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angularity of a constructed 3D plane

slipper57
I have to construct a center plane between two planes and I get it, that I have to click on dist and construct a 3D plane, then call that my datum (we'll call that datum B) . After I construct the 3D plane, I have an Angularity call out, to the top of the part (we'll call that datum A). I have a MAX Material on the angularity call out also. (Dimensionally from the two planes) . My issue is.... on the CMM print out, its giving me the 'bonus', the correct width for the bonus, but its telling me that the angularity is OUT of tolerance by .100 plus?

Same with the other direct... that I construct dat C and the angularity call out is from A and B datums. Datum C is constructed the same way as datum B... 3D dist.

ALSO... when I look at my "actuals" / hits on the CMM... I do not see how these angularity call out can be OUT .100.

Any help will be appreciated! I'm sure I am missing something simple. Thanks
  • I haven't needed to report an angularity like this before, but I think you could create a width two planes and report the anularity of the width and apply the MMC to it.
  • Maybe construct the mid plane from mid points. A constructed mid plane is a perfect plane, so without real boundaries that would used to calculate the angularity. Just a thought.
  • Engineers would have saved everybody's time if they just required perpendicularity instead. In that case I would have dumped this part on the comparator & use precision square for each side. Or used tiny ball on the height gauge & swipe as much as possible that 1/4" thickness. I learned over the years not to kill yourself over dumb engineering ideas coming from folks who had spent 1 semester or less in school doing GD&T.
  • in reply to JEFMAN
    This would be my method.
    Make the mid points from the points you measured on each plane.
    Construct the plane from the points.

    Other softwares would allow this and do it, but they are using what the software THINKS would be points if they were actually measured, so is that better? Who knows.
    Easier, absolutely.
    Better (equally accurate)? Ehh. Guess it depends on the programmers writing the software package and how close to true form the real planes are.
  • Maybe construct the mid plane from mid points. A constructed mid plane is a perfect plane, so without real boundaries that would used to calculate the angularity. Just a thought.

    Is this indeed a thing? I always though planes have no boundaries no matter how they are constructed... Is there a document we could reference to see how pcdmis handles constructed features (such a as planes) and what to expect from situations like the one you advised?


  • Is this indeed a thing? I always though planes have no boundaries no matter how they are constructed... Is there a document we could reference to see how pcdmis handles constructed features (such a as planes) and what to expect from situations like the one you advised?

    A mid plane is constructed from 2 planes, as an "average plane" (average of centroid coordinates and ±average(abs(vectors)), so you can't dimension the flatness, for example (nor the angularity) because there're no hits inside.
    When a feature is constructed from intersection or projection, it's constructed from perfect associated features, and not from hits, so you can't dimension the form, only the size (example : circle on a cone at a height).
    If you construct from hits, the plane has its own limits in terms of dimensionning, but the associated plane has no boundaries (you can intersect it with another feature wherever you want, even if it's out of the cmm !)
    It's really clear in my brain, maybe not in my text...Disappointed


  • A mid plane is constructed from 2 planes, as an "average plane" (average of centroid coordinates and ±average(abs(vectors)), so you can't dimension the flatness, for example (nor the angularity) because there're no hits inside.
    When a feature is constructed from intersection or projection, it's constructed from perfect associated features, and not from hits, so you can't dimension the form, only the size (example : circle on a cone at a height).
    If you construct from hits, the plane has its own limits in terms of dimensionning, but the associated plane has no boundaries (you can intersect it with another feature wherever you want, even if it's out of the cmm !)
    It's really clear in my brain, maybe not in my text...Disappointed

    Yes now I follow you, it is more clear :P
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