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2020 R2 True Position Datum Callouts

Good afternoon,

For a momentary fix I have resorted to using legacy mode to get this to work for now but I really don't want to use legacy mode for 1000+ feature reporting, I'm sure you can sympathize lol

I have been tasked with writing a program that has 3 shifts (part is 136" long and machine travel is 59.750"), and when programming the middle section I have to use a theoretical for Datum E and H (because they're unreachable). I did the typical thing and created a generic feature, with comments that the operator can input actuals for X and Y locations that turn into assignments within the dimensional data for the datums, based on results from the 1st program where they could be reached.

The issue I have is when trying to dimension a feature (circle feature, true position callout to D/H/E) it will not allow me to select the datums I assigned (Datum D is a reachable Plane, Datum H and E are both theoretical's from section 1 program data) and I have to adjust the alignment and use Legacy Mode to get results.

Is there a rule against Plane/Point/Point datum schemes in R2? I used to do this same thing in R1 all the time without fail. Does the math in R2 require something more than a point for a secondary datum? Do I need to create a 2nd point offset in X from the data of datum H to make a line, and then will be allowed to use the line as the secondary datum callout?

Attaching a copy of the print

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  • That's a good solution. I was just curious. A plane/point/point wouldn't have been a good idea anyway, as your secondary datum should constrain rotation per the print, but a plane/point/point would constrain rotation using the line from secondary to tertiary.

    I was able to make the plane/point/point work in PC-DMIS though. You have to construct a cast sphere using the point and arbitrarily set the diameter. You can then use the sphere as the datum feature. Your workaround is more accurate.
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