Quote Originally Posted by fred_dot_u View Post
There are no automatic programs capable of doing what you describe. The skill set required to accomplish such tasks is substantial and is part of the justification that creators have, explicitly, for charging fees for their otherwise intangible products.

For your objective, you'd do best to learn a program such as Fusion 360 (free for hobbyists) that has the capabilities to accomplish all the fine detail work such a project requires. Your wall thickness is going to be determined by the slicer, not by the model, unless it's a hollow part. Tolerances between moving parts or joined parts is very much a part of the design process. For example, my printer will allow 0.2 mm tolerance, but that represents a 0.4 mm gap between the two parts. Less high quality parts require greater gaps.

If you've been using Blender, you've experienced what I consider quite a steep learning curve, and you have my admiration. Fusion 360 has more engineering based features, but also supports sculpt-type features, as well as (for the paid version) some computer aided manufacturing features. Far more than a 3D printer operator requires, but the free hobbyist version does great in that respect.

good luck
I thought that Fusion 360 was only free for limited time. Is it free forever?