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Unfold Surfaces Error

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We've discovered that the Unfold Surfaces Tool fails at a crucial point in a sculpture we are fabricating for an artist here.

I've included two .vwx files. "3 turn spiral A.vwx" is the one we fabricated from. The other file, "spiral mmy 01b.vwx" is another attempt with the same geometric result (unbuildable).

The red unfolded surface in "3 turn spiral A.vwx" is the one that pulls away from the structure about half-way up, though the other two surfaces seem to be fine.

Attached you'll see two photographs ("unfold error 1.JPG" and "unfold error 2.JPG") from a complete set of documents showing the entire process, in which we attempt to fabricate a small-scale mock-up for 30' tall sculpture. Our complete documentation set shows exactly where the part failed, and we can send it if it will help.

The last photo ("spiral fabbed.jpg") shows a completed spiral in which the piece that failed was re-fabricated by hand (tedious and difficult even for our crew). The final, full-scale piece cannot tolerate even minute irregularities, however, and building it at full scale would be too risky, so we have not yet taken the project all the way to completion.

Any assistance or insight would be very welcome!

Has anyone else had any experience with the Unfold Surfaces tool like this?

Edited by mmyoung
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I don't have VW09sp4 so can't access your files.

But the project looks like a wonderful challenge !

Since your errors appear after the first pi rotation , my gut tells me that you

may have a common resolution issue involving the compounding of trig. rounding errors.

Possible solutions :

1) Program to maximum decimal accuracy.

2) Use radians.

3) Set-up 'key frames' via Working Planes at the specified 180? (3.141592654r ) rotations to check the rotational accuracy.

4) It may be possible to segment the curves into shorter lengths.. then add the curved surfaces in the unfolding.

Thnx for sharing ...

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Islandmon, thank you. I was hoping you would look at this.

Great suggestions, of course! We will examine it again in light of these, and I'll re-post when we find out how this works it out.

Do you have time to take a look at it if I backsave it to ... (I forgot what version you like)?

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Yes .. that is what I do ....

although 100mm seems a fully rounded special case ... that number could just as easily be 100.0012345678 ... but you would never know it unless the units were set to read more than two decimal places.

Now that may not be a big deal for those who do not require closure... but I like

my theoretical models to be as close to perfect as possible when I zoom to the limit.

Try setting Units to 0.00 then mess around with a few object placements using the both manual placement and the OIP to fix the points.

Now reset the Units to 0.0000000000 and see what you have wrought ... you may be surprised.

Now duplicate each object and rotate around the XY and Z axis ... small errors begin to compound into significant displacements.

All i'm saying is that with compound rotational displacements in 3D space it is essential to check the math prior to each iteration. That is ... if you want to avoid compounding the small XYZ misalignments between the parts.

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