First and foremost, my experience doesn’t come from artwork but from modelling for 3D printing. But There are parallels.

Aside from the “normal” software you find when searching for 3D modelling software, you might want to look into the following:

For modems That are built from geometric shapes, i Used OpenSCAD a lot. It’s basically a programming language to describe 3D objects with boxes, cilinders,…

For stuff you want to digitise from a real world object, you can still find 123d from autocad on the web left and right. It creates 3D models from photographs from different angles. Great if you need a model of a tool like a hammer or knife.