Profile result not repeating

[[Cl...]]

Part is a cylinder fixtured horizontally facing Y+. It has 4 slots (.141 x .275) 90° apart around the OD at one end. There is a
surface profile callout of .015 to A & B for each slot. A is the main cylinder, B is the rear flat end of the cylinder. Base alignment
is A spatial Y+ and X& Z origins. B is the Y origin. Planar Z+ is the slot at the top (12:00 position) using a symmetry point.

We are doing a type 1 Gage R&R. The slot profile is not repeating. Currently I am using a secondary alignment (A spatial Y+, -
Z & X origin, B is Y origin) Any ideas as to why this is not repeating? I also tried using the A&B features themselves in the profile characteristic, but that didn't repeat either.

[[Me...]]

Are you doing a rotational Best Fit for all 4 slots to A-B?

[[Cl...]]

I am not, pleas explain?

[[Me...]]

Based on your description it appears that the slots have simultaneous requirements and should be Best Fit as a rotational pattern to -A-. No one slot takes precedence over another so they need to be checked as a pattern. This should help your results, although I don't know if it's related to your repeatability issue. Just an observation.

Robert

[[Cl...]]

I do not know how to do this best fit.

[[Cl...]]

If by best fit you mean the best fit option under evaluation?
My understanding is that this can only be used if the profile
is form only with no datum reference?

[[Da...]]

Have you looped your alignment ? Check your workholding ! Most of the time for me, it comes down to workholding. When I get desperate ,I'll put a tenth indicator on the part and touch it lightly with my finger, If it moves at all, you lose ! 🤣

[[Cl...]]

Thanks Dave. Program is looped at 3 iterations with a .0005 tolerance.
The fixture uses a magnetic v block and toe clamp, very secure.

I just added a hole in the fixture below the two vertical slots, so I can orient
the part using a gage pin that I can slide it and out. Repeats much better now.

[[Th...]]

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If this is what I think it is: you would use the "Alignment from several curves" alignment feature to establish your pattern fit from the slot features. To then evaluate relative to that alignment, I think you have to copy the features w/ point recall and set them to use that fit.

[[Cl...]]

Ok, so based on my description the slots location/orientation and Datum's A & B,
what do I tick in the way of translation and rotation options inside this option.

[[Th...]]

Actually, I might have gotten ahead of myself here. I made the assumption that these slot features were being checked as curve entities. If they aren't, my suggestion isn't really applicable.

[[Me...]]

You want to Best Fit all the slots at the same time, not 1 at a time. If you're using curves for the slots then use Thomas' advise and use "Alignment from several curves", select all the slot curves, and allow rotation around Y only. Then copy the curves used for alignment, recall the previous curve points, and check their profile using the alignment you created from the alignment curves.

You can also do this with symmetry planes and/or various other methods. The concept is the same. Measure slots with planes, create symmetry planes, create a Best Fit bore pattern of all 4 symmetry planes allowing rotation only, recall the symmetry planes into new planes, and report their position in the new alignment. Or recall the slots sides and check the profile of the slot sides in the new alignment.

Robert

[[Cl...]]

Ok, thanks. I'm using four 2d curves (1 each slot). Then recalling
those points into 4 free form surfaces. Then what about translation?

[[Th...]]

A (X/Z axes) and B (Y axis) are constraining all 3 translation axes, so there shouldn't be any translation fit allowed.

[[Me...]]

You only allow translation/rotation of unconstrained degrees of freedom. The cylinder constrains 4 DOF, the end plane 1 DOF. The only thing left is rotation around Y, which is the only thing you should choose.