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Adding Probe Angles AFTER Calibration Sphere has been moved

CarbideEVO
Good morning everyone,

After searching the forum (seems using google to do it gets better results!), I can't find a clear answer to this question that has been asked many times Confused Rolling eyes :

After calibrating A0B0, and additional angles - If I move the sphere, but discover I need additional angles, I would recalibrate all previous angles, and the new angles.

However, I read people saying this is unnecessary - as long as I recalibrate A0B0, and select "Yes, the sphere has moved" (because it has!), and measure the NEW angles..

that the previously calibrated angles and the newly added angles will all related to each other.

Is this true? Is this explained in the help file? What is the source of your information?

Thank you for your time!


  • Is this true? Is this explained in the help file? What is the source of your information?



    1 : I would say that it's not totaly true...
    If you use a "master probe" to give the new location of the sphere, you will obtain nice results.
    I don't say "accurate" but "nice" :
    Offsets of a tip angle describe the vector between the actual tip and the tip which was used the last time that you said "yes, the sphere moved".
    If you move again the sphere, then you will use a new "master tip", and the new angles calibrated will define offsets from it.
    If you use the same "master tip / master probe", then the results should be accurate, except if you homed the cmm many times since the first sphere moved.

    2 : I don't know

    3 : here + some years of using / trying to understand.

    In addition, if you want a real accuracy, you should calibrate all angles at the same time.
    If you want a high accuracy, you should calibrate each tip with autocalibrate just between rotation and measure. It's very long, but it avoids uncertainty of re-positionning of the head.
  • Yes you are correct, just calibrate A0B0 and your new angle, however I need to ask you if this A0B0 is your master probe (or master probe angle)?

    Whether your move your sphere or not, you should only answer yes manual or yes dcc with your mater probe (or master tip). Generally most people use a master probe (in A0B0 of course) and have no other angles on that probe. The master probe is used only for finding the cal sphere and not measuring. This is not set in stone so if you have to use your master probe to measure, then use it. If you need to make an angle on your master probe, then do it.

    The work flow is the same for a master probe in A0B0 only and other probes with angles. So I have a probe that has angles and I already calibrated it but i need another angle. I just load my master probe, answer yes manual or yes dcc, calibrate the master probe, then load my probe that has a new angle and calibrate that new angle only, and i'm done.
  • So your question is dependent upon how your machine's probe calibration is currently managed.

    In my personal opinion, which is utilizing an (over) abundance of caution:
    If you need to add probe angles after the cal sphere has moved, you should re-calibrate your master probe at T1A0B0 with cal sphere re-installed, then calibrate ALL angles of ALL probes again, including the new angles.

    However, according to hexagon support page link here: (you'll have to log in to open the PDF)
    https://support.hexagonmi.com/s/arti...=1577986104849

    Example 2 directly answers your question: it says you can get away with re-calibrating only the master tip and the new angles.

    (excerpt from pdf file)
    Example / Procedure
    1 Master Probe is Replaced / Recalibrate all probes
    2 Add a new Tip Angle to an existing probe / (Recalibrate the Master Tip*) and then the new Tip Angle
    3 Probe 5 was crashed & replaced / (Recalibrate the Master Tip*) and then Probe 5
    * If the CMM was rehomed or the Qual Sphere moved.
  • So your question is dependent upon how your machine's probe calibration is currently managed.

    In my personal opinion, which is utilizing an (over) abundance of caution:
    If you need to add probe angles after the cal sphere has moved, you should re-calibrate your master probe at T1A0B0 with cal sphere re-installed, then calibrate ALL angles of ALL probes again, including the new angles.

    However, according to hexagon support page link here: (you'll have to log in to open the PDF)
    https://support.hexagonmi.com/s/arti...=1577986104849

    Example 2 directly answers your question: it says you can get away with re-calibrating only the master tip and the new angles.



    This is exactly what I was looking for, thank you

    As I saw in the other threads, it seems everyone has a strategy or opinion that differs a little. I guess the safest unquestionable thing to do is continue calibrating all probe angles, however, it may not be necessary in some circumstances.

    I do not work in a production environment, so probes configurations are changing daily, and new challenges require new angles! Slight smile Thank you all!

  • in reply to CarbideEVO
    the last thing you want is to produce data with skewed results because you tried to cut a corner and save 15 minutes. if you calibrate the master probe and just the new angles, the likelihood of the existing probe angles not correlating with the new ones (or being shifted from the master) is bound to be higher.

    If you calibrate all a once, this uncertainty of whether or not all your probes correlate, is mitigated entirely.
  • in reply to CarbideEVO
    I didn’t know that. I guess calibrating only ur new angles is only good to prove u won’t crash into the part or prove u can reach what ur trying to probe. Better to calibrate then all.


  • This is exactly what I was looking for, thank you

    As I saw in the other threads, it seems everyone has a strategy or opinion that differs a little. I guess the safest unquestionable thing to do is continue calibrating all probe angles, however, it may not be necessary in some circumstances.

    I do not work in a production environment, so probes configurations are changing daily, and new challenges require new angles! Slight smile Thank you all!




    Took me 9 probe tips to get 95% of the jobs done. Low to no production. Seriously, sit down and think about it you might realize it only takes a few and every now and then you might have to build a 'custom' non standard tip. The size of your CMM doesn't change.
  • if you calibrate the master probe and just the new angles, the likelihood of the existing probe angles not correlating with the new ones (or being shifted from the master) is bound to be higher.


    IF the master probe is always kept at nominal offsets (only 'calibrated' with "YES, the sphere has moved") and all the other tips/angles are calibrated with "NO, the sphere hasn't moved"), the 'level of uncertainty' is the same for all tips/angles (=one measurement of the datum sphere + one calibration) even if you don't calibrate them all at the same time. Of course, the uncertainty could go in different directions from one localisation of the datum to the next, but for normal use cases this should be enough.
  • in reply to AndersI
    Given you are in a controlled environment and nobody altered the current state of your probes (bends or other possible contributors to unexpected variation since that probe's last calibration), correct?

    If you have the CMM in a room that varies 10°F daily, and have sixteen (high turnover) operators running the machines 24/7, the chances of additional variation between probe calibrations caused by either damage or environment -that could be mitigated by a full probe cal- are certain.
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