Unfolding Nurbs Surface Using 3D power pack bug

[Douglas McDermott]

I wanted to see if this is me or a bug.

I am having trouble with the unfold surface function in the 3d power pack. It seems that I may have found a limit to its ability to unfold a surface with a large amount of penetrations thru it.

To explain:

My project requires a cylindrical ring with a 5" radius that is 2" tall and 1/4" thick. This ring is to have rectangular penetrations of 1" tall by .30" every 5.37˚ from center. (It would look similar to a hose clamp with the worm drive screw that catches the slots in the strap.)

I first create a cylinder of 5" a radius and 2" height using the cylinder tool. I then create a second cylinder of 4.75" radius and 2" height inside and subtract the small from the large to create the ring.

I then create the penetration rectangles of .30" x 1" placing the first in its proper location I use the duplicate array /circular array tool to distribute at the 5.37˚ using the center of the ring as the pivot point. Then selecting them use the subtract solids function to create the penetrations.

Simple and no problems up to this point now.

The real problem comes from the amount of these penetrations.

If I try to create 40 duplicates of the rectangle and subtract them from the ring it works and visible looks correct but when I then extract the outer surface to a nurbs surface and try to unfold using the unfold tool it it gives me the error describing that it is not a developable nurbs surface and cannot be unfolded.

At first I thought I had made some mistake in how I made the nurb surface but here is what is bothering me . If I reduce the amount of penetrations to about 16 it works fine. I can extract the surface and then use the unfold surface just fine. It gives me the flat surface I need to send to the waterjet machine.

Anyone have any thoughts?

Thanks

[Benson Shaw]

The unfold may not function as you wish, possibly a bug for the reasons you discovered. Go ahead and submit as a bug even though VW2010 will not likely receive further updates. If it's not a bug, you loose a bit of time in sending it. If it is a bug, VW2011 development may resolve it.

My suggestion:

For now, the whole thing can be drawn on a 2d rectangle without the 3d model. Send this 2d drawing to the waterjet.

After the cutting, that's gonna take some fancy forge or mandrel work to bend 1/4" material into a 2" cylinder! Is it metal? Plastic? Or maybe just get a cylinder and mill it instead of the waterjet? Hope it all goes well.

-B

[islandmon]

Did you try duplicating the CylinderObject, then converting it to a Generic Solid prior to unfolding ?

Also, if 3D modeling is essential , then consider creating only a single 1/40 ( 9? ) arc segment containing the rectangular penetration.

Unfold it ... then duplicate > add surface , as required, on the plan.

When working with repetitive 3D shapes, reduction to the lowest common element is often beneficial.

[bcd]

Good advice Islandmon

[Douglas McDermott]

Thanks For the advise. I will submit the bug and try both methods suggested. Just to practice I have been working fully in 3d for any of my companies industrial design / fabrication work for about two years and still feel very novice.

The cylinder is actually a 10" diameter with a 2" height and 1/4" wall thickness. The fabricators are a company that does old school iron working and art. they have been working to bring in new methods of fabrication to old school smithing practices. Like laser cutting repetitive shapes and then bending and forging together Here is a link to there site: http://www.redstarironworks.com/

thanks all

[Benson Shaw]

NIce parts & beautiful products!

And I see now, it's 5" radius, not 2" My bad.

-B