Circular Runout on a Sphere

I was recently shown a drawing that called for Total Runout of a section of a sphere. Since this is not possible per the Standard, I recommended Circular Runout instead. However, I found out that PC-DMIS does not allow spheres for this control.

When I use a cone as an input feature, PC-DMIS allows it but doesn’t allow circles constructed ON the cone.

I read in the Help files that only circles with “surface data” can be considered as valid circle features for Circular Runout: an example of this would be a circle constructed on a Cylinder, but not a Cone or Sphere.

So, I have 2 questions:

Is Hexagon considering support for using a Sphere feature for Circular Runout?
What would be the best workaround for evaluating Circular Runout on a specific section of a Cone (or Sphere). Ideally, I’d be looking for multiple results for cross sections of my choosing.

Rob Jensen neil.challinor

Caemgen over 1 year ago

Measure a series of circles rather than a cone or sphere.

I'd measure the sphere first, zero it, and then take circles at different planes outputting the runout from those, if I had to do this and had enough sphere arc-length to pull it off.
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bfire85 over 1 year ago

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Trevor McLaughlin over 1 year ago

Seems like probing a series of circles on the sphere is the best option here, like Caemgen suggested. I was focusing more on constructing circles ON the sphere but PC-DMIS won't let me use those in the Circular Runout dimension.
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Schlag over 1 year ago

You probably need to pull the hit point data from the " sphere " other wise its looking at a single value ?
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JEFMAN over 1 year ago

Seems like probing a series of circles on the sphere is the best option here, like Caemgen suggested. I was focusing more on constructing circles ON the sphere but PC-DMIS won't let me use those in the Circular Runout dimension.

The intersection of a sphere and a plane is a perfect circle, because it's the intersction of the perfect sphere constructed on the hits ansd a plane.

In this case, I would construct cicles very close frrom each other, two by two, then construct segment between hits (same number of hits per circle), and the intersect lines with generic planes and construct circle.

Using the code below at #1 should work also in your case :

https://www.pcdmisforum.com/forum/pc-dmis-enterprise-metrology-software/pc-dmis-for-cmms/414743-constructing-a-circle-from-a-cone-and-dimensionning-the-circularity
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KatmandudaMeow over 1 year ago in reply to Caemgen

you would need to calculate the IJK and/or vector approach if you did this though correct?
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KatmandudaMeow over 1 year ago in reply to Trevor McLaughlin

can you dimension it as a profile "FORM ONLY" in legacy?
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Matthew D. Hoedeman over 1 year ago in reply to Caemgen

well, no. You would need to if you were going to do a profile-type dimension, and it wouldn't be circles as a circle will only ever measure in a plane.
But for runout (which is a circular result) a series for circles on the sphere would tell you if it were running out. That being said, if your machine has a lot of drift in it, it wouldn't give you very good results, the machine needs to stay at the same singular axis (one axis MUST stay the same) to get good results. If you were doing circles in the Z plane, the machine needs to stay at the same Z value for all the hits.
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Trevor McLaughlin over 1 year ago

I was hoping to be able to construct a "Sphere" circle using the measured sphere as the input feature, but I can't get it to work. It gives me a "math error." However, even if I could get the construction to work, I'm doubtful that PC-DMIS would let me use it.
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R2ah1ze1l over 1 year ago

If you were to pierce your measured sphere data with lines to construct points, you can take the created points and construct them into circles. Then your circle would have 'point data' to enable using the runout. Not sure how well that would work for you, but it works for me when needing runout of a diameter on a cone surface as opposed to if you intersect cone with a plane which always results in '0' for a reported runout value on the circle created.
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