MMU3 Cassette Compatible Buffer for Prusa Mk4 / R4 Casettes

Remix of the great, compact filament buffer by @Paul_75970 that makes it compatible with the MMU3 R4 cassettes (Version B).

Since I also wanted to use the remix of R4 cassettes, I couldn't use @mikedmor remix which squishes the cassettes, preventing smooth operation of the ribbon in the cassette.

Printed part list:

• Buffer Skirt Lower with Mounting Nuts_MMU3_Slim
• Buffer Skirt Upper_MMU3_Slim
• Frame Holder Bracket
• L Bracket
• Bottom Bracket
• Buffer Assy MMU3_Slim_R1 - Buffer Cassette Holder Top_Slim-1 from @Paul_75970
• buffer-frame-holder-narrow-hook-trimmed-1mm from @raymond_w_1165384

Hardware list:

• 4x M3x8 screw
• 2x M3x10 screw
• 5x M3x12 screw
• 4x M3x8 Rounded button head screw
• 4x M3 Square Nuts

Assembly instructions:

• Connect Upper and Lower Buffer Skirt with 4x M3x8 Rounded button head screws.
• Insert 2x M3 Square Nuts into one side of Cassette Holder Top.
• Connect Upper Buffer Skirt and Cassette Holder Top with 4x M3x12.
  
• Connect shorter arm of L Bracket and Frame Holder Bracket with 1x M3x8, skip Frame Holder Narrow for now.
  
• Connect L Bracket and Cassette Holder Top with 2x M3x8.
  
• Insert 2x M3 Square Nuts into Buffer Skirt Lower on the opposite side of the L_Bracket.
  
• Attach Frame Holder Narrow to printer frame.
  (Shift MMU to the left to make it easier)
  
• Attach Buffer Assembly to printer frame.
• Connect Frame Holder Narrow and L Bracket with 1x M3x8, and Frame Holder Bracket  with 1x M3x12.
• Insert Bottom Bracket into the right frame extrusion.
• Connect Bottom Bracket and Buffer Skirt Lower with 2x M3x10.

Connection instructions:

If you plan to connect this buffer to spools placed inside the Prusa enclosure, you can use Filament guides (and spool holders mentioned in that remix).

I also highly recommend modified Cassettes that no longer need to be removed from the buffer when loading filament.

Connect the buffer and right Filament guide with 2x 50cm PTFE tubes, and left Filament guide with 2x 85cm PTFE tubes (they will hang at the top of enclosure). You can also use 65cm PTFE from MMU3 kit, but tube bend near filament guide is quite significant then.

Then connect the buffer with MMU3 also using 5x PTFE tubes from MMU3 kit.

5th spool can be placed at the back of the enclosure on the left side (you can use Filament guide from the Cobra model), but IMO it's quite inconvenient. Instead I'm connecting the 5th cassette to external filament dryer / dryboxes.

Update info:

2024/11/18 - Recreated L Bracket, Frame Holder Bracket and added Bottom Bracket, updated instructions.

2024/11/19 - Added bracket variant for mounting buffer next to the PSU.

Moved the indentations in the buffer to closely match R4 cassettes.

Redesigned hex pattern for easier printing and reduced material usage.