True Position of Angled Cylinders

[[Za...]]

Hello all, it's been a while since my last post, but I was wondering if anyone has any suggestions on what would be the best way to calculate the True Position callout of the angled cylinders for Balloon #5. I have it setup already, but I'm having a hard time believing that the results are accurate.

For -C-, I've tried using each spot face scan as its own datum and also recalling both spot faces into a plane and using that as -C-.
For -D-, I've tried using the Chamfer (Cone) and the Thread (Cylinder) and the results are similar.

I'm rotating the TP to the angle and the trihedron looks like it's pointing in the correct direction. I'm not using any secondary alignments either.

[[Jo...]]

The C-D Alignment doesn't fully constrain the location of the holes. You could try making a geometry best fit alignment with C and D and restricting degrees of freedom as needed.

[[Za...]]

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Thank you for the response Jon, would you be able to explain that in a little more detail? I've never had to use the geometry best fit alignment feature before.

[[Ro...]]

when dealing with Cylinder TP's i just intersect the cylinder with a plane to crate a point (Circle) and let the cad model set my nominals X & Y.
I was told by someone at Zeiss to do it this way, even if the cylinder is not angled..

[[Ri...]]

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You're missing out on the Angularity of the Cylinder Axis though.

There are (3) options for evaluating Position of a tilted axis:

1) Perform all of the necessary Translations/Rotations to move/rotate the coordinate system to make it normal to the feature axis (and to help match the up the Basic Dimensions).

2) Switch your Shape of Zone to Polar. This will make it where now your Projected Tolerance Zone is normal to the Cylinder Axis. The biggest drawback to this is the nominals won't make a lot of sense, so if your drawing doesn't match the CAD, then there will be error in your results.

3) Use Calypso 2023 and the new GD&T Position. It will automatically make the Projected Tolerance Zone normal to the Cylinder Axis. The drawback to this is the same as option 2.

I would not suggest intersecting your Cylinder Axis with a Plane to create a Point unless your drawing shows that (the automotive world does this a lot).