Prusa i3 MK3 (MK2S) filament runner for external spool

thingiverse

I'm not a fan of cantilevering a big heavy spool off the top of the printer frame, so I go outboard. This is for use with external spool holders. I recommend: https://www.thingiverse.com/thing:1471454 Print two of these and sandwich a 608 bearing between. Insert it in the hex hole at the top of the Z axis. Just slide filament through the angled slot and get friction-free feed. 12/23/17: You can get tight printing with Z greater than 180mm, so I added a lift piece you can stack underneath the runner. You can add this even with a print going on. 'F' marks the front. I also tweaked the runner to make it smoother. 1/27/18: I added a version with slightly wider clearance to account for bearing manufacturing variability if you encounter rubbing. I added a pic of a good reason to go outboard.