My original problem was lack of space for my Mk2S and MMU2S so I had to come up with a wall mount bracket solution https://www.thingiverse.com/thing:3157502 I used this for a while with a flat filament buffer of the type Prusa eventually started to supply with the MMU2S but I was unhappy with it. Loading and unloading the filament was a major faff.
Then I found Graham Law's Prusa MMU2 filament rewind guide https://www.thingiverse.com/thing:3690758 and I redesigned that to suit my space available and my existing wall brackets. All kudos to Graham for the original brilliant idea, which involves using a spool as buffer for each individual filament
My solution is definitely over-engineered and some of the design choices were dictated by my existing brackets and the holes I already had in my wall.
I designed my own printable buffer spools and filament guides, and reworked Graham's PTFE bracket to suit.
Each filament feeds off the back of the roll, down through the fixed guide and then takes three turns around its spool before entering its own PTFE tube.
As filament feeds it tightens around the spool which then turns in tandem with the main filament spool. When the MMU2 pushes the filament back this loosens the three loops around the buffer spool so stops the main spool going slack. The buffer spools are designed to the correct size to retain the amount of filament that pushes back, three loops are sufficient for this and I have yet to have a single tangle. See the main image, in that filaments one and two have been unloaded by the MMU and the loops you can see are the maximum that gets pushed back on each.
This solution is so much easier and quicker to load and unload than a flat panel filament buffer, and the simplified filament path considerably reduces the friction in the system.
The main brackets accommodate 105mm wide filament reels, and there is an optional spool and drilling guide provided if you wish to make this narrower to allow up to 95mm wide reels.
6 x Filament Rack
5 x Filament Spool
5 x Filament Spool Minus 10 (Optional)
1 x Filament Rack Drilling Guide
1 x Filament Rack Drilling Guide Minus 10 (Optional)
1 x Filament Guide Strap Left
1 x Filament Guide Strap Right
3 x Filament Guide Strap Centre
5 x Filament Guide Strap Hoop
1 x Filament Guide Strap Brkt Set
5 x PTFE Filament Guide
5 x Buffer Spool Brkt Endcap
5 x Buffer Spool Bracket
3 x Buffer Spool Wall Brkt Centre
1 x Buffer Spool Wall Brkt Left
1 x Buffer Spool Wall Brkt Right
10 x Spool Half
5 x Spool Hub
30 x M3 x 10 Stainless Skt Csk Screw (6 per spool)
25 x M3 x 10 Stainless Skt Cap Screw
20 x M3 Stainless Nut
Wall Fixing Screws and Plugs as Required