Adding Datum Mobility Makes Results Worse

[[Ia...]]

Maybe I'm going crazy, but I don't understand this at all. I'm trying to better understand curve and freeform, so I was playing around with an inspection program and ran across this.

[[Cl...]]

I'm no expert on this, but Calypso is shifting the datums around for MMC, skewing the result.
Does changing their evaluation help? Not even sure if you can change their evaluation?

Have you tried a secondary alignment in place of the 3 individual datums? You won't be able to
use the MMC, but would be curious to see the difference, if any?

[[Ia...]]

I was actually doing an experiment on using alignments vs inputting features as datums. Then I was curious how adding some datum mobility would effect results. Didn't expect this. You would think it would shift the datums around for the optimal results, not make them worse.

Changing the evaluations of the datums only modifies the results by a tenth or 2.

[[Ia...]]

I just noticed that when you add MMC, "Iterations" appears on the top of the characteristic template. Help file says

"If you select the MMC/LMC option, the feature will be fit into the tolerance band. Under Iterations, enter the desired maximum number of iterations for the best fit. With "in Tol", calculation is continued until all actual points are with the tolerance circles."

Anyone ever use this?

[[Me...]]

Ian,

In the first example where the datum features are referenced at RFS, the tertiary datum is being ignored. If you look at the default printout, you should see where a Best Fit has occurred around the datum axis established by the secondary datum. You can also right click the curve feature within the line profile characteristic to see the BestFit axis.

This is a bug that needs to be corrected by Zeiss. You will not noticed this behavior when circles are used as the datum references.