Here is my attempt at designing an extruder for my Prusa i3. I took some inspiration from different designs to try to make an extruder which is easy to print, compact, easy to clean and has tight guides for the filament (to be able to use flexible materials). I made a couple of test prints with it and it seems to work fine so far. I haven't tested any challenging materials yet, just PLA. Here are the components: EDIT - Version 1.1: After a bit of testing, the grooved bearing worked fine with PLA and Nylon but not with Flexibel PolyEster so I switched to a flat 5x10x4 bearing. I improved a bit the "idler arm" to make it able to squeeze the filament a bit further and also made it slightly stronger. I was able to make a nice flexible print with this new setup. Stay tuned :-) EDIT - Version 1.2: Here is a new version. This is now designed specifically for a 5x10x4 (or 5x10x5) ball bearing and it includes an even tighter filament guide. I had some issues printing flexible polyester with the previous version, this one works better. I have also tested with PLA, Nylon and PET without problems so far. Here is a video: http://www.youtube.com/watch?v=80q71dtGmuk I have also uploaded the sources made with LibreCAD and OpenSCAD so you can customize it to your needs. Make sure you upload the remixes! :-) EDIT - Better fan duct: Here is a slightly more advanced fan duct which help distribute some airflow around the nozzle: http://www.thingiverse.com/thing:151555 EDIT - Two can fit on a 80mm carriage! Here is a video of my dual extrusion system: http://www.youtube.com/watch?v=Ca-XfL2IUWsJust drop a comment if you need me to provide some instructions on how to assemble :-)