True Position MMC Callout

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  • True Position MMC Callout

    Good Morning! I am still very new to PC-DMIS and I am having trouble with the Xact measurement of a true position callout for a feature. The callout for the hole should read TP/ Ø.005 @ MMC/ A @ MMC but when I try to dimension it, it does not allow me to pick the MMC modifier for Datum A. Datum A is the plane that the hole lies on and is also my Z zero. Do I need to somehow dimension Datum A? Is there a way to add this modifier?

  • #2
    A plane is not a feature of size, and cannot have MMC. Are you sure it's not a WIDTH feature that is marked as A?
    AndersI
    SW support - Hexagon Metrology Nordic AB

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    • #3
      Are you able to provide a snippet of the dimension and Datum in question?
      Whatever a man sows, he shall reap.

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      • #4
        PC DMIS will not allow you to do something that violates the rules of GD&T. The feature control frame is invalid.

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        • #5
          I will just put the dimension less the modifier. The print must be wrong because Datum A is the plane not a width. Thank you for the help and advice!

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          • #6
            A snippet would help if allowed (ITAR/proprietary/export controlled).
            Remembering my beautiful wife Taz who's life was lost on 6-13-2020. I love you and I miss you.

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            • VVPTD
              VVPTD commented
              Editing a comment
              Unfortunately I am not allowed to post anything. I appreciate the help tho!

          • #7
            Since no one has mentioned it, I will point out that in ASME GD&T, when the M in a circle symbol appears in the DRF (Datum Reference Frame) portion of the FCF (Feature Control Frame), it is NOT MMC but rather MMB. The same applies to the L in a circle. The difference between Maximum Material Condition and Maximum Material Boundary is significant. MMC adds to the allowed tolerance. MMB allows datum shift.

            HTH & ymmv


            sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

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            • VVPTD
              VVPTD commented
              Editing a comment
              Thank you for the explanation! I did not know about MMB.

          • #8
            Widths are all the rage these days.

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