true position question???

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  • true position question???

    I have alignment ABC. A is a plane, B is a cylinder, C is a line. I want to find the TP of datum B to datum A. When using legacy dimensions the result gives me the datum B 'x' and 'y' cooridinates.
    The way my alignment is set up -
    A - level Z
    C - rotate to Y plus about Z plus
    A - Z orgin
    B - X and Y orgin

    My question is, how can the coordinates for datum B in my TP callout be anything but 0,0,Z? When I just do a X,Y,Z location dimension for B the measured values are 0,0,Z. But they are not in my TP callout???

    Can anyone explain this to me?

    Thank you for any help,

    Kaleb

  • #2
    your rotation contraint is off more than likely. Try rotating from B to C then set your xy origins on B...a print or snippet of it wouldn't hurt either

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    • #3
      If you are measuring -B- as a cylinder, be sure to use more than two levels, and (when using Legacy) pay attention to the selections in the TP menu:
      - Worst
      - Average
      - Perp to Centerline
      - Use Datums
      etc.

      Each one of these modifiers (or combinations of same) can produce different results, depending.
      sigpic

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      • #4
        The x,y of Datum B will only be 0,0 if Datum B is exactly perpendicular to Datum A.

        B&S CHAMELEON/PCDMIS CAD++ V2011

        There are no bugs, only "UNDOCUMENTED ENHANCEMENTS!"

        sigpic

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        • #5
          As others have implied above, this is basically a perpendicularity requirement.
          Measure a cylinder.
          Intersect it with the -A- plane.
          This is your X and Y "zero.
          The location on the opposite end of the cylinder is where the deviation will be.
          Lately, it occurs to me
          What a long, strange trip it's been.

          2017 R1 (Offline programming)

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          • #6
            You could ask for perpendicularity of feature -B- vs -A-. You should get the result you are expecting.
            Hasta la victoria, siempre.

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            • #7
              Question on this topic: when calculating perpendicularity of cylinder to plane instead of cylinder TP to datum A, would it use same tolerance as the TP?

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              • #8
                Kind of ???? Perpendicularity would really be only orientation of the cylinder to the plane. Position would include that AND the actual location related the DATUMS. PERP wouldn't care at all if it was off 1.00 in its location.

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                • #9
                  Originally posted by Schlag View Post
                  Kind of ???? Perpendicularity would really be only orientation of the cylinder to the plane. Position would include that AND the actual location related the DATUMS. PERP wouldn't care at all if it was off 1.00 in its location.
                  True, but in this example the only datum called out is [A] which is a plane perpendicular to the cylinder being dimensioned, thus there is no location.

                  If there are more than one hole with a position call out to a plane, then it would be perpendicularity and the location between the holes as a pattern. One hole has no pattern.
                  PC-DMIS 2016.0 SP8

                  Jeff

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                  • Schlag
                    Schlag commented
                    Editing a comment
                    I guess I read the DATUM constraints a little fast

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