Core One + MMU3 is much too picky about the filament.
Is there a way to "condition" or prepare filament so that it feeds cleanly through the MMU3? I have this common problem at some point during a print, that the filament will jam and not feed through. This is just with single-color prints where the MMU3 is not changing filaments.
Unfortunately, I can't really tell where the jam actually occurs, but these problems only started happening after I install the MMU3, so I'm assuming it's the culprit. What would cause perfectly normal filament to just jam during a print? Most of my single-color prints fail because of this stupid MMU3.
RE:
There is a common failure mode where filament gets stuck in the nozzle and the MMU fails to unload. The MMU pulley carves a segment out of the filament, damaging it. In the next print, that damaged filament section is too thin for the Nextruder. The printer under-extrudes then stops feeding even though the Nextruder wheel is still turning. The root cause for this can be heat creep / filament residue in the nozzle's cold zone, causing the filament to get stuck in the first place.
Therefore, after issues with the MMU, check the condition of the filament in the PTFE tubes, possibly discard the first meter. Otherwise, the issues may carry over to the next print. It's less of an issue in regular operation (later, filament may wear out again from too much color changing and too little printing/purging but that's a different failure mode)
For completeness: There is an ongoing discussion on the German-language forum about oiling filaments. Can't say whether it is needed, helpful or bad, just wanted to bring up the keyword (my own preliminary findings are that it does make sense but the verdict isn't out yet). For a functional printer you shouldn't need it.
If the above filament damage is not the root cause, can you describe what "jammed" actually means? For example, when it gets entangled at the spool, my core one's extruder is strong enough to overstretch and snap ABS filament somewhere in the middle of the PTFE. It can muster a lot of force (print quality would be abysmal but the filament wouldn't "jam" in the path)
One should avoid tight bend radii by spool placement. There are 3d printable blocks that extend the five PTFE tubes into the MMU by about 2..3 cm, avoiding sharp bends. But this is more about loading than feeding.
The first thing I'd check is the condition of the Nextruder (open the idler door, clean out any debris, make sure the teeth of the Nextruder wheel aren't clogged).
And one thought: You probably rebuilt the Nextruder with the MMU-supplied plate. Is the washer on the motor shaft still where it is supposed to be? Otherwise, diffuse problems will result.
RE: Core One + MMU3 is much too picky about the filament.
Coincidentally, I've had this problem repeatedly over the last few days. Never had an issue with my Mk4S+MMU3. Not sure why it happens now with the Core+MMU3 as the extruder hasn't really changed. mnentwig gave a good analysis. For me, it seems it's some specific filaments that cause issues whereas others work just fine. Don't have the time to work out this mystery right now. I'm wondering it it has something to do with the way the filament gets fed into the extruder, which is different
Formerly known on this forum as @fuchsr -- https://foxrun3d.com/
RE: Core One + MMU3 is much too picky about the filament.
I'm beginning to wonder if my problem is really just heat creep. I dried the filament overnight and made some adjustments to the filament parameters to lower the heat. We'll see how it goes, but if it does jam again, I will do a more thorough analysis to find where the filament is actually stuck.
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Well, that didn't take long. Filament jam after just a few layers, even worse than before.
I'm not even sure it's heat creep because the heat block is only at 34°C.
I'm going to try with a different filament. The one I'm trying to print with is pretty old, and maybe filaments expire regardless as to how long you dry them.
You probably rebuilt the Nextruder with the MMU-supplied plate. Is the washer on the motor shaft still where it is supposed to be?
Do you mean this one:
RE:
Yes, that washer. It's a prime suspect as it gets lost so easily.
For a test you can reduce reduce retract speed and -length to e.g. one third of the original value. This reduces heat travelling back up with the filament.
Thermal paste may help if the heat doesn't make it out of the nozzle. Also check whether a 2 mm drill slides easily into the nozzle with its blunt end first - if not, there is filament residue.
RE: Core One + MMU3 is much too picky about the filament.
How can there be filament residue if it prints fine for 20 minutes? Sometimes it prints for an entire hour before the filament stops feeding. Wouldn't any residue cause problems within the first layer?
RE: Core One + MMU3 is much too picky about the filament.
the problem I'm describing (heat creep) happens only after maybe 1/2 hour into the print, when the "cold" zone has heated up sufficiently for filament to get stuck. But let's not jump to conclusions, let's find out first where and how the filament is getting stuck. Visible damage on the filament (other than the pulley pattern) would be one sign.
RE: Core One + MMU3 is much too picky about the filament.
Ok, I tried a new filament and the same problem occurred. Looking inside, I see the filament is damaged. I'm just going to disassemble the extruder and clean it out. I'll report back.
RE: Core One + MMU3 is much too picky about the filament.
You could also check the Nextruder idler tension screws (it was probably rebuilt with parts from the MMU)?
Usually their tension is not particularly critical but maybe something is getting stuck and the drive wheel slips.