here is my solid works (edrawing) files for my extruder, its not finished yet i need to add the motors but you can get the idea of how it works and please improve on it, make it printable :) three spring loaded arms apply grip to the filaments as a camshaft releases each arm at 90' intervals.more of a write up here http://minibnzreprap.blogspot.com/do what you like with it, i can supply the solid works files if anyone wants them as well..