Datum as 2 planes for Perp check

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  • Datum as 2 planes for Perp check

    This is more of a general question not specific to PC-DMIS (or, in my case, Quindos).

    As can be seen in the attached image, there is a datum (Datum -A-) which is an open-ended slot composed of the two planes on the slot sides. The thru hole has a FCF for Perpendicularity to that datum. How would you go about establishing the datum reference coordinate system for the Perp. evaluation from this datum feature?

    Thanks for you input!


  • #2
    I would probe one side of Datum A with however many points you see fit. Then Copy/Paste with pattern to the other side of Datum A so I know each point is in equal and opposite locations. Create midpoints between opposing points and construct a plane for Datum A. You could either probe both holes as 1 long cylinder, probe 2 cylinders and construct a 3d line from cylinder to cylinder, or probe several circles in each and construct a 3D line or cylinder with them. I think if you want to be proper to the standard tho, you would want to construct a maximum inscribed cylinder from either scans or hit values used for the feature and then dimension perpendicularity. No coordinate system needed. If you use exact measure in PC-Dmis then you define the mid plane we constructed earlier as Datum A, then setup the DRF to match the print.
    I do not know anything about quindos, so i can't help you there, but I haven't used any software that requires a coordinate system for a perpendicular dimension. Normally this DRF would be level and origin to A, then constrain the rest of the Degrees of Freedom with the feature, in this case the feature would constrain 2 translations, and the rotation can be anything stable because this would not affect the feature measurement value.


    • derekvegeta
      derekvegeta commented
      Editing a comment
      One slight difference (only for time efficiency, especially if you intend on making a lot of points) could be Making 2 equal and opposite points and creating the midpoint, then patterning the 3 points. As long as you Name them before patterning and don't check "use default prefix" it'll be easy to select the midpoints for your constructions from the construction list (also click and drag selection from your top view would work too for construction selection).

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