Need clarity with Profile setups not using Free Form

[[Si...]]

Hi,
Having issues with Profile with 2020 Calypso, well mostly always have had this issue.

The Drawing feature would be Surface Profile .025mm I A I

Characteristic setup would be the Surface, then I would enter Datum A for Prime, Second and tertiary Datums as I never can data produced until all 3 are used.

Surface
A
A
A

Is what the window would look like for the set up.

Is this correct? How should I be doing profiles sine I do not have Freeform/Curve. We are doing a repeatability test using a Ground bar that is less than .0001" flat. We get a repeatable flat call out but for the Profile it jumps from .00055" to .00069" range. This range is apparently unacceptable as we have a tolerance of .0002 for the Finished product. The engineers want to rule out any CMM irregularities.

The setup of the two surfaces we are doing the Profiles against are ( your gonna laugh ) Surface 1 top of the ground bar, Surface 2 is the CMM Granite ( I was against this ) .

So how should I set up the characteristic with out free form , then how would I do it with free form as we may move forward with purchasing this.

[[Ja...]]

one way to set up (without freeform) would be to use geometry best fit alignment.
Create a geometry bestfit alignment using the concerned feature and allow for best fit for DOFs not constrained by datum -A- (meaning check mark for all DOF not constrained by datum -A-).
Use this alignment in your profile characteristic.

[[Si...]]

SO If i have two Rails, and one rail is called out to be Profile .025 to the other rail which lets say is -A-, I would do a Geo Best fit for -A- and in the eval, would UNCHECK the Z and rotation of Z ?

The rails are both at the same height, think of it like they are a set of train tracks running parallel with each other.

[[Ja...]]

so you have two rails A and B. You want surface profile of rail B wrt rail A as your datum.
In the above window,
1) In the alignment dropdown window, choose any alignment that uses rail A in its definition to constrain any and all DOF it can. (if your base alignment uses rail A, then no need to change this otherwise you need to create a secondary alignment and use that here)
2)Use select elements button to select rail B feature. (Because you want to best fit rail B feature around datum rail A)
3) In evaluation constraints, it is asking you which DOFs you want to relax so as to bestfit rail B feature (check boxes for these DOFs). So if datum A is constraining translation in Z and rotation in Z, those boxes should be unchecked.

( In my earlier comment I might have explained it incorrectly)

[[Si...]]

Ok, makes sense now. Ya last comment had them to be the other way around when being checked or unchecked. Ill try this out and see how my results come out now.

Thanks a lot.