A simple extruder for the Smartrap uses 3 x M3 10mm screws, one M3 16mm, a 608 bearing and a M3 washer Fits on the extruder motor without modifying the base plate. Update 3 June 2014: Fixed the small gap in the motor plateuse the new round z-adapter from github https://github.com/smartfriendz/smartrap/blob/master/stl/dev/V0.4.7/zcoupler_new.st If the fillament doen't slide well through the holes, drill them out with a 2 or 3 mm wood drill, 5mm drill for the bowden tube holder.