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    I have attached a sketch from a drawing from an OEM. First I would like to know if the datum setup is legal to the new standard. If so how would you go about setting it up? I have tried to create a set with the (B) slots and a set with the (c) slots. PCDMIS tells me I cant use these features for a secondary or tertiary Datums. Until they released 2020R2 SP1 I couldn't even use the slots as Datum features. Any help would be appreciated because this is only a sample of how complex the drawing is.
    Attached Files

  • #2
    I will take a shot at this, level to your A datums, measure the B and C square slots, construct a line for B 1, 2 & 3, then construct a line between C 1 & 2. Rotate to line B and line C, origin to D. I prefer to make a sphere for the -D- just to assure it gets locked as a 3d feature. Remember to take sample hits. Also, before manually measuring all the slots, do a simple manual alignment, three points on A, measure two slots and rotate, pick one for origin. I am assuming you will be using an iterative alignment, but a 321 will work also.



    • INOAC
      INOAC commented
      Editing a comment
      Thanks for your response......I have done it this way but the results are sometimes way out there (not even close). So I'm not sure if this is getting the answer I need. I have removed some the slots and just used one for (B) and one for (C) and really get a good numbers. But this is not what it is asking.

  • #3
    You need to construct width features for B1, B2, B3, C1, C2, C3 & D and then define each set of widths as their respective datum - so B1, B2 & B3 make up datum B & C1, C2 & C3 make up datum C. You should then be able to create the geometric tolerance commands referencing those datums. The way they are depicted on the sketch indicates the orientation of the width features you need to construct. You need to measure the relevant slot sides as separate features and then use those feature to construct the widths - measure lines for 2D widths, Planes for 3D widths.
    Neil Challinor
    PC-DMIS Product Owner

    T: +44 870 446 2667 (Hexagon UK office)
    E: [email protected]


    • INOAC
      INOAC commented
      Editing a comment
      In 2020R2 SP1 is this different than creating a set from the slot measurement since it allows you to pick the length or the width? When I call the set into the geometric tolerance command It states you can not use as a secondary datum.

    • neil.challinor
      neil.challinor commented
      Editing a comment
      It allows you to report either the length or the width but I don't think there are any similar controls when assigning datums. If you create widths in the orientations shown on your sketch and then define each group of widths as their respective datums, there is no ambiguity.

  • #4
    See attached.....I tried a little experiment with a fixture just trying to set up a slot as a width. I get the same answer that is in the attached no mater how I try to set up the slot. I tried two points, two planes and two lines and got the same answer every time. So what am I doing wrong
    Attached Files


    • neil.challinor
      neil.challinor commented
      Editing a comment
      I'm guessing there might be a draft angle on those slot sides so they are not parallel. If you edit the nominal vectors so that are directly opposed then it will let you construct the widths - just remember to answer NO to update target and measured values.

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