Auto Cone extracted from a COP

We have Romer arm here with an RS3 laser on it.

I am having issues with the auto cone feature. I want to do an auto cone and then generate a circle from the auto cone, either by intersecting with an existing plane or by using the cone feature under construct a circle and create a circle at a given height.

If I take individual auto points and construct a cone, I get the results that I expect. I have been doing it this way for a couple of years now. Recently I tried to incorporate the auto cone feature into my programs and I can not get smart as to what is going on with this command.

Ex. Part I am currently working on, if I construct a cone from individual points and intersect that cone with a plane or construct a cone at a given height I get the result that I am looking for....in this case a circle with a diameter of 7.194"( verified with a caliper ). Now if I extract the same cone via the auto cone command and intersect this new cone with the same plane as above, I get a result of 7.394" and if I construct a cone at a given height( same height as the above mentioned plane ) I get a result of 6.560"

Has anyone else experienced weird result like this?

I have contacted tech support twice on this subject and have yet to get any kind of straight answer on this?

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AndersI over 8 years ago

I was reading your clicking comment as something you did when it was time to select features for intersecting the cone and the plane. If you had had two cones at the same place, then it would have been possible that you selected different cones when clicking on the different ends.

As for the original problem, I agree with you - the intersection with a plane should be in the same place if the differently constructed/measured cones really are exactly equal. but depending on how the points are collected, if the cone is constructed or measured directly, if the probe compensations of the measuring points are used as from the original vector/surface points ( BF) or re-computed ( BFRE) using the surface normal of the computed cone, all of this may make a difference, especially if you're using vector points, but also a surface point may well have a vector different from the same point calculated from the actual cone.

Normally the differences are very small, but as a draft angle doesn't make for 'nice' cones (vertex very far away, if I understand it correctly), the sensitivity even to small measuring errors can be quite large. Also, the draft angle may not be present in the cad model, giving PC-DMIS the wrong theoretical surface normals.
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AndersI over 8 years ago

I was reading your clicking comment as something you did when it was time to select features for intersecting the cone and the plane. If you had had two cones at the same place, then it would have been possible that you selected different cones when clicking on the different ends.

As for the original problem, I agree with you - the intersection with a plane should be in the same place if the differently constructed/measured cones really are exactly equal. but depending on how the points are collected, if the cone is constructed or measured directly, if the probe compensations of the measuring points are used as from the original vector/surface points ( BF) or re-computed ( BFRE) using the surface normal of the computed cone, all of this may make a difference, especially if you're using vector points, but also a surface point may well have a vector different from the same point calculated from the actual cone.

Normally the differences are very small, but as a draft angle doesn't make for 'nice' cones (vertex very far away, if I understand it correctly), the sensitivity even to small measuring errors can be quite large. Also, the draft angle may not be present in the cad model, giving PC-DMIS the wrong theoretical surface normals.
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