SummaryUpdate 2/3/2016: I added a new filament spool holder where you use some 8mm threaded rod across and put into the two ends. Use the spool holder for a spool and put two 608ZZ bearing in each end to allow it to guide friction free on the smooth rod. I turned a Cubex Duo into a Reprap machine. The design files, stl files, firmware and slicer profiles are free for anybody to use if they choose to modify the Cubex Duo themselves. I've written a thorough RepRap wiki about the modifications. If you have any questions let me know. http://reprap.org/wiki/Cubex_to_RepRap_Conversion