Do you use temperature comp in your programs?

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  • Do you use temperature comp in your programs?

    We have always tried to keep the CMM rooms as close to 68 F as possible and just let the parts soak to get to room temp, then measure them. We have a customer, a major aerospace company, who is now asking us how we compensate for temperature. It's possible that our current method will be acceptable as long as we have a documented procedure for doing it.

    Just in case it's not satisfactory, I want to query the gurus out there about how they use temp comp, in case the customer wants us to use it.
    Do you let the controller check the temperature and do all the compensation, or do you type in the temperature manually?
    If you do it manually, do you type in values for the X,Y,Z axes? Do the scales grow with temperature? If they do and you only comp the part, wouldn't that cause a faulty reading?

    If you have answers to any or all of these, let me know. If you have any other considerations that we should be aware of, feel free to let me know(as if anyone here would actually hold back anything)

    Thank you in advance.
    PC-DMIS 2016.0 SP8

    Jeff

  • #2
    Be honest with you Schrock. I have never used the Comp, but would assume, (I know I shouldn't) that Hexagon uses the formulas from ANSI B89.6.2. But with size of the part varies. If you are going to get in deeper with this. I would invest in one of those LaserTemperature guns. Just because the room is at a certain temp, doesn't always mean your part is. I only say this, because if your going to be changing numbers, you want to make sure they're the right ones.
    Last edited by KIRBSTER269; 06-29-2017, 06:26 PM.
    (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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    • #3
      Originally posted by KIRBSTER269 View Post
      Be honest with you Schrock. I have never used the Comp, but would assume, (I know I shouldn't) that Hexagon uses the formulas from ANSI B89.6.2. But with size of the part varies. If you are going to get in deeper with this. I would invest in one of those LaserTemperature guns. Just because the room is at a certain temp, doesn't always mean your part is. I only say this, because if your going to be changing numbers, you want to make sure they're the right ones.
      If we do go the manual input method, we would be using a touch sensor for the part. I'm concerned about the scales because a couple of our CMMs have temp sensors on the axes and they can vary by up to 2 deg F from each other and the part. How would I know what temperature to use for them?

      Thanks for the input. I knew I could count on you for at least 1.5 cents worth.
      PC-DMIS 2016.0 SP8

      Jeff

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      • KIRBSTER269
        KIRBSTER269 commented
        Editing a comment
        Wish I could give you the whole 2 cents. I'm sure the big boys tomorrow will feel the rest of the void.

    • #4
      We do not use Temp Comp. Sorry, I will not be of service to you.

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      • KIRBSTER269
        KIRBSTER269 commented
        Editing a comment
        as always, useless bfire, you're useless. lol I'm going home so I'll see your comment tomorrow

      • bfire85
        bfire85 commented
        Editing a comment
        KIRBSTER269 So are Chief fans...

    • #5
      We use it, though it was already established when I started working here, before that I would use it but always in a controlled environment so not for long and would turn it off. The CMM, here at the new place, is located out in manufacturing floor and it's Air conditioned but not controlled or monitored like a QC lab would so maybe that's why temp controlled us justifiable... I guess.

      Dumb question: Why use temp comp in a controlled environment? If they'd ask me if I use TC I would answer....No, my machine is in a controlled environment. But then again you said it's an important costumer so I'd research just like you are.
      PcDmis 2015.1 SP10 CAD++
      Global 7-10-7 DC800S

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      • #6
        I think using or not temp comp depends on a lot of parameters.
        First, it depends on the cmm, and on scales expansion coefficient and on how there are fixed on the cmm.
        For example, on a Global, you should find in the constant.dat 3 values which defined the distance on the cmm where the scale is fixed (the expansion of the scale depends on this "zero").
        On a Zeiss, with scales at zero expansion, a part fixed on the granit will "move" compared to the scale if the temperature changes.
        In a second time, you have to check temperature variations along axes. if you have fast variations, the mean temperature can be right, but the compensation will give corrections that are not true.
        In a third time, you have to enter the xyz of origin of compensation. If you begin the prog by a comp temp function with 0,0,0, the origin is fixed at the home, far from the part.
        If you use a rotary, you can fixe the origin of compensation with rotabdata("center") assignment.

        Finally, I always use temp comp, but I'm not always sure that it's a good idea, mostly when the measurements are done during a long time...
        Don't forget that the compensation works from the controller from the moment when you started it until the controller rebooted...

        Hope this helps...

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        • #7
          Thanks for the responses. Hopefully they will be satisfied with us having a written procedure for letting the parts soak to the ambient temperature of the room.

          I feel kind of silly compensating for 1 degree Fahrenheit using a temp gage with an uncertainty of +/-.5 degrees.
          PC-DMIS 2016.0 SP8

          Jeff

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          • #8
            Originally posted by JEFMAN View Post

            Finally, I always use temp comp, but I'm not always sure that it's a good idea, mostly when the measurements are done during a long time...
            Don't forget that the compensation works from the controller from the moment when you started it until the controller rebooted...

            Hope this helps...
            How do you mean by this? like from start of the program it is 20 degrees, the program runs for 20 minutes and it is now 22 degrees but the temp comp is still working at 20 degrees?

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            • #9
              Originally posted by bigtallanddopey View Post

              How do you mean by this? like from start of the program it is 20 degrees, the program runs for 20 minutes and it is now 22 degrees but the temp comp is still working at 20 degrees?
              No, I mean that the temperature has a continuous reading, even if you start a new prog without temp comp (I was told about this by a Hex tech).

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              • #10
                Originally posted by JEFMAN View Post

                No, I mean that the temperature has a continuous reading, even if you start a new prog without temp comp (I was told about this by a Hex tech).
                Here is the most problem if the temperature has fast variations, because if the axis temperature moves, the scales compensated with a wrong value, so the length is bad !!!!!!!

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                • #11
                  In the Leitz protocol (maybe also in other ones ?), there's a setting which is called TEMPCOMPCONTINUOUS, which is used on the part sensor to compensate the temperature in continuous mode, or only on the temperature at the start (true or false).
                  I learned it yesterday !!!!!

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                  • #12
                    Don't forget that the part sensor needs some settling time when you attach it (several seconds, maybe a minute or two), before you start the program.
                    AndersI
                    SW support - Hexagon Metrology Nordic AB

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