Calibration Issues

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  • Calibration Issues

    The thing is, I'm not sure what the issue is. I've been noticing a trend of increasing STD DEV after calibrating a variety of probes. I recently calibrated a 5X100MM probe tip and got a STD DEV of .0039". This isn't normal by any means. I also noticed that the THEO vs MEAS values are exactly the same, which is impossible.

    Probe file=5X100MM Date=1/24/2020 Time=7:34:22 AM

    qual sphere CENT X 356.6455 Y 377.2350 Z-483.5792 D24.9858
    T1A0B0 THEO X 0.0000 Y 12.0000 Z 300.4600 D 5.0000
    T1A0B0 MEAS X 0.0000 Y 12.0000 Z 300.4600 D 5.0000 PrbRdv 0.0012 StdDev 0.0039



    Has this happened before? What was the cause and solution for you?

  • #2
    If you're using a probe like LSPX, SP600 (...), the actual is always the same than the theo. Getting the real actual consist in subtracting the prbrdv (probe radius deviation).
    If your 5x100 gives bad std dev, maybe the stem is broken or unclamped, or the ball is unstuck.

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    • #3
      If you're using a probe like LSPX, SP600 (...), the actual is always the same than the theo.
      This is only true for the diameter. If you look at the calibration results, you can see that there is a line for the qual sphere. This indicates that the user answered YES when asked if the qual sphere had moved. If you answer YES to that message then you are essentially re-defining the qual sphere position and setting your first tip as master so the measured and theos for all values except prbdev & stdev should be identical.
      Neil Challinor
      PC-DMIS Product Owner

      T: +44 870 446 2667 (Hexagon UK office)
      E: [email protected]

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      • JEFMAN
        JEFMAN commented
        Editing a comment
        Right, I was talking about diameter only...
        Reset to theo values does the same (except the sphere location !)

      • ALousyUser
        ALousyUser commented
        Editing a comment
        You are right. I clicked "NO" when asked if the qual sphere has moved. This helped improve the STD DEV to 0.0009". Isn't the standard accepted STD DEV 0.0004" or less?

    • #4
      THEO and MEAS values for the master tip must ALWAYS be EXACTLY the same on x,y,z and a slight diameter difference is expected. When this is not true you've had an error in calibrating probes.

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      • #5
        Originally posted by Douglas View Post
        THEO and MEAS values for the master tip must ALWAYS be EXACTLY the same on x,y,z and a slight diameter difference is expected. When this is not true you've had an error in calibrating probes.
        OR you have told it to calibrate the master probe and told it NO the sphere has not moved.

        THIS is ASSuming that you are using a rack & master probe setup. If you are NOT using a rack & master probe setup and you tell it NO the sphere has not moved, then the A0B0 tip will show XYZ deviations.
        sigpic
        Originally posted by AndersI
        I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

        Comment


        • Douglas
          Douglas commented
          Editing a comment
          I believe even with a fixed probe on a motorized wrist this is the case also as long as you always use the same tip to check the ball... you just gotta lie to pcdmis tell it the ball moved when you calibrate your mater tip to maintain proper correlations. it is a poor wording weakness in pcdmis

        • Matthew D. Hoedeman
          Matthew D. Hoedeman commented
          Editing a comment
          IF you are using a rack & master probe. I have no rack, nor a master probe. So if it is the second build for the day, and i tell it NO the sphere hasn't moved, then the A0B0 will have deviations. It isn't a problem in anyway, shape, or form, if you are NOT using multiple probe builds at once.

        • Douglas
          Douglas commented
          Editing a comment
          correct, improper probe correlations do not matter until you use them both

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