MMU3 does not load enough filament to MK4S Nextruder
I posting out of desperation here.
I have a brand new MK4S (assembled from a kit). It prints great! It is easy to load filament by hand. The Nextruder grabs the filament just great.
If I use the MMU3 (assembled from a kit), it will load filament right up to the Nextruder, then seems to fall short. The gears can't seem to grab it. When I open the idler, I can see that the filament is just 1 or 2 mm beyond the beak. It seems to not be enough for the gears to physically grab. Only maybe one in seven filament changes will it successfully grab the incoming filament. It seems to stop too early. Like it should keep feeding for another 5 mm or so to really let the gear grab it well.
This does not seem to be a filament head shape or bend issue. I've tried all the troubleshooting I can think of. I have adjusted the tension screws all over. Flush, protruding, sunken. No changes seem to work.
Is there a setting in the slicer to specify more 5 more mm of feed? I've even tried cutting the Bowden tube shorter, it still won't grab. As far as I can tell, the filament sensor is correct. Every time I calibrate, it lights up or turns off correctly.
There seem to be some troubleshooting columns that talk about earlier version of the MMU and recompiling firmware values. Although I have several years experience with 3D printing, this is my first Prusa. I don't think I'm ready to try that yet. Not to mention, a lot of the troubleshooting and remedies out on the net are for older models. There seems to be very little helpful information for a MK4S/MMU3 combination. Most "filament feed" searches that come up for the MMU3, seem to be MMU3 specific issues with stuck filaments and filaments not getting through the MMU3 mechanism, not for this particular issue with the Nextruder failing to grab the filament.
Any ideas or help out there? I would love to say that the MMU3 is as easy as the MK4S. It just prints and does it well. But so far it has been a headache.
Thank you in advance,
Formidable Dice
RE:
You can add a G-code command in the custom G-code section of the printer:
M708 A0x0b X25 ; extra load distance
X25 works for me (old sensor design on the nextruder with the steel ball). If it's too much you will hear a cracing sound.
RE:
Are you using the MMU3 mainplate, Idler and sensor setup for the nextruder? If not, the sensor may stop it short of the gears.
You may need to recalibrate the filament sensor if using the MMU3 Nextruder parts.