Prusa i3 filament spool axle holder

This is a holder that can be used to create a very simple spool roller, using a threaded 8 mm rod and some nuts, washers and bearings (as included in some Prusa kits, like the ones from Semi-Utilitronic Industries). It is designed to fit an aluminum frame (6 mm), but you can easily adapt it for other frames, the OpenSCAD file is included.

Update: There is one disadvantage with this spool holder, because the filament will drag along the threads of the spool axle rod. I have not found this to c