How to add thickness to a mesh making sure it's manifold and good for 3D printing

Question

I'm using blender to prepare a cosplay armor from a 3D model I have. The first part is to cut the model into pieces (e.g. a chest piece). Now this piece is just a "curved surface" (the original model is a solid object, I need to make a "shell" out of it).

To print the surface, I add some thickness to it. The problem is that adding thickness (using Add Modifier > Solidify) results in a mesh that has thickness, but is not good for 3D printing - it's non-manifold.

Here's a simple example. Consider this curved surface:

(Normals show that everything is facing the right direction)

If I add some thickness, it seems fine:

But if you look at the generated mesh, it's messy: Note how most of the "bends" are fine, but to upper right bend just bends into itself with some faces crossing other faces.

Another example: consider this shape: (the cylinder part has a radius of 1m)

If I add 0.75m thickness to it, it's fine:

But if I want 1.5m of thickness: I would hope real solidify would close the cylinder part completely. Instead there's a negative inner cylinder within the outer cylinder. Needless to say, this can't be printed, you can't apply boolean modifiers to it, etc.

I can fix these issues using Blender's great 3D tools (I'm using Blender 3.0.0), but this requires a lot of work (Some of the meshes are quite detailed).

Is there a better way to add thickness?

Thanks.

Answer 1

The solidify modifier is fairly simple, and does not perceive the part as a whole. This scenario is very common in 3-D. You can somewhat overcome this problem by using the Remesh modifier after the solidify modifier, But you might lose some detail, and you will lose all UV mapping. Maybe that is not a problem for you.

Answer 2

You may want to use the 3D printing tool box add-on Here's a video showing you how to use it.

https://www.youtube.com/watch?v=0rgrLWFUjlk