How many pieces should I do for the next object?

4 Answers

It will be just a CAD model, it's my university project

7 parts

12 + 4 symetric=16

I'd model at least six or seven unique parts to make that assembly.
The actual number really depends on if it will remain a cad model, or if you plan to actually build one. Building a real one would benefit from having additional parts.