True Position screw/nut then DATUM E

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  • True Position screw/nut then DATUM E

    Hello everyone, it's my first message on this forum and I'm Italian so sorry for writing mistakes!
    I use dmis pc portable v.2020 R2 with romer 8325-7 arm, I work in metrology for an automotive sector company, but I have doubts regarding the true position of a hole with respect to a screw or nut.
    I usually use iterative alignment for DATUM A B C, where usually A are 3 specific points of a plane, B a hole and C a slot.
    More and more frequently the Client drawings foresee other screws and nuts, where for example a screw is a datum (datum E) and the other nuts / screws have a true position of 0.4 respect datum E.
    In this case I found out there are 3 ways:
    1. Use the "position between" function for dimension by selecting the output of datum E and of the screw to be checked;
    2. Remove the legacy dimension flag and use the ASME method, then create the reference E and then the output of the screw with respect to E;
    3. Set new alignment where you choose the screw / datum E as X / Y / Z origin and then resolve the outputs with respect to E before calling the alignment to drawing.

    All three methods give different values, in particular method 3 is the most restrictive. Which of the three methods listed is the most correct?

    Thanks for the help, good job!

  • #2
    Any chance you can post a snippet of the drawing/callout (so we can see the feature control frame and datums)?
    PC-DMIS CAD++ 2o19 R1 SP11


    • #3
      how to calaculate 3d vector


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