Free Form Issues

[[Ch...]]

I'm losing my mind here and I really hope someone can help me out. This is going to be tough to explain since I can't exactly throw the customer's print on here.

I'm having trouble w/ the "Free Form Surface". If the feature - free form is utilizing the appropriate datum(s) via the recalled alignment, can I, on the characteristic - profile of a surface, click "No Datum Reference"?

Because when I actually recall on the characteristic datums A & B (what's called out on the print) the result is more than 0.2000mm. Yet, when I skew to form area and take multiple space points, I'm no where near that bad.

Is this a common issue w/ this feature? Does anyone know what I'm talking about? I know this is vague....

P.S.: I am best fitting the free form in translation and rotation. Also tried just rotation w/out translation.

[[Cl...]]

If datum's are involved you cannot use the best-fit. This is only for profile to its self.

[[Ja...]]

Surface profile needs 3 datums to give out a result. So how are you getting a result off of recalling only 2 datums (A and B)?
Assuming that without tertiary datum, you are left with one degree freedom (rotation about say Z axis) and If you are using geometry best fit(GBF) alignment such that the free form surface is best fitted to restrict that last degree of freedom (rotation about Z axis)only, then you should get proper result when using this GBF in surface profile characteristic.
If you are not getting proper result, then there might be something wrong in the reference alignment used in GBF or using best fit on cad model option.

check the plot showing actuals and nominal points, if it shows deviations such that the whole surface seems rotated or translated from its nominal then it is definitely some kind of alignment issue.

[[Ch...]]

Is it a requirement of the software to have 3 datums in order to use free form surface? The customer print only has datum-A which controls the Z depth and the level in this case...and datum-B which controls origin. There is no rotational lock. I verified w/ the customer and the two wings are not constrained w/ a rotation so that it "free form" floats into position. So I did click best fit for rotation, but not for translation. Now...if we were only using datum-A, I should be able to best fit to translation and rotation.

So my question...do I "have to" use 3 datums? Is that a quirk of the software that I'm required to use 3 datums just for this feature to function properly?

Now...just to cover my bases. I tried not using a best fit at all...and I tried best fit to rotation only. In both cases my resulting values are not logical.

I rotated to each wing and pecked it w/ several space points to see what my location deviations would be from point to point. I found that the first cavity on the gage is slightly out by this method, and the second cavity is unbelievably good. However, I am rotating to each "wing" one at a time and does not function as it should, in this case, where both wings should be involved.

[[To...]]

Please sign in to view this quote.

No. With the Free Form Surfaces option, you can use any number of datums from 0 to 3

[[Ch...]]

If you constrain the freeform feature to the appropriate datums, as you indicated via the feature alignment. Then in the feature evaluation, choose to best fit the allowed degree of freedom (example in the picture,) Then when you click "Create Alignment" you should generate a new non-zero alignment called "WP_Free Form Surface1" or some such. That alignment is what you put into the characteristic datum reference frame (as in the picture).

That's the way to constrain some degrees of freedom but not others, in Calypso.

FreeformDRF.JPGFreeform.JPG

[[Ch...]]

Hey Patrick,

That seemed to do the trick! Thank you sir!