MMU buffer filament catcher and Prusa bearing improvements

Original MMU buffer parts are quite good, but in my setup the filament tends to droop and get caught on things so I figured that a simpe arch would fix the problem. Well it does with filaments that don't have much internal tensions, but with those that have tensions it doesn't help at all. So as a bit of a hotfix I created and snap-on sidewall which seems to keep the filament loop in check.

The new base part has two updates: first is that the PTFE tube holes are restricted so cannot slip out from base. I had this happening with a filament roll that was bit hard to pull from and the PTFE tube got sucked in too deep.

The other change is an somewhat experimental addition that allows you to wind the filament twice around the wheel (enclosure for the wheel bottom). This kinda works but due to the filament aligment the loops rub on each other so might not be optimal.

Also tweaked the Prusa bearing parts a bit because I wanted to have the wheel centered and roll without wobble.

The catcher attaches to the original base with zipties so it works with old base also. The walls snap in the catcher. Might be bit tight…

OpenSCAD source: https://github.com/spegelius/3DModels/blob/master/MMU_buffer_remix/MMU_buffer_remix.scad

• added a ‘catcher’ for the buffered filament
• finetuning the Prusa bearing parts: centered spacer, tighter bearing axle parts