AirBuffer for EMMS (External MMU Mount System) PRUSA Enclosure - DISCONTINUED

Update:
I made a better autoretracting system. This Airbuffer was not reliable enough. Please consider these files as obsolete/discontinued. But if you find this useful in any way or other projects you may use them anyway. That’s why these files are still online!

Every MMU needs a buffer for the filament loop which builds up when the filament is retracted for a filament change in MMU. For my External MMU Mounting System (EMMS) project for original PRUSA enclosure I  wanted a simple and minimal space occupying solution. As the PTFE tube from the MMU to the extruder is longer than usual the loop is even bigger than in conventional systems. The commercially available RMU System didn't work at all because the loops are to big and the filament gets quite amount of torque and sets the filament under unnecessary tension. The RMU was not for me.

These  “AirBuffers” uses gravity to form a clean loop. It is important to find the right weight that the filament is held unter tension but without pulling filament from the spool or out of the MMU. 

There are two different Version: 
a)  V6a is about 54g

b) V6b is about 64g

On the bottom of both there is a little groove where you can place a small weight (as used for balancing car rims (Amazon Link). 

Those little wheigts have 5g and are self adhesive.

The print file uses a trick to make the bottom heavier than the rest. In the slicer a modifier is added to the model, that makes the infill on the bottom 80% where the rest is with normal infill rate of 15%. All is used to lower the center of gravity

I tested both in different iterations for some time, but in the end I chose a spring loaded auto rewind system for my External MMU Mounting System (EMMS). So this didn't make it into the final version. But perhaps someone likes the idea or wants to use this anyway.

For each buffer you need:

• 1x 608zz bearing (Amazon link)
• Head thread inserts M3 for the CAP (Amazon link)
• optional: some small, adhesive weights (5g, 10g) used for balancing car rims for optional adding weight to the AirBuffer  (Amazon link)

I designed a LOCK that avoids that the filament comes from the shell accidentally. The LOCK swings freely as the CAP presses against the 608 bearing but is long enough that the LOCK is not compressed.
 

The latest Version had a little “roof” added, so that the wheel is not blocked if the device manages to come coals to the spool. The roof avoids the wheel being blocked by pressure against the spool.

Please show me your results and send me fotos of your makes. I like to see how you use this model. If you have ideas for improvement don’t hesitate to send them to me in the comments.   I will try to incorporate your suggestions and will modify the model for special needs if you ask me to do so. 
And of course a like ♥ or a rating ⭐ of the design are always welcome. 

happy printing, clamikra