RE: Core One MMU3 Filament unloading getting stuck
Same problem here with different types of filament, but especially with PLA. I have the Core One kit, with the MMU in the side panel, and therefore a custom set of PTFE tube lengths.
I already tested a lot of different things to solve the issue and it drives me crazy.
The interesting thing is, that the unloading problem occurs nearly every time when doing prints without color changes and thus when the final unload happens -- but on multi-color prints, the unloading issue didn't happen (for small test prints). I suppose that whenever a color change occurs, my slicer settings for ramming and the cooling moves, etc., take care and form nice tips. However, the final unload did not use those settings; at least, I didn't find the ramming or unloading stage in the generated gcode, so this might be done by the printer itself.
Another thing I noticed is, that when using the HF nozzle, the printer cools down the nozzle before unloading the filament, which is not done when using the default nozzle --- but that cooling is also done during a color change (tbh I don't remember if I used the HF nozzle when observing this during the color change).
Finally, when the filament is unloaded, I can hear the filament tip vibrating as the gear teeth move against it, since the Nextruder gears are still spinning when the MMU takes over and pulls the filament. Not sure if the setting for this is the unloading distance in the slicer...
Things I tried:
- reducing overall nozzle temperature
- tested everything on both HF and default nozzle
- playing around with the ramming and cooling moves (but again, I think those have no effect for the final unload)
- creating a custom filament profile (on the printer) with lower temperatures than e.g. the default 215C for PLA
- tested the HF profile when the default nozzle is installed (to get that nozzle cooling before unload) -- which at least gave me a less stringy tip
- dried my PLA for 12h at 40C
- played around with the settings for the length of the PTFE tube (from far to short to a bit too long)
- tested different retract speeds
RE: Core One MMU3 Filament unloading getting stuck
I too started with MK4S and then added the MMU3 about two years ago. Multi prints worked very well with almost no problems. Except for TPU, which I realize is not supported. But even with TPU I managed some prints with dozens of PLA/TPU changes.
Since the MMU3 changes were made to the Nextruder, I forgot that the filament sensor is triggered when the idler wheels move away from the drive gear. So I recalibrated the filament sensor making sure it was pulled into the drive gear and that the idler moved outward.
Ran 4 hour stress test with 250 changes in 4 colors and no problems.
I'm running a buffer box with the MMU on a rail and custom-length tube running through a Y-splitter so I can still use the side spool if I want.
Y-splitter
Swing arm clips
MMU mounting rail and port
I tried getting a feed tube length by inserting filament from the MMU end of the bowden tube to the Nextruder, marking the filament and then measuring. This resulted in a length that was too long because the MMU tried to drive the filament into the Nextruder while grinding a dent in the filament (made a bad noise!). So I backed off 10mm at a time until the MMU didn't grind the filament on loading. On unloading, as another post stated, I can hear the Nextruder drive gear click against the end of the filament about 5 times. Although I don't like it, the stress test went well.
RE: Core One MMU3 Filament unloading getting stuck
Hello!
I have the exact same problem as @VladimirD. The filament unload fails because the tip is bent. It happens almost always with the same filament (position 4 of the MMU3), but not always. The fault occurs in the Nextruder, so the fact that it always fails with the filament I have in position 4 of the MMU3 seems rather coincidental to me... But I'm mentioning it anyway, just in case. Has anyone found a solution or improvement for this specific problem?
Photo of @VladimirD
RE: Core One MMU3 Filament unloading getting stuck
I am having a problem where the filament is getting stuck in the nextruder above the gear and below the Fitting M5-4 where the PFTE is held. If I unscrew the fitting and pull up manually the filament comes free without too much force. The resistance seems to be just enough that the MMU3 cannot unload the filament.
I have cleaned out path and blown it out with canned air. I disassembled the nextruder and can't see anything obvious that is causing the filament to stick.
what am I missing?
Same thing happened with me and I tried (I thought everything) until someone asked me if I reassembled the Nextruder's idler arm and filament sensor with the same parts that were provided to me from the original MMU3 kit (I originally purchased the MMU3 for a MK4S, than when I got the Core One I purchased the MMU3 Conversion kit to turn my MK4S back to stock, while adjusting the MMU3 to retrofit the Core One. I inadvertently skipped the step of removing the filament sensor from the original stock Nextruder and replacing it with the MMU3 variety.
Making the Core One ready for the MMU3 also requires changing out the Main Plate with an alternative fitting one.