So I'm using PCDMIS 2020 R1, I have a 2 cylinders that have true position and perp. call outs. This seem redundant because the primary dat is the same on both. But any way. I get a true position of .0015 then the perp is .330 on the same cylinder. Any Ideas
Cylinder true position is correct but the perp. is way out
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Consider the depth of your cylinder. If you are measuring at two levels that are very close together, the best fit algorithm can really get messed up if there is any form issue on the feature. I recently had a large diameter cylindrical feature that was very shallow, like .15” long. The part was out of round .050”. The best fit algorithm saw the shallow oval shape and best fit it by constructing the cylinder at a very severe angle. Seems kinda dumb, but that’s just how the math works out, if you cut a cylinder at an angle you will get an oval. If you measure a very shallow cylinder, the levels are so close together that it is essentially no different than measuring them at the same level, which doesn’t help to construct the true vector of the cylinder.
As Schlag suggests, more hits and more levels can help a lot. I’ll add that separating the levels as much as possible will help too. On the part I mentioned above, I had to measure a number of circles normal to the datum being compared to and constructed a 3D line between them. Then I reported the perpendicularity of the 3D line. There may be more elegant solutions, but it was what I could come up with on a time crunch.Last edited by Cris_C; 04-17-2021, 12:28 PM.
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How are you reporting this?
Legacy, Xact, GeoTol?
Perhaps you're reporting position in one location of the Cyl - i.e. Start, Axis Average or End - and it's in Position at that location but still out on the Perp?
It's times like this where Graphical Analysis can really let you know what's going on.
Applications Engineer
Hexagon UK
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in the picture datum cylinders E +D are the ones in question Dat A is the surface perp to D+E Dat B is the bottom surface dat C is the far sideAttached Files
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Looks like to me that Datum A is Parallel to D and E or am I seeing this incorrectly? Your A symbol looks like it's on the bottom surface of that picture.Last edited by KIRBSTER269; 04-19-2021, 10:12 AM.(In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)They say "Nobody's Perfect." I must be Nobody.
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Do me a favor Post your code, because what you showed in the picture looks like A is parallel to your holes, B is perpendicular, and your Trihedron isn't even corresponding to what your asking. also what is your callout. A|B|C Position and A Perpendicular?
Capture.JPGLast edited by KIRBSTER269; 04-19-2021, 10:43 AM.(In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)They say "Nobody's Perfect." I must be Nobody.
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