Improved PTFE Path for MMU Filament Changes Using (Un)Original Prusa Drybox and Prusa Enclosure

Dear all,

First of all my starting-setup: 

• MK4S with MMU3 and Enclosure

• (Un)-Original Prusa Drybox Classic (LINK)

• MMU3 5 Spools auto rewinder adapter for (un)original Prusa drybox (LINK)

• Crossbeam 20mm for MMU3 (LINK)

• Fixation for (un)original Prusa drybox on the Prusa enclosure (LINK)

I struggled with filament grinding ("Mäusezähne")

After a detailed analysis, I traced the root cause in my setup to excessive friction caused by too small bending radii of the PTFE tubes.
To solve this, I designed a new holder for 5 × PC4-M10 fittings, allowing significantly larger radii.

For that modification you need:

• 4x M3x20 (or longer)

• 4x M3x25 (or longer)

• 8x M3 ruthex inserts

• Recommended but optional: Remixed Fixation to move Drybox back (LINK)

• 5x PTFE Tubes each 1 meter long (I using 4x2, not 4x2.5mm)

• Some TPU filament 

• 6mm metal drill (yes, through the Original Prusa Enclosure) 

  • Including drill-template

Thats what you need to do:

• Empty your (Un)-Original Prusa Drybox and disassemble it from your enclosure

• Remove the 4x upper M3 screws

  

• Print both parts of the front holder for 5 × PC4-M10, assemble them into one part, and fasten them using M3×25 screws.

• Remove the 4x screws at the back:

  

• Print both parts of the back holder and fasten them using M3×20 screws.

• At this point, the assembly should look like this:

  

• Print and mount the drill template. Use a 6 mm drill to drill through the plastic and lightly scratch the metal underneath to mark the position. Remove the Drybox. Drill through the enclosure metal: 

  first with 2 mm, then with 6 mm.I used a magnet to collect most of the metal chips. Carefully deburr all holes.

  

• Even after deburring, the PTFE tubes could still be damaged by sharp edges.
  To protect them, I printed a TPU adapter and assembled it as shown:

  

The rest should be self-explanatory.
If you have any questions, please do not hesitate to contact me.

It worked very well for me. With this setup >1000 filament changes without any error and without any 2nd attempt!

Have fun :-)