I’ve updated the design to fix three design flaws that noticed so far:

  1. The filament guide had to be removed for Z-axis calibration
  2. The filament slid of over the filament guide at a certain print height
  3. The ball bearings were not secured well enough

2nd revision

Although this design seems to work fine during my first test print, I don’t like that the holder sits so loosly on top of the printer frame. I’ll add a clamp in the next revision.