This is a proof of concept for creating a fully 3d printed PCB using a dual extrusion setup with ABS for the board and a conductive material (such as wire glue, conductive paint, copper clay, etc..) for the traces. This would of course require a paste extruder for the conductive material.
I haven't tested this yet, but it should work. There are a few variables on the top of the scad file for customization (width of the traces, width of the pads, thickness of the conductive material and board thickness).
If we're able to 3d print a PCB with working traces, then there wouldn't be any need for etching a copper board.
This design is based on the Gen7 opto-endstop design : http://reprap.org/wiki/Gen7_Endstop_1.3.1 and I used the OptoEndstop.pcb file from github (https://github.com/Traumflug/Generation_7_Electronics) for the holes/traces positions.
If this works, then maybe the whole gen7 electronics can be converted : http://reprap.org/wiki/Generation_7_Electronics
A tool for automatic conversion of .pcb files into .scad would be required because doing it by hand is very time consuming.
If someone is able to test this and confirm whether or not it works, then that would be great!