Another Buffer Design... maybe?  

Another Buffer Design... maybe?

Hi all,

I wanted to show you my pre-design for a buffer setup. I kind of fell into a creativity low, maybe you have ideas how to make it better and discuss it.

For the system I attached a Check-Valve (Filament Check Valve von Yannik) to the spoolholder. Therefore the filament can't get pushed back into the spool. I then attached about 80 cm PTFE-tubing (2,5 mm inner diameter/4 mm outer) to the check valve which reaches all the way to the MMU3. But I didn't attache the tube to the MMU3. I attached another short piece of PTFE-Tube to the MMU3 and then a fitting to attache a bigger PEN Tube (4,5/6mm). The PEN-Tube is 60cm long. I was then able to thread the long PTFE-Tube into the PEN tube.

Now it is easy to load filament because the two PTFE Tubes are almost touching. I just need to make sure, that the long PTFE is pushed all the way inside the PEN, which isn't difficult.
For unloading I just need to release the Check-Valve and pull the Filament. 

When the MMU3 does a filament change, it trys to push back the filament. But because of the Check-Valve, it pushes the PTFE Tube out of the PEN tube, to extend the path from the check-Valve to the MMU3. 
When the MMU3 loads Filament, it first pulls the PTFE Tube back into the PEN tube. When the two PTFE-tubes are touching again, it pulls filament from the spool. 

Now my problems are:

• The pushed out PTFE tubing hangs loosely. I am afraid, that it gets tangled with the other tubes. Is there a way to somehow guide the tube which gets pushed out of the other tube?
  I only printed short prints yet, I will update as soon as I printed a long print with lots of filament changes.
• It works that way, but when I switch the attachement of the tubes (big 4,5/6 tube attached to the check valve) it does not work. When the mmu3 loads Filament, it immediately takes filament from the spool, without pushing the ptfe tube into the other tube. I am not quite sure why that is...maybe because of friction? Is there a way to force the behaviour I need without relying on magic =P

Here are a video and some pictures of the setup:

Btw: This is my first forum topic ever made. I hope I described everything well.