Hey Adam, not a FB employee but I have thought about doing this, I don’t see why it’s not possible. I would recommend ABS over PLA for obvious strength reasons and so you dont need to modify the CAD files and surrounding components to allow for building a thicker plate. Obviously plastic won’t be as strong as aluminium but I think you would get away with ABS if you had a good enough printer.
I think some of the plates could be 3D printed without compromising the system too much. Others, if made of plastic, would probably be too flimsy and either bend, break, or you would lose way too much precision and get other problems.
Off the top of my head I imagine these would be fine to print:
Z-axis motor mount, with added gussets
Peripheral mount plate/Vacuum pump mount plate (we’re making these out of plastic in all kits going forward)
Cable guides (we have a new plastic version of this legacy part)
Track end and joining plates (only for indoor installations not subject to direct sun)
I wouldn’t recommend printing the cross-slide plate, wheel plates, or gantry corner brackets without adding possibly significant ribs/additional material to the design.