Different Probe Calibration Results

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  • #1

    Different Probe Calibration Results

    Still testing the same part on 2 identical CMMs and getting different results. Fixed analog heads. Same probe builds. Same probe calibration parameters. CMM A is my older CMM And CMM B is my newest one.

    Inches
    CMM A 3X95 STD 0.00037
    CMM B 3X95 STD 0.00005

    ​​​​​​CMM A 5X100 STD 0.00027
    CMM B 5X100 STD 0.00005

    ​​​​​​CMM A 4X40_BACK STD 0.00030
    CMM B 4X40_BACK STD 0.00005

    ​​​​​​CMM A 4X40_FRONT STD 0.00025
    CMM B 4X40_FRONT STD 0.00005

    Is this a contributing factor to my differences in measurement results?
    Tags: None
  • #2
    Well each CMM comes with a measurement uncertainty, better shown on calibration results. It is normal to see a few microns of difference between machines. If this is acceptable to you, depends on the application and field of manufacturing :P

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    • #3
      Fixed probe head, but what's the probe? Are you using TP20s? You could be seeing a module going bad.

      EDIT: Actually, I'm now thinking TP200 as it's happening to all of theprobes.

      Comment

      • #4
        Originally posted by Lee.drt View Post
        Fixed probe head, but what's the probe? Are you using TP20s? You could be seeing a module going bad.

        EDIT: Actually, I'm now thinking TP200 as it's happening to all of theprobes.
        Its a LSP style scanning head.

        Comment

        • Lee.drt
          #4.1
          Lee.drt commented
          05-24-2022, 10:58 AM
          Editing a comment
          Did you swap the physical stylus constructions (from puck on down) and see if that follows?
      • #5
        Originally posted by constadin View Post
        Well each CMM comes with a measurement uncertainty, better shown on calibration results. It is normal to see a few microns of difference between machines. If this is acceptable to you, depends on the application and field of manufacturing :P
        Some measurements are off 0.001" or more. I have tolerances that are +/-0.0005"
        Last edited by acgarcia; 05-24-2022, 11:00 AM.

        Comment

        • #6
          5X40s are L shapped probes, 1 facing Y- and other facing Y+. I'm checking diameters along they Y axis of the CMM and I get 2 different readings on the same part. For example.

          CMM A Dev -0.0004
          CMM B Dev 0.0004

          CMM A Dev -0.0008
          CMM B Dev 0.0006

          CMM A Dev -0.0006
          CMM B Dev 0.0019

          These are taken with a probe straight down in A0B0.

          CMM A Dev -0.0007
          CMM A Dev -0.0000

          CMM A Dev -0.0006
          CMM B Dev 0.0008

          CMM A Dev -0.0007
          CMM B Dev 0.0023

          Comment

          • #7
            acgarcia I'm not sure what the part looks like. Would a timing mark help with putting the part in the same place on both of the machines. Hope this helps.
            Whoops your just trying to calibrate your probe tips. I thought you were trying to measure a part on both machines.
            Last edited by ogcharliebrown; 05-24-2022, 11:38 AM.
            2024 can't get here soon enough!!!

            Comment

            • #8
              Are you using the same artifact to calibrate on both CMMs? We had two reference machines side by side that wouldn't pass an R&R until we calibrated both machines using the same artifact.

              Comment

              • #9
                Originally posted by ogcharliebrown View Post
                acgarcia I'm not sure what the part looks like. Would a timing mark help with putting the part in the same place on both of the machines. Hope this helps.
                Whoops your just trying to calibrate your probe tips. I thought you were trying to measure a part on both machines.
                Yes, i'm measuring the same exact part on 2 identical CMMs. My first post was about their probe calibrations and my last post was a few measurements of the same part being checked on it. The difference in measurement deviation between the 2 CMMS.

                Comment

                • #10
                  Originally posted by Sora5 View Post
                  Are you using the same artifact to calibrate on both CMMs? We had two reference machines side by side that wouldn't pass an R&R until we calibrated both machines using the same artifact.
                  So I went to check the diameters of my cap spheres to check sizes and my older CMM had the cal sphere loose. It wasn't hand tight. Let me re do the lower matrix and re calibrate the probes and see out the results come out.

                  Ceramic cal sphere diameters are 24.994 90mm and 24.993 45mm.
                  Last edited by acgarcia; 05-24-2022, 12:19 PM.
                  • Likes 3

                  Comment

                  • NinjaBadger
                    #10.1
                    NinjaBadger commented
                    05-24-2022, 12:11 PM
                    Editing a comment
                    That'll be it most likely!
                  • acgarcia
                    #10.2
                    acgarcia commented
                    05-27-2022, 03:04 PM
                    Editing a comment
                    Results are still different after tightening the cal sphere and re running the lower matrix.
                • #11
                  Originally posted by acgarcia View Post
                  5X40s are L shapped probes, 1 facing Y- and other facing Y+. I'm checking diameters along they Y axis of the CMM and I get 2 different readings on the same part. For example.

                  CMM A Dev -0.0004
                  CMM B Dev 0.0004

                  CMM A Dev -0.0008
                  CMM B Dev 0.0006

                  CMM A Dev -0.0006
                  CMM B Dev 0.0019

                  These are taken with a probe straight down in A0B0.

                  CMM A Dev -0.0007
                  CMM A Dev -0.0000

                  CMM A Dev -0.0006
                  CMM B Dev 0.0008

                  CMM A Dev -0.0007
                  CMM B Dev 0.0023
                  So above is my measured data from both CMMs. Same program was copied over a few weeks ago. Could it just be that the program sucks?

                  Comment

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