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archturn

Trouble with helix spiral command

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I'm having trouble creating the helix need to use as a subtract from my stair baluster. The profile I am trying to "spin" always has the wrong orientation to the helix. Any help would be appreciated. drawing is attached.

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This is a very interesting problem.

Just to see if I understand, is the attached picture more or less what you are trying to draw?

mk

Edited by michaelk

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I'm pretty sure I did it the wrong way. :D

Something is happening with the nurbs curve underlying the helix that I don't understand. I'm hoping that someone will step forward with an explanation.

When used as a path for an EAP it sometimes does a repeating pattern of one big turn and two small turns.

If the profile is small enough, it behaves as you would expect...

But extracting the curve back from one of those EAPs yields a nurbs curve with the same issues....

So I gave up with the helix and used a sweep.

I'll post the file so you can see how I did it. It's not perfect. There is a slight seam. That may be because I was sloppy making the profile, but I suspect that it's a limitation of the method I used.

I'm hopeful that someone with a better understanding of nurbs curves will offer a better solution.

mk

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Thanks for your help. I'm with you until step 6 - extract all surfaces stitch and trim. Not sure what you did there

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Sorry!

3D Tool set. - Extract Tool > Surface Mode > Prefs > Selected All Entities selected.

Select the sweep and hit the green checkmark.

That gives you a group of 55 surfaces.

Ungroup.

With all the surfaces selected Model > 3D Power Pack > Stitch and Trim Surfaces

This gives you 2 generic solids. One is the one you want. The other looks like the original profile. Throw that one away.

This whole step is because I wasn't able to subtract solid or split the sweep object. It's a "cheat" that turns the sweep into just a surface and then creates a solid out of those surfaces.

Let me know if that doesn't make sense.

mk

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I don't know if it makes sense or not. I'm a little in no man's land. I'm so accustomed to sweeps to get what I want because they are never tapered like this one. I've never used the 3D toolset like this so I'm not sure what I am doing. I guess it is like an intersect command?

I get an error message: "surfaces could not be trimmed as they do not intersect to create a closed volume"

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What did you use as the starting object for the helix-spiral?

mk

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The primary issue is that it's laying in the xy plane.

Select All

Rotate 3d 90? about x to bring into standing

In Front View

Select the Spiral & the Profile

Extrude along path selecting the options to Lock Profile Plane (relative to xy) and Fix profile (relative to the path normal)

Select both the EAP and the main geometry

Subtract

you also need to tidy the profile a little as it doesn't marry exactly

[img:left]http://techboard.vectorworks.net/ubbthreads.php?ubb=download&Number=7002&filename=Liquorice.png[/img]

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mikaelk

When I tried to used the helix spiral I used a vertical line. When I tried to replicate what you did I did not use the helix spiral but the sweep.

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Brian

Nice catch. I never noticed that the lock was only xy instead of relative to the current view....

I'd still like to know what's going on with that nurbs curve. If you try to EAP an interior profile you can sometimes get the one big loop, two small loop pattern.

Archturn, if you're still trying to do my very convoluted process, you may have created the extract with the wrong preferences and mode settings. (That would get the error you experienced.) Make sure when you extract you are in the Extract Sufraces Mode (4th mode) and the Extract Preferences are set with only Select All Entities checked.

Post back or send a PM if you get stuck.

mk

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BCD

I did rotate as you suggested - Makes sense but I am still having issues with the EAP. As Michaelk has said you get strange results. I get 1 large loop, 1 small, 1 large, 2 small then 3 large. The EAP command is possessed.

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