Flex filament tangles around extruder gears
Dear all,
I am fully aware that this is no new issue, tangling flexi filament (NinjaFlex TPU in my case) is a known problem and there are tons of topics available already. But before you strike my topic as such, hear me out because I was unable to find an answer to my problem.
I am struggling with this issue for a few days now and I found out that the tangle only happens at a very specific moment in the printers' preparation sequence to a print. It is apparent that the tangle happens at the moment the pressure in the hotend is built up, right before it lays the double line on the front side of the build plate. You see and hear the idler-gear-latch-thingy shake wildly and after that nothing comes out of the nozzle: the filament has tangled. I think what happens is: the extruder gears keep pushing the filament inwards while the pressure in the hotend becomes bigger so it gets harder to push more filament in. At a certain moment right above the hotend the filament flexes into a direction it shouldn't, rather than entering the hotend. The flexiness of the filament causes the filament to take the path of the least resistance.
The same happens when I use the "load to nozzle" function and pressing "No" when it asks me if the color came out right so it keeps extruding. Here, it takes a little longer before the filament tangles around the gears, I guess that's due to the slower feedrate of the extruder gears and thus the slower build-up of pressure inside the hotend.
If my guess is right, that the problem is due to the (too-) high pressure in the hot-end, I must admit I have no clue how to fix it ... Would anyone willing to help me on this issue? Your help would be very much appreciated!
My setup:
- Prusa MK3S + MMU2S.
- All requirements to print flex filament were taken into account.