Okay, this is not quite done, but I thought I'd throw it out there anyway.This version is less prone to cracking. Instead of a washer and nut, there is an M6 tapped hole in a piece of aluminum. But best of all, two can be bolted together to form a dual head extruder. Yes, you can have one or two of the same extruder! I'm working on a mount for this right now.See my YouTube videos of previous versions for theory of operation (http://www.youtube.com/watch?v=HMjVrmLJvIU) and how quickly the filament can be changed (http://www.youtube.com/watch?v=z_isuzpvjBc)Subversion http://svn.makerbot.com/users/charles/paxtruder/