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.
RE: MMU3 does not load enough filament to MK4S Nextruder
I tried the custom G-code. I assume it goes in the "Color Change G-code" box between the m600 and the G1 lines. If not, please let me know where better to put it. It vibrated for a while, but still did not load to the nozzle.
RE: MMU3 does not load enough filament to MK4S Nextruder
Would this be a calibration from the menu "Filament Sensor Calibration" with the filament plumbed through the MMU3? OR what else would this entail. Re-calibrating from the menu with MMU3 did not seem to make a difference.
RE: MMU3 does not load enough filament to MK4S Nextruder
The filament calibration of the Nextruder is what I am talking about. On my system (6.1.3) the filament calibration is under control, Calibration and Tests, Filament sensor calibration. See step 8 https://help.prusa3d.com/guide/6-preflight-check_754328 You just use a piece of filament fed in by hand.
RE: MMU3 does not load enough filament to MK4S Nextruder
There is also a menu option: Control, Loading test. To test the loading of filament from the MMU. https://help.prusa3d.com/guide/11-first-flight_357309
RE: MMU3 does not load enough filament to MK4S Nextruder
if there is a rattling noise then the filament is all down. There must be some mechanical missalignment.
RE: MMU3 does not load enough filament to MK4S Nextruder
Can you confirm the extruder is upgraded using these steps: https://help.prusa3d.com/guide/9a-mk4-s-nextruder-mod_683106
This upgrade completely changes the filament sensor behavior, more specifically the standard filament sensor is located at the top of the extruder and it detects inserted filament before it contacts the drive gear. Whilst the MMU version detects filament when the idler is pushed to the side when filament is inserted between the drive gear and the idler, as a result the drive gear is able to grab the filament.
RE: MMU3 does not load enough filament to MK4S Nextruder
Great question. I don't know. I built it from the kit provided. How do you tell modded parts from "older" non-modded parts? What should I look for?
RE: MMU3 does not load enough filament to MK4S Nextruder
Because of problems with TPU (flex filament) I rebuild the original sensor on the nextruder (steel ball design) and inserted following G-Code:
M708 A0x0b X25 ; extra load distancein
to the custom G-code of the printer settings.
RE: MMU3 does not load enough filament to MK4S Nextruder
Can you confirm the extruder is upgraded using these steps: https://help.prusa3d.com/guide/9a-mk4-s-nextruder-mod_683106
This upgrade completely changes the filament sensor behavior, more specifically the standard filament sensor is located at the top of the extruder and it detects inserted filament before it contacts the drive gear. Whilst the MMU version detects filament when the idler is pushed to the side when filament is inserted between the drive gear and the idler, as a result the drive gear is able to grab the filament.
I had to look through all the spare and extra parts. I found a bag for the upgrade to the MMU that was not applied. Thank you! That made quite a change. I wish it was more apparent from the instructions which version of the parts is which. The MMU upgrade has extra hexagons on the parts.
Now rather than loading successfully less than 1 in 10 times, it now seems about 50/50. Often (now) when it does load, the head starts to print. The filament seems to get stuck and throws an error. The system tries to unload. This leads to Stuck FINDA errors.
I'm not sure if these new issues are extruder or MMU or both. But at least it is a step forward.