Hi there,
This is Bogdan from Romania.
I'm a mechanical engineer - specialized in the industrial robotic field, 3D designer, industrial designer and, 3D modeler.
For some of my projects, I'm also doing the physical prototype too.
I'm doing product design, industrial design, reverse engineering, ideation, etc.
I have over 15 years of experience working on various systems/devices across multiple industries, from concept to launch.
1 - in order to have all the parts fitting together will be necessary to design a jointing system with keying for each part and a method to secure the part in place
2 - this will involve working with an editable file - stl files are not suitable for parametric editing... :(
3 - instead of fdm printing (as you required info about the filament type) i will advise you to make it sls/sla even in powder or resin (- upon getting in touch I could show you parts printed in all technologies), this way making much better for the presentation/exhibiting, and also for post production processing - sanding, painting, etc
I don't have my own printer (I had a cube pro duo, but throw away as is much easier and convenient to work with a 3d printing house), so I could have your model/parts printed in several locations, with different materials, etc, which I consider to be more convenient :)
For any more questions, we could chat here, including the whole details of the project, final price, time frame, deliverables, etc, etc...
Regards
Bogdan