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Strange Scan behavior (wobbly scan path)

I have some strange scan behavior where two machines behave differently.
Maybe some of you can give me some insight why this might be happening.

We have two machines of the same type. Both Tigos with a fixed scanning head (HP-S-X1-C).
Both recently (last half year) calibrated by Hexagon. The only difference is that one is old (9 years old) and the other one is new (1 year old).

The weird thing happens when I scan a plane using the basic circle scan method with the type set to "plane".
With the old machine, everything is fine. I get smooth (circular) scans.
With the new machine, I get weird wobbly scans. The machine doesn't follow a nice smooth path.
When I evaluate the flatness of the plane both evaluate the same (0.016mm).

old machine, smooth scanpath 

new machine, wobbly scanpath

This test was done with the same program (same parameter settings), same part (not taken out of the fixture) and same probe.
Both machines use PC-DMIS 2023.2 (but slightly different SP).

settings

I did further tests on ring gages and calibration spheres evaluating roundness and diameter.
Both machines get great values well in the machine's tolerance (mostly under 0.001mm).
Here the new machine with the wobbly plane scan even gets better results than the old machine.
On these scans I also don't see any wobbling.

Does anyone have any Ideas why the new machine can't follow a nice circular plane path?
Can I do something to improve this?

Parents
  •    &  

    Thank you for your replies and sorry for not answering earlier.

    50 pts/mm is the standard we use on all of our CMMs.

    I did evaluate the roundness of the plane scan. On the "good" machine it is around 0.02mm... On the "bad" machine up to 0.15mm.
    The deviation is always on the same quadrant.

    I also came in one night when no other production machine was running to rule out a vibration problem.

    Doing a lower matrix calibration will be the next thing to do.
    Unfortunately we have higher priority projects at the moment so it will take a while before doing this.

Reply
  •    &  

    Thank you for your replies and sorry for not answering earlier.

    50 pts/mm is the standard we use on all of our CMMs.

    I did evaluate the roundness of the plane scan. On the "good" machine it is around 0.02mm... On the "bad" machine up to 0.15mm.
    The deviation is always on the same quadrant.

    I also came in one night when no other production machine was running to rule out a vibration problem.

    Doing a lower matrix calibration will be the next thing to do.
    Unfortunately we have higher priority projects at the moment so it will take a while before doing this.

Children