True Position Repeatability

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  • True Position Repeatability

    There's a bore that I measured (offline to online) and I can only hit it 50% of the circumference due to the complexity of the part. When I get the true position of it we found it within the 0.005" call-out (actual 0.003")and we almost accepted the part as good. We used the other cmm and gave us more than the limit (0.007").

    Now we did a repeatability on both machines using 4 different angles and giving us a min/max range of up to 3 thou.

    Do you think what causing the non-repeatability problem is because I'm only hitting 50% circumference of the hole or is it a hardware problem (e.g. probehead, tp20, etc.).

    Thanks in advance guys,

    mds

    p.s.

    the cmm that's giving us out-of-spec TP is the older machine. the good result is coming from the newer cmm though the repeatability is not good.

  • #2
    Originally posted by mds_toronto
    Do you think what causing the non-repeatability problem is because I'm only hitting 50% circumference of the hole
    Yes
    <internet bumper sticker goes here>

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    • #3
      re-calibrate the probe tips, make sure both have same move, hit, speeds.
      I used to be high on life but I built up a tolerance.

      Brown & Sharpe Global Advantage
      PCDMIS CAD++ v2011mr2
      PH10MQ/SP600M


      sigpic

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      • #4
        How many points do you take? How well are the spaced out? Do you use the cylinder or circle features to evaluate?
        ***************************
        PC-DMIS/NC 2010MR3; 15 December 2010; running on 18 machine tools.
        Romer Infinite; PC-DMIS 2010 MR3; 15 December 2010.

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        • #5
          i used a circle feature using 6 hits...no initial hits...i just found out that we're using 2 different tp20 module. one cmm is medium force and the other extended...

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          • #6
            Well, as long as the calibrations of the tips came out correct, that really should NOT make a difference in the results.
            sigpic
            Originally posted by AndersI
            I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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