I posted a query about this in my introduction which was probably not appropriate . Can an object being prepared for 3d printing be constructed from a number of smaller 'sub-objects'? For example if I wanted to model a rivet on a surface could the rivet be a separate 'watertight' sphere and intersect the surface ( of equally watertight geometry)? If so then is there a good guideline for the amount one object should intersect another? Many Thanks.