True Position of Feature to another Feature TP used as Datum

The ACTL's of the 70 and 40 dimensions are used to calculate the true position of the slot. Actuals are always used for calculations. If you were to calculate it off the theos, then you would be measuring it to datums ABC, not AD.

As a side note, you need to pick up all four outside edges and construct midlines for your B and C datums. You can't use one edge if it's defined as the midplane. This will change your true position values relative to datums B and C unless the sizes of datums B and C are perfectly nominal.

Offline, you run the program, and you've got a perfect world where nominals = actuals.

Real world, the actuals found by probing the part essentially replace those nominals.
You could make a print that had the actuals on it at that point.
(Deviation calculations are made by comparing the real world actuals to the perfect world nominals.)

A datum is something that is measured FROM, so, if Datum D is slightly out of position, the nominal FROM D isn't affected by that. You're measuring from wherever D is in the real world.

Hope that helps.

Thank you both of you, this helps confirm some of what I thought and clarifies others.

I think where I am getting snagged is when trying to write the program and define the nominal of the slot feature. Since it's based on the Datum D actual I would need the program to change my origin to the Datum D, then define the slot nominal, then measure the actual, then tolerance it. This device has a handful of these individual Datum D/slot relationships so my program would require bouncing around coordinates to define the slot's nominal and recalling back to the -ABC- alignment DRF.

This seemed cumbersome so I've been trying to leave it at the alignment coordinates, then the True Position function allows you to define up to 3 Datums to use as your coordinates if you don't want to use the existing DRF. The problem is if I do that the deviation values are different than just setting the coordinates to the Datum D.

First picture is the DRF set exactly to the actual position of CIR_AL2_M (Datum D) and Slot2_Pt's nominal is exactly XY 90,-230 from Datum D, and the actual has some deviation. (looks good.)
The report looks correct to me.

Second picture the DRF is still set at -ABC- coordinates, which is shown by Cir_AL2_M (Datum D) being in it's nominal position, and an actual.
The nominal of Slot2_Pt is obviously incorrect in reference to -ABC- but in correct position to the Datum D Actual.
The TP report notes the Datums used it Datum: CIR_AL2_M (It doesn't show but the value used is Actual, not the theo).
If it's Datuming off Datum D actual correctly as it's supposed to I should expect the exact same value.

Do you guys see something in the numbers (regardless of the software) that could be the problem that I don't see? If the numbers all look correct to you guys I will chalk it up to the software and move on.

Appreciate the help!

This is actually another question I have. Since Plane, Line, Line or Plane, Line, Point is slapping the top, and two edges it gets my device roughly aligned on those two edges but it doesn't define my midplanes and puts the trihedron in the corner of the part. Since Datum B and C are dimensions I can't actually make Datum B & C until I measure but I can't measure until a part is in alignment. But my part will never be in alignment until I align it to Datum B and C right? Or is just doing a manual->DCC iterative 3-2-1 close enough then you measure and then make Datum B and C from those measurements and we pretend that never happened? I feel like my cart is before the horse.