Bits of filament get stuck in filament sensor
Hi there.
Every few filament chages I face the issue that the steel ball of the filament sensor gets stuck and as a result the printer detects a filament, that is not there. Sensor readings are about 30000 when filament is loaded and about 187000 when filament is unloaded and the steel ball is not stuck. But when the filament is stuck, the sensor readings can be anything in between so that it constantly detects filament even if there's none inside.
(recalibration in this state might be a workaround but I'd rather have the cause fixed than the problem)
I can only resolve the issue by poking around in the sensor with filament until the steel ball comes out eventually.
Does someone have an idea where those bits of filament come from? I currently don't have an explanation for it. Never had any issues with my Prusa mk3 but the mk4 is making loads of trouble. 😤
One cause is leaving the filament too long after the unload bleep - it starts with a slight blob but in time it necks and a mini blob is connected by a wasp-waist to the end of the filament, it breaks off easily.
Cheerio,
RE: Bits of filament get stuck in filament sensor
Hm but that's not how the mk4 unload routine works in my opinion. When I unload filament it deliberately takes its time to very slowly pull out the filament so that it comes out clean. Then after a few seconds it finally releases it. But by this time its already cooled down so it doesn't matter how quickly I pull it out. If there's residue in form of small bits left behind there would be not much I can do about it.
Am I wrong?
RE:
I just checked.. There is not even a beep after the unload. Also no request to pull out the filament. I just performed a recalibration while the steel ball was stuck to make it a little bit more sensitive in this state and hopefully fix the issue by software this way. But that also doesn't work because of a firmware bug. https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/3239 🙄
OK, I'm used to seeing the effect described above on my Mk3 and it's a common cause of load errors, occasional filament sensor errors too but that's more often a fine strand of stringing.
If recalibration temporarily fixes it then I would try calibration at different temperatures and compare the results.
Cheerio,
RE: Bits of filament get stuck in filament sensor
Can someone confirm that this is also an issue on their printer? Does someone have an idea what's the cause of this? It's really annoying and prusa support isn't helping me. 😐 I never had an issue with my mk3.
RE:
I'm confused about nobody answering here. Does it mean that nobody else has this issue? What could be wrong with my machine then?
RE: Bits of filament get stuck in filament sensor
I have now and then also Sensor problems after unload and need to push manually to get it working. I did not disassemble the sensor and did not find any debris up to now - but it could be that there is something hidden.
I think this is one of the problems Prusa is experiencing with the MMU3 and there will be a fix (SW and HW) for this.
RE:
Prusa have developed a new way to eject and unload filament that does not leave loose strands etc at the end when releasing, since this would have a huge impact on the use of the MMU3, where filament is unloaded and loaded automatically. Hopefully the fix will be implemented in the next firmware update.....
RE: Bits of filament get stuck in filament sensor
Interesting. I just read the official blog article. https://blog.prusa3d.com/development-diary-update-on-mmu3-for-the-mk4_85043/
Another slightly less common problem is the filament sensor on the MMU3 unit itself not triggering correctly. Since this sensor is working perfectly with the MK3S+, the problem is most likely caused by tiny pieces of debris still being sometimes generated by filament loads – this may cause the FINDA ball to get stuck on unload.
RE: Bits of filament get stuck in filament sensor
I do not understand how this (tip tuning by SW) will work on the millions of different filament.
RE: Bits of filament get stuck in filament sensor
I thought it was because its changing the tip of the filament to remove the remaining whisps - hence when pulling it out it will be much 'cleaner' and not leave such debris. I'm assuming it would apply irrespective of the type of filament used?.....
RE: Bits of filament get stuck in filament sensor
Right - the new unload procedure (as described in the Prusa report) did improve the tips of the filament a lot. But Prusa cannot check on thousands of different material. Therefore I'm sure there will be some remaining adjustments to do for the user.
RE: Bits of filament get stuck in filament sensor
I have the same problem !! I already had to clean the sensor twice: it had little pieces of filament in it and was malfunctioning !!
I also have the firmware 5.0.0. I hope the next FW upgrade will amend the unload process to avoid that in the future...
RE: Bits of filament get stuck in filament sensor
Checking in to say that I have started to encounter this on my MK4. Has anyone found a good solution?
RE: Bits of filament get stuck in filament sensor
Right, I also have this problem for the second time. The first time it was enough to push and pull a hex key down into the filament hole a few times and the steel ball popped out, but this time the trick doesn't work, seems like I'll have to partially disassemble the extruder to fix it.
It's not a deadly issue, more like an inconvenience, but that's annoying.