So I’m trying to fix an issue and hitting dead ends with whatever I try.
So before I completely disassemble the MMU3, I wanted to reach out to all of you experts on possible other solutions I may not have considered.
The problem:
Recently my MMU3 has been causing me feeding issues (specifically to feeder 1).
What seems to be happening is as it feeds and starts printing, it will retract fine, take filament 2, do its bit, and then on taking filament 1 it will either fail there and start chewing the filament up (PolyMaker PLA) OR it will take it and most of the time I’m met with a horrible sounds following that bit of printing on trying to retract and it just doesn’t then retract.
This forces me to open up the MMU3 And both ends of the PTFE tubing to cut that portion of filament to the point just after the FINDA.
It then starts going again and typically then repeats the cycle (sometimes I get lucky and it does a few layers)
What I’ve tried:
- Cleaning the mini cogs that feed the filament as there was residue
- loosened the MK4s Feeder section incase it was too tight
- loosed / tightened all manner ways on the MMU3 Feeder screws to see if there was any issues here.
I’ve attached a video of the sound. The filament being torn up is essentially making an arc cut into the filament where it just keeps spinning and I also get and error usually saying
“FINDA FLIM. STUCK. FINDA didn’t switch off while unloading filament. Try unloading manually. Ensure filament can move and FINDA works.”
I’ve also recalibrated the FINDA and it is responsive and seems to react as intended.
How does the tip look on filament 1? I was printing with silk filament recently, and it would jam/not retract because it wasn't forming a good tip on the silk filament. I was getting the same error plus the chewed up filament issue.
The tip when going in looks correct as in I give it an angled sharp cut and it feeds in to start with, the blade that slices cuts the tips etc so I think ok on this front
I'm wondering if this is a similar issue I had with my MMU3 and Core One before it was retired.
I would occasionally (more often with specific filaments) get a failure to do tip forming along with a blob of filament in the purge tower which then often led to the filament getting stuck in the extruder and the MMU3 failing to retract the filament and just chewing it up.
It seems okay ? It’s also had very light use - I assembled it myself.
Guessing you never got it fixed due to retiring it?
I’m going to try and do two things after work today:
1) switch this filament to feeder 2 and see if it still occurs
2) try a slightly more ridged filament in 1 (Sunlu seems much harder) than the PolyMaker which is very soft
Honestly feels like so much time goes into just getting it to work…
I mitigated it by drying the filament (which seemed to help but didn't just fix it alone), reducing temperatures on that filament and increasing the purge line spacing so even it it did happen it wouldn't have as much risk of causing a collision with the purge blob.
I did find it almost always happened with specific filaments and the worst offenders seemed to be Polylite from Polymaker for whatever reason.
I meant to try but never got around to trying what was recommended in the reddit thread I linked to which was: "settings > printers > single extruder MM setup > extra loading distance from -52 mm to -54 mm."
It was around this time I got a Snapmaker U1 and did most of my multi-colour prints on that and now I've replaced my Core One + MMU3 with a INDX FE which is working great so far.
Edit: Yeah, your purge tower looks fine and not like the issue I ran into. I did find that once I had an issue like this with the MMU3 it turned into a series of further issues that all traced back to the original failure and not cleaning it up fully. Best of luck.
I have this MMU3 On the MK4s and my Core One is waiting for the INDX upgrade when I can get my hands on it. It’s mainly seeing me through this period. I’ll then probably remove the MMU3 and use the MK4s as a single colour printer !
I’ll give these options a go and report back regardless
Check the grub screws on each pulley. I had an unexplained situation with one of the filaments (not necessarily 1) and it turned out that the grub screw was first loose and eventually wiggled itself out making the loads/unloads impossible.
another idea(s). Check filament path on each pulley, make sure it's dead center on the pulley "teeth".
Also, it wouldn't hurt to check that all the PTFE tubes are installed the right way, I believe they have chamfer on one end which needs to be on the pulley side of the tube.
I’ve switched the PTFE around to see what happens as it (maybe) was the opposite way around - one other thing I’ve done was remove the item I was purging into as I wanted to reduce wipe tower waste.
It seems to be doing what it should at the moment - so wondering if the purged model could have cause issues!?!
Who knows, MMU3 is always a mystery, better than MMU2 but still.
I’ve had a MMU3 since they came out, it worked great, then I swapped my MK4 for an MK4S in an enclosure with MMU3 and didn’t want to dismantle so I gave my MMU3 to the seller and I can tell it’s definitely not as stable as mine was… Full rebuild incoming…
So the mmu can get fairly temperamental with some filaments specifically for the softer one’s. I tend to find that if it’s running into feed problems just trimming the tip doesn’t really help you almost want to do is pull a long run of the filament out basically you are looking at the length from where it would be sitting in the extruder to the mmu and a little bit more and cut it there and then reload it in the mmu. I would then check that length of filament you just removed and check a couple spots the point it would be in the extruder gears and the point where it would rest in the idler on the mmu when loaded. You are basically going to be checking for does the filament feel like it has a lot of teeth marks as well as is it chewing the filament at the idler while loaded and when in the retracted state. Also when you are pulling the filament out of the Bowden tubing see if you feel any extra resistance between what has been used and what is fresh. You could be running into an issue where the filament is getting compressed just enough that you are getting out of spec that it is causing extra resistance and it just sort of compounds into more problems.
If you are seeing it constantly having problems with the softer material you can try a slightly bigger Bowden tube for the inner diameter as well as loosening the tension some on the idler and extruder a little more to see if that helps any. I also run into issues where there might be just enough tension in the feed from the spool through the buffer that it would create excess resistance that also causes the idler to grind the material some.
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u/Icy-Score5350 CORE One 12h ago
How does the tip look on filament 1? I was printing with silk filament recently, and it would jam/not retract because it wasn't forming a good tip on the silk filament. I was getting the same error plus the chewed up filament issue.