"The operation could not create a valid result" when shelling

[Anonymous]

So I don't entirely understand the shelling tool.  I'm currently working on a rather complicated part.  It's half of a cylinder with ridges cut out of the outside and the shape of a prostate cut out of the inside (I don't know how to save a part locally to attach to this, so I'd love if someone could walk me through it so I can get better help).  This leaves a lot of internal geometry with weird, thin parts.

When I try to shell from the flat face so it's 3 mm thick, it gives me the error "The operation could not create a valid result" and tells me to try changing the input geometry.  

Is this error due to the part having geometry less than 3mm thick?  Is there some workaround?  Additionally, what's with the tangency check box option?  Is that something that can make a difference in this case?

Thanks!

[innovatenate · Accepted solution]

To create a local copy of your file, use the export archive command from the main application menu.

To upload this file to a forum post, you may need to zip or compress the file first. 

The shell comand generally is used to convert solid body geometry into a thin walled solid body. It sort of excavate's the internal volume of a solid and converts it into a vessel. Any faces selected in the shell command should be remove. An easy example is to start with a solid cube. The shell command can quickly turn the solid cube into an open "crate" or "box."

Where the shell command can get tricky is with organic, "curvy" shapes. The command doesn't do well when the results "overlap" onto itself. This tends to occur when the Thickness value is too large in the shell command or the Body is too thin. You may find that you can get the shell command to work by reducing the value from 3 mm to 1 mm. You should be to find the thickness at which the shell command fails. You may be able to change the Direction of the Shell from Inside to Outside to work around the issue.

 I hope this helps. Let me know if you have any questions. If you upload the archive file, I will be happy to take a closer look.

Thanks,

[Anonymous]

I figured that was probably the problem.  It's very much a curvy organic shape.  I tried decreasing from 3mm to 0.1 mm.  Unfortunately, it still failed, with the same error.  I guess the part just has too many thin curvy parts.  Overall, being shelled isn't the end goal for us - it was just one thing we were trying to get to our /actual/ goal.  

Thanks for your help!

[innovatenate]

If your end goal is to 3D print, you may find that the MeshMixer will work just fine for that operation.

You can download Autodesk MeshMixer from the below link.

http://meshmixer.com/download.html

I hope that helps.

Cheers,

[Anonymous]

We do want to 3D print it in the end, but what we're really trying to do is "suspend" a 3D printed prostate model at a specific location in a cylinder, with slits for radiation sensitive film.  My logic was to put the prostate model in the solid tube, boolean cut the prostate out of the tube, so we could print the prostate a different color.  Then, cut it all in half, and shell the cylinder part so we can fill it with an epoxy, since we have to do 100% infill and printing the whole tube in solid infill is obnoxious.

I've only just realized that this was a crazy idea and I could get essentially the same result a lot easier by just using a pre-hollowed tube.  XP