Along with palette(http://www.thingiverse.com/thing:118529) i made a parametric extruder based on these (http://www.thingiverse.com/thing:10783, http://www.thingiverse.com/thing:16429). It's far from finished but it can work :) i started with a simple motor base, but it can be changed with a typical Wade's or others, as the only thing it needs are 2 holes. I'm trying to use the whole system with 2 motor drivers in order to be compatible with RAMPS 1.4. https://www.youtube.com/watch?v=9fm_4CHXI-c More at http://nutbits.blogspot.gr/2013/07/multiple-cam-driven-bowden-extruder-and-the-palette.html