RE: Keep getting a filament stuck message on my MK4S
Hello,
Make sure the nozzle is very clean. This was the root to my problem I believe.
Kevin W. Ray
RE:
Update - I’ve done several multi hour prints of smaller pieces and they have gone fine. But a Gridfinity bin sets the alert every time. A couple were likely correct because the print had warped. But even those without (visible) warping caused the stuck filament error to appear. This tells me that the detection of stuck filament is quite sensitive. I turned the detection off and the prints completed successfully.
I’d be curious to know the logic behind the detection and if it can be adjusted.
RE: Keep getting a filament stuck message on my MK4S
I've had those issues too and disabled the Stuck Filament dcetection. I also have the issues like in this post. Also almost all of the prints i print with the HF 0.4 Profile (and of course the HF 0.4 Nozzle) have very very poor layer adhesion, in Prusament PETG, Amazon PETG and all of my rolls of PLA.. I am also Really unhappy with this upgrade.
RE: Keep getting a filament stuck message on my MK4S
Running into the same issue, so upsetting. Prusa support thinks that it's a filament sensor issue.
RE: Keep getting a filament stuck message on my MK4S
I have had similar issues. I have the MK4 kit, which I bought soon after it came out. I have an aftermarket enclosure, and it has ran almost flawlessly. Recently, I bought and installed the MMU3, and now I, too, am receiving the "Filament Stuck" error on a lot of prints, and after thinking about it, it's always on full-bed prints. Height does not matter, as it usually happens almost immediately.
In my case, however, it is actually causing bed shift, and it is scrapping my parts. I figured there was too much tension on the PTFE tube, so I selected a different buffer system, that would use less tension between my spools and the MMU3. Started printing parts last night, single color, using PETG, with the buffer overridden--I had the spool on my old spool holder, with the PTFE tube jury-rigged to hold it right in front of the spool.
Started the print and went to bed. Just got up, and it had jammed after a few layers, but had shifted even prior to the error.
I am very disappointed. I've been wanting the MMU for years, and finally was able to get it, and now I have gone from printing non-stop, to not being able to print anything.
I'm pretty sure it's something in the MMU3, not the printer proper, at least in my case, as it was not an issue before. I'm sure it'll be solved after some back-and-forth support, but it's still frustrating.
RE: Keep getting a filament stuck message on my MK4S
Hmm , as part of installing the MMU did you change anything on the print head? I have literally identical symptoms but have not fitted the MMU3 yet nor had I played with the tubes. I simply fitted the 4s upgrade. Did you touch the gear box?
Chris
RE: Keep getting a filament stuck message on my MK4S
I have only done what the instructions require. I checked to make sure the metal (or plastic) space was there, as you do remove the planetary gears to install the MMU3. I followed all instructions to the letter, I've assembled 8 Prusa printers all far, so I have a basic unstated of what to do.
Last night I decided to try my print again. I'm printing a different buffer system, as the stock one isn't working very well with my confinement. I do not believe it's the main issue, but when removing filament, it took more strength than I wanted, so I want to streamline it as much a possible.
I turned my printer on, and had it extrude filament via controls, as it had crashed from "stuck filament" the night before. I let it do its thing for a minute, then stopped and told it to reprint the last print.
Side note: I noticed filament was going into the extruder with nourishes gear marks on it randomly. I loosened the MMU3 about a quarter turn, and will see if that helps any.
I went to start the print, and it crashed immediately, talking about finda sensor jam, so I went to unload, and that errored. Tried to physically withdraw the filament, nope. I removed the planetary gears, and the plastic housing with the o-ring, still stuck solid. With the gears removed I was able to push the filament in, rather than out, and I found this: 
I clipped it, carefully put everything back together, via the installation instructions, and reloaded the filament. (Side note: this is Duramic 3D PETG, my go-to for years. I've tried numerous brands, and Duramic remains to be the only one I've been able to print through my 3 printers with no hitches, other than some of the more expensive brands.) I restarted the print and went to bed. It's 0830, and it's chugging along, with no shifts so far. It is a 16hr print, so I will see how it goes.
I really don't want to be one of those people saying "I should have bought the Bambu with the AMS", as I'm a Prusa brand pusher; I've gotten at least 4 other people/companies to buy a Prusa. I'm trying to get a XL at my current employer. But the MMU3 is being very frustrating. It will do great for a while, then it'll shift and crash. I'm sure it just needs some more tweaking to the correct tension here and there, but most people don't want to deal with that.
RE: Keep getting a filament stuck message on my MK4S
Update:
Haven't had the issue after thoroughly cleaning the nozzle (heated to 285c, pushed a lot of white pla through until no black specks of PCCF appeared, then pushed some more through to be sure). I've completed multiple 12+ hour prints without issue.
Never had to clean a nozzle to that extent before but it appears to have fixed my problem.
RE:
I'm having a similar problem. I wrote a whole essay about my mk4s setup and experience but the website decided to say nope and failed to submit my comment after the page reloaded so I'll just say the question part:
Is turning off stuck filament detection safe? I feel like that might solve the problem but like someone else said, what if it actually does get stuck? I've had the error 4 times in a row but the last time it actually was stuck and I had to adjust the feeder tension (I loosened it thinking I would help something but made it worse). I'm also near the end of a spool (Galaxy Black pla) and I printed a gaurd to stop the spool from moving left or right but I don't think that should affect anything, right?
RE: Keep getting a filament stuck message on my MK4S
Just wanted to add another possible cause to the mix. I was getting errors, and the extruder was making bad noises while loading filament. Eventually, I found the problem by opening the tension latch and looking at the large gear that feeds the filament. The filament had completely missed the opening to the tube at the top end of the hotend assembly. It turns out that the bottom post of the main plate had broken off (don't know why) so the filament wasn't being guided to the tube opening properly.
If I manually guided the filament into the tube then closed the tensioner it prints fine. Obviously the main plate needs to be replaced. Fortunately, I found that the bag of spare parts has a spare main plate. I will use it, but I think I will also print my own main plate using the provided files. I noticed that the original part has only about 2 walls and pretty low density infill. I will print one that is all walls to make it stronger. Hopefully it won't break again.
Ready for a solution to fix stuck/jamming filament in Extruder??
I did investigate the last weeks many hours to get that issue fixed.
Since a week I'm printing one model after another WITHOUT ISSUES!!
Multimaterial prints with more than 600 tool changes, inside active heated chamber!!
Also Prints with more than 24hours printing!!!
before I fixed it, I never had a chance to do this, always stucking or jamming Filament, at least after some hours or while unloading, and then the toolhead was slightliy at a wrong position from the MMU attempt to get the filament free...
You must do 3 changes!!
1. replacing the grooved idler bearings
2. printing a modified Mainplate (this one fixes the jamming while unload, and so some layher shifting)
3. modifing the two idler screws to guarantee a smooth idler movement.
All details and details to the issue and the root causes can be found here:
https://www.printables.com/model/1059347-mk4mk4s-with-mmu-main-plate-with-improovement-step
Greets, Thorsten
RE:
Thank you for creating this mod. I won't be using it yet. I replaced the Main Plate with the spare that came with the upgrade it. However, if it breaks, I will certainly be looking to replace it with your design.
I haven't had any issues with the grooved idler bearings or idler screws so far, but I will keep them in mind for the future.
FYI, I've never had any issues with jamming during filament unload, only misfeeding of the filament while loading.
RE: Keep getting a filament stuck message on my MK4S
Hi Steve, misfeeding filament while loading? You mean that it seems, that the filament is not reaching the heatbbreak tube?
That is also an artefact of the grooved bearings, espacially if the idler springs has more tension, then the filament jumps into the groove of the bearing, which is approx. 0.6mm outside of the filament part and then the filament hits the bottom of the main plate, or what me happend one time was, that the filament tip was turn aside and came out, under the idler hinge and hit the upper thumb screw. But this extreme case I had only once and I was not able to reconstruct.
A very common sympthom I observed, that due to the flattend filament at the pulley, a small amount of filament left over at the main plate filament entry at the top, and if you try to load the filament now, then often the filament sensor does not react, becasue on load, the small filament piece then falls down to the idler hinge and blocks then the idler to be moved correctly.
That symptom was the main reason, why I redisigned the main plate, and the main plate takes only this into account, because the issue starts while unloading the previous filament.
Another tip I have here, if you add the 4. hole at the PG cover or rotate it 180°, you can screw out the set screw of the idler lever and remove the idler to get all fillament parts out. This is alos possible mid print, becasue you don`t need to remove the PG and the pulley.
RE: Keep getting a filament stuck message on my MK4S
In my case what happened is that the filament went down the side of the feed tube, because the bottom guide post of the Main Plate had broken off. With the spare Main Plate installed the filament is feeding just fine.
RE: Keep getting a filament stuck message on my MK4S
Having the exact same problem. All the proposed solutions in this thread haven't worked so far, as well as many others. I've detailed my situation in another thread
Now waiting on a spare nozzle to arrive to see wheter that is the problem, I've run out of ideas, nothing works.
RE: Keep getting a filament stuck message on my MK4S
I have now also ordered a new nozzle. But it can't be that it is already broken after 4kg of PLA.
RE: Keep getting a filament stuck message on my MK4S
What I also noticed: In the hardware settings in Prusa-Connect, high-flow was set to "off". But the MK4S has high-flow nozzles. I set it to 100% when setting it up. Maybe it went off after the firmware update? I set it back to ON, and it's been printing for an hour now. I hope it stays that way.
RE: Keep getting a filament stuck message on my MK4S
OK. I was too happy too soon, after 50% (4 hours) the error came back. So far it's been fixed once and it's still printing. I read somewhere that it does the detection via the load cell. Could it be that there's a problem there?? Please PRUSA, so many people have this, can you take a look?