Recalculating nominal geometry

[[Pa...]]

When recalling feature points into a point (for profile measurements), you have the tick box option "recalculate nominal geometry".
By ticking this, aren't you changing nominals to actuals? And other than if you have no CAD model, isn't this cheating?--you are telling Calypso that where it did find the points is where it should have found the points, so of course the points are where they should be. Yet I've seen experienced users use this function repeatedly. Questions:
1) When is recalculating nominal geometry appropriate?
2) And when it is appropriate, why should you have to ever do it more than once if all else with the program is correct?
3) And when you do recalculate nominals, the space point distance drops to nearly zero, but not 0.0000. Yet if you set the nominal to the actual you just measured, shouldn't space point now be exactly 0.0000?
Am I misunderstanding?
PaulS

[[No...]]

Nobody's forcing you to tick that option. It's just there to make your life easier, but you can just as well enter the correct nominals by hand.
To avoid "cheating" as far as possible, first erase all actuals, then switch to simulation mode in the CMM settings, turn off dispersion and run the plan again. That way Calypso will generate only theoretical results (actual = nominal) and the recalculated nominals should be correct.

[[To...]]

I know this might not be the answer to your question but it might help someone. The first time you "recall feature points", the "calculate nominal geometry" is ticked. Normally, you would then correct the nominal data to the numbers on your print. If you go back into "recall feature points", the box is un-ticked so that you don't change the values you previously corrected.

If I'm working from a model, I will extract the feature first, i.e. cylinder, so I get the correct nominal values, then recall feature points from circles. However, you must un-tick the "calculate nominal geometry" check box before selecting any of the circles. If you select any of the circle features before you un-tick "calculate nominal geometry", it is too late. You will need to "reset" the cylinder feature to restore the nominal values, or extract a new cylinder.

[[Cl...]]

What about recalling several 2d curves into a FFS?
If you first create the FFS, open it, recall the curve
points, then, un-check "recalculate nominal geometry"
would Calypso then use the nominal data from the
curves instead of the FFS?

[[Me...]]

I would say with profile almost never, unless you are doing it from a "Nominal part."

one thing about recall feature points that makes me nervous is that it recalls ALL the data points. this includes all filtered/ outlier data, as well as the initial points at the beginning of the scan. there needs to be a way to recall without those unwanted points.

[[De...]]

You need to un-check recalculate nominal geometry BEFORE you choose a feature / features to recall the points from.

If you have the checkbox checked then Calypso updates the nominals as soon as you choose a feature.

[[Aa...]]

Please sign in to view this quote.

This is a very important point (and very quirky software behavior--certainly not what I would have expected).

One thing to keep in mind is that the recalculate nominals default was intended for a model-less workflow. For those of us who always use models, it's a stupid default.

[[Aa...]]

Please sign in to view this quote.

I've thought this for a long time. But alas...

[[Ja...]]

Please sign in to view this quote.

So, would filtering at the theoretical level be best practice? I wasn't aware that recalling points included ALL points.

[[CA...]]

I received constantly the message --- Warning! The nominal values contradict the nominal geometry! ....But I do not what to do. I have unchecked all respect the Re-calculate Nominal Geometry...

[[Ma...]]

Perhaps it is because of user defined tolerances?

[[Ri...]]

Please sign in to view this quote.

If you "delete actual's",of the original feature then recall the points, your nominal's will be the same as the feature recalled from.