Calibrating Probe Tips

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  • Calibrating Probe Tips

    I have been hearing at my work that selecting "Yes (DCC hits to locate tool)" is not an accurate way to calibrate the Master Probe. This person states the only way to calibrate the Master probe is to take a manual hit on top of the sphere to locate the calibration sphere. Of course you have to select "Yes (Manual hit to locate tool) to achieve this. My CMM DOES support the ability to locate the qualification tool using DCC hits. My question is can I select "Yes (DCC hits to locate tool) for my master probe without loosing accuracy? A little more info on the calibration sphere...I do have to remove it after I calibrate tips because the size of our CMM table, BUT I screw it in to the same location every time, so the position change of the Cal sphere is very small.

  • #2
    The delta may be small, but it is going to be factored in to every probe.

    If you cal A0 B0, take the ball off, put it back and cal A90 B0, if the ball is .001" in a different place, all measurements between A0 B0 and A0 B90 will be off by .001" because of the calibration, regardless of what the actual part is off.

    You do not need to use a manual hit. If the ball is sufficiently close to where it was, Yes (DCC hits to locate) with the master probe, then No on all probes you will use before you remove the sphere.

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    • #3
      I certainly agree with you. Just looking for a double check. It seems PC DMIS put this as an option for an application exactly as I have...so I don't have to take manual hits on the cal sphere so often. Thanks

      Comment


      • DAN_M
        DAN_M commented
        Editing a comment
        The very first time you ever screw the sphere into the table, take the manual hit. If you put the sphere away, but take it back out and always use the same hole to screw it in at, then using DCC Hits on the MASTER and then saying NO to all other tip positions will properly relate everything back to your MASTER and you'll be all set. This is what I've done for years, never had an issue.

    • #4
      Originally posted by Caemgen View Post
      The delta may be small, but it is going to be factored in to every probe.

      If you cal A0 B0, take the ball off, put it back and cal A90 B0, if the ball is .001" in a different place, all measurements between A0 B0 and A0 B90 will be off by .001" because of the calibration, regardless of what the actual part is off.

      You do not need to use a manual hit. If the ball is sufficiently close to where it was, Yes (DCC hits to locate) with the master probe, then No on all probes you will use before you remove the sphere.
      +1 agree.

      Oh HI DanC@GA!!!!!!!!! Nice to finally see you on here. Welcome to the forums.
      PcDmis 2015.1 SP10 CAD++
      Global 7-10-7 DC800S

      Comment


      • #5
        I don't like the writing in the Online Help (my emphasis) - I want to know the reasoning behind that statement. As it is written now it's "Cargo Cult programming":

        DCC+DCC mode functions like the MAN+DCC mode except that instead of taking the first hit manually for each tip, PC-DMIS instead takes DCC sampling hits to locate the sphere. You may find this mode useful if you want to fully automate the calibration process. However, be aware that the MAN+DCC mode may give more accurate results.
        Yes, the first time calibration of a probe file (or one you have Reset to theos) may need manual hit(s), because the theoretical offsets may not match physical reality exactly and the probe head may not be perfectly square to the CMM axes, but as long as the probe have been previously calibrated and the datum sphere is screwed back in the same place, I really can't see why MAN+DCC would get a 'better' result than DCC+DCC? Please enlighten me!

        The cosine error of a manual point will probably be as large, or larger, than that of the DCC sampling points, so what else is there that could affect this?
        AndersI
        SW support - Hexagon Metrology Nordic AB

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        • #6
          To all newbies and beginners and even ones who have been doing this for awhile. Never ever ask your boss a PC-DMIS question. Come on here from now on, from my experience, your boss or others claiming they know PC-DMIS, THEY DO NOT KNOW, They only claim to know, to get their job. If they knew PC-DMIS, they would be writing programs and you wouldn't be working there.

          With that said, You have 3 options in PC-DMIS, Why? because all 3 options work in their own way.

          1: No - You have not moved that Sphere at all

          2: Yes - Manual hit That Sphere isn't even close to where it was before or you don't remember where it was the last time.

          3: Yes DCC That Sphere is pretty close to where it was before, it will take 4 hits on that Sphere to center it, and then start the Calibration. If it fails to take the 4 hits it will NOT continue, then you can use the second option
          (In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)
          They say "Nobody's Perfect." I must be Nobody.

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          • WolfMan
            WolfMan commented
            Editing a comment
            spot ON. IMO both DCC and MAN YES, do exact same thing.

          • WolfMan
            WolfMan commented
            Editing a comment
            The major difference b/n the NO and YES, is that when YES is selected it will sync all the probes to the first A0B0. That is why DCC yes just as good.

        • #7
          I would like to NOT HAVE TO re-calibrate all my stylus' each time I add a new tip angle!

          Would be nice if I could....1. Place the sphere close to original position, 2. Calibrate the Master, 3. Calibrate new tip ONLY, 4. Continue running production with all available synchronized stylus'.

          From what I understand this is not possible, they will not be synchronized. Due to the lack of real estate I cannot have the sphere in the same spot. I dread whenever I have to go thru this process, our automated cell has to stop every time I calibrate and everything is waiting on the CMM.
          Last edited by Kp61dude!; 10-25-2017, 10:47 AM.
          PcDmis 2015.1 SP10 CAD++
          Global 7-10-7 DC800S

          Comment


          • #8
            Originally posted by Kp61dude! View Post
            I would like to NOT HAVE TO re-calibrate all my stylus' each time I add a new tip angle!

            Would be nice if I could....1. Place the sphere close to original position, 2. Calibrate the Master, 3. Calibrate new tip ONLY, 4. Continue running production with all available synchronized stylus'.

            From what I understand this is not possible, they will not be synchronized. Due to the lack of real estate I cannot have the sphere in the same spot. I dread whenever I have to go thru this process, our automated cell has to stop every time I calibrate and everything is waiting on the CMM.
            It is my understanding (I've never tested it myself) that having a MASTER PROBE is just for what you describe.

            1) Locate the qual tool with the MASTER PROBE at A0B0 (YES, moved)
            2) Calibrate all other angles and probe files (NO hasn't moved)
            3) Remove the qual tool
            4) Put the qual tool back on the table, 100mm from where it was
            5) calibrate the MASTER PROBE at A0B0 (YES, moved)
            6) ALL previously calibrated angles and probe files are still in relationship to the MASTER PROBE
            7) ADD the angle/probe needed, calibrate just it (NO hasn't moved)
            8) NEW is in relationship to all previous calibrated.
            sigpic
            Originally posted by AndersI
            I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

            Comment


            • DAN_M
              DAN_M commented
              Editing a comment
              Exactly my understanding as well.
              But expanding that logic....

              I often have to put the sphere back in it's case but when its out I always use the same hole to screw it into. So, I never click "NO"....I always locate my master with DCC hits and then say "NO" to everything else and it all relates back to the master for me.

          • #9
            Originally posted by Matthew D. Hoedeman View Post

            It is my understanding (I've never tested it myself) that having a MASTER PROBE is just for what you describe.

            1) Locate the qual tool with the MASTER PROBE at A0B0 (YES, moved)
            2) Calibrate all other angles and probe files (NO hasn't moved)
            3) Remove the qual tool
            4) Put the qual tool back on the table, 100mm from where it was
            5) calibrate the MASTER PROBE at A0B0 (YES, moved)
            6) ALL previously calibrated angles and probe files are still in relationship to the MASTER PROBE
            7) ADD the angle/probe needed, calibrate just it (NO hasn't moved)
            8) NEW is in relationship to all previous calibrated.
            Thanks so much for your input. I have read up on this here and there a little but it's always theory, I must find time to put this into practice as it would save me a TON of time.
            PcDmis 2015.1 SP10 CAD++
            Global 7-10-7 DC800S

            Comment


            • #10
              I think it would be fairly easy to test, if you have the time.

              1) Locate the qual tool with the MASTER PROBE at A0B0 (YES moved)
              2) Calibrate your longest probe build, use A0B0, A90B-180 and A90B-90, A90B0, and A90B90 (NO hasn't moved)
              3) Move the qual tool someplace else on the table.
              4) Locate the qual tool with the MASTER PROBE at A0B0 (YES moved)
              5) Do a QUALIFICATION CHECK of the build/angles in step 2
              (extra steps, shouldn't be needed)
              6) ADD an angle to the build of STEP 2, and calibrate ONLY that angle
              7) Measure & align to the qual tool, check it with the (now) 6 angles in the probe build
              sigpic
              Originally posted by AndersI
              I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

              Comment


              • #11
                My understanding that using "Yes (DCC hits to locate tool), is going to do exact same thing as Yes (Manual hit to locate tool), one is DCC one is manual, in addition if you have DCC+DCC, it will use he 3 hits to additionally locate the tool, prior to calibration.

                B&S One
                PC-DMIS CAD v2014

                Romer Infinity

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                • #12
                  Please take a look at this paper I wrote on probe qualification using PC-DMIS. It's a little aged now, but still pertinent. The last few pages deal with moving the probe and qualifying only a few new probes. You're welcome...

                  https://drive.google.com/open?id=0B9...1Zxa1h3ME5mNm8
                  sigpic

                  James Mannes

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                  • KIRBSTER269
                    KIRBSTER269 commented
                    Editing a comment
                    Aged like a fine wine James

                • #13
                  Thank you James!

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                  • #14

                    I need your opinion how to calibrate in protect mode manually to point the sphere because the sphere is not fixed on the table and if I give the self calibration before the start of the program I do all the positions and fail to calibrate my position or two A90B90-A90B-90. thank you in advance PC -DMIS 2014
                    Last edited by sppown27; 10-26-2017, 06:43 AM.

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                    • #15
                      Originally posted by Matthew D. Hoedeman View Post
                      I think it would be fairly easy to test, if you have the time.

                      1) Locate the qual tool with the MASTER PROBE at A0B0 (YES moved)
                      2) Calibrate your longest probe build, use A0B0, A90B-180 and A90B-90, A90B0, and A90B90 (NO hasn't moved)
                      3) Move the qual tool someplace else on the table.
                      4) Locate the qual tool with the MASTER PROBE at A0B0 (YES moved)
                      5) Do a QUALIFICATION CHECK of the build/angles in step 2
                      (extra steps, shouldn't be needed)
                      6) ADD an angle to the build of STEP 2, and calibrate ONLY that angle
                      7) Measure & align to the qual tool, check it with the (now) 6 angles in the probe build
                      Works as advertised. Good stuff... On to save cal time... Thanks everyone!
                      PcDmis 2015.1 SP10 CAD++
                      Global 7-10-7 DC800S

                      Comment

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