Filament Jam when unloading (it's not the common ones, i guess)
Hello everyone,
i had the MMU2s since about 6 Weeks and could already print a couple of Models successfully, but about 2 days ago, it started to fail at the end of the single-filament print when it tries to retract the filament and get stuck in the Tube when the MMU2s unit tries to pull it back from the Hotend.
As you can see on the Pictures here, the Tip looks awful but i couldn't find any guide (neither KB articles or Forum, or even google) which tells me what to do when the Filament tip looks like X.
i have already tried the followings:
- Unclog nozzle by cold pull and pushing the needle through
- raise the temperature during print by ~5°C
- adjusted the Extruder Gear tension in several ways but it's not getting better
- Make sure it's not the mmu2s unit itself by manually loading and unloading the Extruder -> same issue
Can someone help me with this?
RE: Filament Jam when unloading (it's not the common ones, i guess)
After countless hours of bugfixing and trial and error, i found the issue.
As unlikely as it sounds, it was heat creep. The thermal paste of the cooler block has worn off and caused the filament to not cool fast enough during retraction and unloading, that caused the gears to squish the still soft filament into this shape and hence block and jam in the tube.
RE: Filament Jam when unloading (it's not the common ones, i guess)
Update:
The heat creep was only a part of this issue. I found out that it is mainly the pressure and backpressure of the feeding tubes to the mmu2s unit at the back. If they are too high, the filament will be pushed against the gears in the hotend while it retracts, that causes the still soft filament to be deformed.
I now got rid of all tubes feeding the mmu2s unit and just plugged in 5 cm of tubes to get the last few cm into the mmu2s.
RE: Filament Jam when unloading (it's not the common ones, i guess)
@pecadis
That's very interesting. I'm having this problem as well but primarily with Aquasys 120 soluble filament. The filament itself is fairly rigid and I could see this increasing the friction in the tubes on eject the more tube there is between it and the spool.
I've spent a good portion of the day to day trying to get the soluble filament to reliably load and unload during a print. This gives me some ideas on experimenting, thanks!