Surface profile

[[Cl...]]

This six sided hex has a .001 surface profile callout back to -A- (center ID). If I measure the 6 planes and recall the points into FFS, I get .053" (which I know is wrong). If I evaluate each plane separately I get from .0015 - .003. The print doesn't state "all around", but I'm assuming that's what they want. Any input would be greatly appreciated.

[[Ri...]]

Are you associating the surfaces with the CAD model?

You should also evaluate the Free-Form to Datum A, and build a Best-Fit Alignment inside the Free-Form and use that as your DRF inside the Profile Characteristic.

[[Ma...]]

Perhaps they only focus on two opposing sides - in other words - maybe they are not using bits.

[[Jo...]]

I had a similar part last month
If this is for a shaft with hex drive, it would need to be all around to ensure it would fit. If evaluated individual it does not consider side angles to each other. I think what you are seeing is rotation reverting to alignment. Richards suggestion should fix that. My example is constrained, where yours is not fully constrained..

[[To...]]

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Why? I don't understand.

[[Cl...]]

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Richard, two things; 1] I was under the assumption the Best-Fit option could only be used when the profile
is to itself (no datum is involved). 2] If I'm wrong, how do your use both inside the characteristic at the same time?

[[Ri...]]

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I'm not a fan of letting Calypso attempt to perform a Best Fit inside of the Characteristic. A lot of times it doesn't work properly, you can always check by looking at the Default Printout to see if it performed a Best Fit.

I remember I had this issue many years ago, and someone guided me down this path.

Your other option would be to create a FFS from Datum A, turn on the Best Fit for it in all 6 degrees of freedom, and use that Alignment as your DRF inside the Characteristic.

[[Ri...]]

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It just depends on what you select to allow it to rotate/translate.

If you are working in the XY Plane, Datum A can only control the Rotation in the X, Y, and the Translation in the X, and Y. So in your case your FFS would be allowed to Best Fit in the Rotation in the Z, the Translation in the Z most likely has no significance in the calculation.

Once you have your Best Fit setup correctly click on the Create Alignment button. You can use that Alignment inside the Profile Characteristic.

[[To...]]

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I think your explanation is a little clearer now.

I just created a test program using Profile to A and my default printout shows Best Fit: TransZ RotZ, which is what I would expect but I do understand that on some characteristics, this is not the case.

Thanks for the tip.

[[Ri...]]

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It was Friday. I was checked out for the day.

[[Cl...]]

Thanks for the input gentleman! I think I figured out what the problem was.
I was recalling plane points into a FFS, and getting .053". Then I tried extracting
FFS from faces, my result was much more believable (.003).

[[Ri...]]

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I think this is because you weren't associating the CAD Surfaces with the FF. If you don't, it is trying to build the nominals from the actuals, and most of the time it will be incorrect.

[[Cl...]]

I was still extracting the planes from the model. How is that different?

[[Ri...]]

You were extracting the planes from the model, but when you just go to Features - Special Geometries - Free Form Surface you have not associated the CAD surfaces, so your FFS technically doesn't have nominal data.

All you need to do though, is to just select the surfaces, and it will associate them.