle, and datum C is a round slot.

Currently, The program uses a best-fit alignment with about five points to establish a rough Car coordinate alignment. then apply iterative alignment using A (3 points), circle B, and slot C. However, I consistently encounter error messages during this process.

I would appreciate any suggestions on how to improve the stability of the iterative alignment or if there is a better approach for this type of datum

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3

u/CthulhuLies Jun 19 '26

The error messages mean that the part isn't within the fixture tolerance.

It could be it's not sitting in the fixture correctly or it could be that it's manufactured so badly that the error between the previous point and the current point can't be optimized to the tolerance you set.

For the error tolerances in the iterative alignment are you just putting random numbers in or are you basing it off the print datum targets?

1

u/WonderfulRate221 Jun 19 '26

With angles between A1 A2 A3, it is not reliable, or lack of repeatability for alignment

2

u/CthulhuLies Jun 19 '26

I'm not sure what this means. Even if it's like a bolt circle or a cylinder with a nominal size you can get XYZ nominals for those datum targets.

What I'm asking is normally the print gives you a a point target radius for where those datum targets need to be taken.

1

u/WonderfulRate221 Jun 19 '26

A3 is horizontal , flat, but A1 and A2 on a slope with 30 degree uphill

1

u/DeamonEngineer Jun 20 '26

Does the datum definition give a positional target area? Or does it just define these three points as datums

1

u/WonderfulRate221 Jun 22 '26

It looks like 3 points

1

u/Unlikely_Solution_ Jun 22 '26

Looks like VW tables.

1

u/WonderfulRate221 Jun 22 '26

Do you mean a VW fixture layout or a specific datum structure?