Hollowing Out for 3D Printing

BrendtheCow

SO, I have a model I'd like to 3D print (through Shapeways), and to save on costs I'm trying to hollow it out. I can guess/check my way through it in ZBrush using Dynamesh's Create Shell feature, but I'd like something more precise where I can define wall thickness in millimeters.

For that, I'm trying to hollow it out in Autodesk Inventor (because I have access to it at work). Unfortunately, Inventor won't read .STL files from ZBrush as having volume, and therefor will not shell the object. Does anyone here have a good method/workflow for exporting from ZBrush into a format readable by Inventor? If you have a good workflow with other software I'd be interested as well!

Things I've Tried:

1. Zbrush Dynamesh Create Shell - works but is imprecise.
2. Export from ZBrush to Maya as OBJ, Export from Maya to Inventor as .step - resulted in an error on export, "Error: Failed to find translator."
3. Found the STL Importer plugin for Inventor on Autodesk's Vault(which is supposed to import STL files as files with volume). This just crashes Inventor.

Thanks

rube

I haven't looked to hard at them yet but the latest version of blender has some printing tools in it. I'm not sure if you can define a shell thickness, but you can check the thickness of your shell.

Take a look at this video (it's just a teaser of a training dvd).

[ame="http://www.youtube.com/watch?v=HolxfI4XgCE"]DVD Training: Blender for 3D Printing - YouTube[/ame]

BrendtheCow

Nice! I hadn't even considered Blender as an option. I'll play with that when I get home tonight. Thanks!

r13

I'd suggest that you might be aiming lil too precise with it. That is the 'perfect' way to do it for sure.. but...

It might be just as easy and cost similar, to build a low poly inner shell as if you were gonna pull normals from it, but instead attached it to your mesh. you will also be able to thicken some spots as well like arm and ankle joints stronger/thicker manually to make your print more durable.

BrendtheCow

The only durability concerns I really have are whether or not it will hold up to the mold making process (I print these, 2-part mold them in silicone/plaster, then resin cast them). So far the 1-2mm thick walls are holding up fine, but the material I print in can go as low as .7mm. To save as much as possible on up-front printing costs, I'm trying to get as close to that .7mm as I can.

nyx702

I printed something from Shapeways with about a 1mm thickness (in Max) and it came out WAY thinner than I expected and there were holes in the mesh. Some pieces were so fragile they crumbled in the shipping box. I wouldn't say it was their fault but in 3D space I feel like it "looks" much thicker than it really is. I should have doubled or even tripled what I thought was good enough.

If you cheap-out and the print is ruined you have to pay for another anyways. Maybe order a test of a small box with the thickness you are thinking about using. Just to be sure.

Also, I ended up filling mine with some plaster to give it more heft and strength before molding. I am not sure what you are doing but it might be a good idea to fill it with something. If you are going to do this make sure you cut your parts so that when it's glued up the filler will still run into all the parts. Doesn't have to be plaster... just what I had on hand.

EDIT: It's been awhile but Shapeways had a calculator script for Max that would tell you the approximate cost based on volume. Not sure if they have this for other programs or not. If 1 extra mm is only a couple bucks it's probably worth it.

r13

you can upload and get a cost from shapeways pretty quickly.

throttlekitty

I've spent very little time with freeware CAD software, but most of the software on the big kids table will calculate this for you. Thickness vs weight/strength/cost, etc. Maybe you'd have less of a format issue with another app?

Also, is your Zbrush mesh watertight?

BrendtheCow

nyx - I've seen other people have the same issues, but I've never experienced them myself (ordered a dozen or so prints in both Strong White and Flexible, and Strong White and Flexible Polished). Thanks for the heads-up, though A millimeter's difference in thickness on a 10"+ model, at least on the test models I've been doing (measuring thickness in Maya), tends to be a $10-20 difference. I also fill mine with plaster before molding.

ThrottleKitty - I went with Inventor simply because I have access to the software through work, but if you know of a CAD software that will let me shell an imported STL model then I'll definitely give it a shot. EDIT: And yes, it's watertight

I'm really hoping Blender does what I need it to. Judging by the preview that's going to be my best (and cheapest) solution so far.

pior

Yeah - making hollowed out model is actually way easier than what people think - especially if your source is a watertight Zbrush model.

It might be just as easy and cost similar, to build a low poly inner shell as if you were gonna pull normals from it, but instead attached it to your mesh. you will also be able to thicken some spots as well like arm and ankle joints stronger/thicker manually to make your print more durable.

That's about it really. Just duplicate your object, scale it down along its normals, relax it a few times, maybe trim out bits that are not necessary and dynamesh to whatever resolution you want. Then reverse the faces and attach that to the original. Bingo !

xrg

Blender has a modifier called solidify that can create thickness. This older CG Cookie video covers it, but doesn't cover all the new 3d print tools included in the newest Blender.

[ame="http://www.youtube.com/watch?v=ZnCf-5G7DYc"]Modeling for 3D Printing with Shapeways - YouTube[/ame]