BlendShell is now released. It makes the job of creating 3D printable models easier. The models are strong, cost less and print quickly. BlendShell is free and open sourced.
Youtube intro:
Download:
Comments and feedback is most welcome.
Edit: New video showing the latest updates and a better tutorial.
A very welcome and useful add-on, thank you very much for developing and sharing. 
I’ve installed and tried it. Some first feedback:
As soon as you change the Size parameter, the Seed is created. It’s a bit confusing that there’s a Create Seed button underneath those values, making you doubt if the Size parameter only shows a preview and the Create Seed button still needs to be pressed, or if what you see is already the seed. Maybe it’s more logical to put the Create Seed button at the top of the panel.
The default Min. Thickness value is set to 3.50. Most users will do their first tests in a default scene with generic Blender units, and will then not see any shell being created, because the thickness is very high.
I’ve created a test scene with a manifold version of Suzanne (using Voxel Remesh). When I:
— create a Seed,
— decrease the Size value to make it fit inside Suzanne,
— set the Min. Thickness to a value like 0.01,
— select Suzanne and press the Create Shell button,
— the process explodes and makes Blender crash.
I’ve attached the scene. If you want me to do more tests and discuss the add-on, please feel free to send me a private message. I’m very interested.
Thanks!
BlendShell test.zip (4.4 MB)
@Metin_Seven
Thanks for the feedback. Those are good suggestions.
I checked your file. Perhaps you forgot to set the Step size. Since your thickness is only 0.01, the first step (default 0.1) will expand the seed beyond the model, and then it cannot be stopped for 600 steps. So setting iterations to 50 or 100 should be safe while experimenting.
I could get a shell, with a thickness of 0.1, so please try it and let me know.
Also try the addon with the supplied blend file (dog model), that model works with default settings. From there you can play with settings. That model is like 100mm in real life, which I thought would be a more practical size to test.
There is a write up on github page that explains the settings and what could go wrong.
Thanks Aniket!
I’ll experiment some more.
Hi Aniket,
I’ve experimented some more, setting the units for my Suzanne test scene to millimeters, scaling Suzanne to about 20 cm height and applying the scale.
My main issue is the lack of value reference. When setting the scene to millimeters, the value fields don’t indicate the unit next to the value. Is the default 3.5 Min Thickness value expressed in millimeters?
For example, if I use these settings on my Suzanne test scene, only a very slight change is visible when I execute Create Shell:
I’m trying to avoid using your sample scene so far, because the add-on should be usable without having to study the sample scene.
I’ve attached the updated millimeter-based Suzanne scene. Maybe you can provide some pointers which values are effective?
Thanks!
BlendShell test.zip (4.4 MB)
Hi again Aniket,
I’ve checked out the sample scene. A few remarks:
When you change the Seed size after having moved it, it resets to the scene origin. It’d be great if you could change Seed parameters without resetting the location.
The default values work fine here.
When I try to drill a hole with 32 sides in the Cylinder, I get this error:
Here’s a screenshot of the hole object and settings:
Edit: I forget to select the dog first, my bad! 
Stupid me, I forgot to select the dog first! 
BlendShell test mod 011.blend.zip (4.7 MB)
Hi !
Those are blender units. (Probably I should display them in mm etc)
I guess you need to also set the unit scale to 0.001 if you wish to use mm as units.
When I did that the model was 0.2 mm in height, which obviously confused the addon. Because the min thickness is limited to 0.5 mm only, there is no room for it to expand. (Probably I need to fix it)
I worked on your model, set the unit scale and made it 200mm tall. With shown parameters got a very pretty shell.
The file is attached.
I know it is a bit tricky and that is why I had to include a sample model with everything set correctly. But now I am working on an update to show units etc.
Edit: However it took 6 mins to finish. 
Great !
Thanks again for testing, yes it needs some fixes. Its only version 0.1. Working on it !
Thanks Aniket!
You’re working on a fine add-on, please keep us posted!
Thank you. it’s very promissing
A new update is available. (same link as above, but get the version 0.3.0)
What’s new:
1 - Object picker (No need to select the model all the time)
2 - Values are displayed in units
3 - Delete drills option
4 - Info panel to display dimensions, volume and units (Don’t forget to set your units and unit scale in blender)
5 - Some bug fixes and improvements (fixed exploding seed)
This should fix many issues as kindly pointed out by @Metin_Seven and other users. Thanks for the useful suggestions and let me know if it can be improved further.
Working on a new video, probably with more info and less explosions. 
Great, thanks! I’m going to check it out as soon as I get home.
Hi Aniket,
I’ve installed the latest version. Really nice improvements!
The Seed object doesn’t reset its position when the values are altered. 
I like the Target picker. This solves forgetting to select the mesh.
And I love the info section, very useful.
Keep up the good work!
Happy to hear that the fixes are working well.
Updated the top post with a link to a new video showing the latest updates and a better tutorial.
Hi Aniket,
Nice explanatory video, thank you.
A few questions:
Could the default Drill count maybe be changed to 1?
I’ve personally never used more than one escape hole in 3D prints.
When you drill a hole in a vertex-painted model (like the dog model in the video), the sides of the holes get random vertex paint specks.
Would it be possible to derive the hole sides as well as the inside surface from the average vertex paint values at the outside vertices of the hole(s).
In that way, if you drill a hole in a model’s black area, the hole sides and the inner surface will get black vertex paint as well.
It’s not really clear to me why there is a Seed Divisions and a Max Triangle Area value. Both affect the polygon density. Why not keep only one of the two?
Thanks!
Hi,
Yes you can change all defaults. Drill count is on line number 506. I am attaching a mod version here, you will need to remove the old one and install this one.blendshell-031.py (18.4 KB)
The vertex paint feature seems to be beyond me right now. Same with fixing the UVs of drilled area. But I will try if possible. As a workaround you can vertex paint the drills as black (or any other color), that will probably work.
In some cases, like small cavities, the seed will stop expanding before it gets a chance to divide the polys. So we end up with a low poly shell. If you start will more divisions this won’t happen.
Great, thanks!
