MMU Aborting seemingly successful loads
See video: https://photos.app.goo.gl/pMtbaBeE4sJfdZ3v9
I thought I finally had my MMU all dialed in/working reliably, then this started happening. It's continually 'failing' to load filament... but as far as I can tell, it's not actually failing and it has no reason to think that it is. You can see it move the filament in, the extruder gears grab the filament, the IR and FINDA both detect that the filament is where it should be... and then a few seconds later, it backs the filament out anyways and starts over. Does anyone have any idea what's going on here?
RE: MMU Aborting seemingly successful loads
First of all, what is up with your FINDA reporting N/A? It should either be 0 (no filament) or 1 (filament). I've heard about a new revision of the filament sensor coming with new printers, do you have that? If not (or if that's not how it is supposed to act), then I would say your first step is to figure out why the FINDA is not reading correctly.
Assuming your FINDA is working correctly (showing N/A instead of 0), then there are two cases that I've experienced this. The first is that the FINDA flakes out and thinks there is no filament present. This can happen due to the FINDA depth not being quite right or an issue with the filament itself (e.g. the MMU eating a chunk out of the filament). If you are sure of the FINDA and the filament, then it's your IR sensor. It's not adjusted correctly and ends up sending a false no filament signal, the MMU sees that the FINDA disagrees, so it retracts and tries again.
If you haven't already said it, you are likely thinking of pointing out that the support menu showed both reporting filament. The support menu view of the sensors is not reliable as it is on a rather slow (in computing terms) loop to refresh the delay. The FINDA/IR states can flicker a couple of times in between LCD refreshes and you won't see it. There is a (dim) light on the FINDA that you can watch to see what it is doing (lit when no filament is present and off when it is there). There is a mod documented in the Mod subforum for adding a LED to the IR sensor which DRASTICALLY improves your ability to figure out what is going on with it.
RE: MMU Aborting seemingly successful loads
Exactly same issue here. it has been printing for the last 3 days quite fine... and now midprint it started doing exactly like your video... with N/a and all
RE: MMU Aborting seemingly successful loads
@marius-helmeseanu
N/A means that there is a contact fault. I would check all the connectors on the back of MMU2. Also the connectors on the Einsyboard. Possibly the sensor also has a loose contact.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: MMU Aborting seemingly successful loads
Hi Karl,
Unfortunately no luck...I checked all cables, factory reset the mmu but still nothing...
Here's a video with how it currently works... i observed that imediately after the IR is triggered the extruder pushes back the filament causing the ir to not get triggered...
RE: MMU Aborting seemingly successful loads
@marius-helmeseanu
Very interessting! I would still try to reflash the FW of the printer and the MMU2 (make sure you have the correct version - MK3 or MK3S) including factory reset. If that does not work I would contact the Prusachat. To do this you have to log in with your account at prusa and go to the eshop. there you will see the chat window in the lower right corner.
good luck!
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: MMU Aborting seemingly successful loads
okay... so I just managed to find the issue. it was not electrical or mechanical...it was a blocked hotend 😐
seems that my printer detected it could not push the filament further in the hotend and decided to just not try :))
RE: MMU Aborting seemingly successful loads
after 3 successful prints I can confirm what I said above 🙂 no more issues
RE: MMU Aborting seemingly successful loads
@marius-helmeseanu
Thanks for the feedback!
Very interesting. A blocked hotend causes such errors. You never finish learning.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: MMU Aborting seemingly successful loads
okay... so I just managed to find the issue. it was not electrical or mechanical...it was a blocked hotend 😐
seems that my printer detected it could not push the filament further in the hotend and decided to just not try :))
I accept that your extruder was clogged and that now that it is clear your tool changes are working.
I don't understand how though. From your video you appear to have a MK3S which has the IR sensor rather than old laser of the plain MK3. The IR and FINDA are both simple on/off sensors, so there is no way for them to know if the filament is moving or not.
At a guess I think your IR sensor is not tuned perfectly and the vibrations of the bondtech gears slipping when they couldn't feed filament futher was causing the flag to pop out of IR field just enough to confuse the MMU.
I'm a firm believer (especially with the MMU) in the "if it ain't broke, don't f..k with it" approach, but you might keep this in mind for the future when/if you start seeing other random weirdness that could be IR sensor related.
RE: MMU Aborting seemingly successful loads
@gnat
I fully agree with you i thought as well the ir was not ok. I did the calibration several times. I changed the ir with another one and no change.
the blockage issue clicked for me when i realized the bontech gears were grinding the filament a lot.
i belive ghe gears were grinding so much that the filament diametre became so small the ir was no longer triggered resulting in the load failure.
i will definetely not touch it unless i start gaving issues again 😀
RE: MMU Aborting seemingly successful loads
Still having the issue - if there's an IR calibration issue I can't seem to figure out what it is/how to fix it, short of the LED mod which I'm really not confident in my soldering skills enough to try. If the screen really is incorrect due to polling rate, I do wonder if they could update the firmware to somehow realize "No the user isn't standing there rapidly pulling the filament in and out, this sensor setup is just incredibly flakey"
RE: MMU Aborting seemingly successful loads
edit-thats-a-new-post-because-of-the-edit-timer:
On further fiddling, I do think it might be an issue with my filament tips, in that it does seem to often finally succeed after the MMU 'gives up' and uses the knife to cut off the tip of the filament. However, that raises another question: Does anyone know what actually determines when it finally decides to employ the cutter? I've noticed the bizarre behavior where it tries to load a bunch of times, gives up and then uses the knife and successfully loads, while other times it goes straight into 'mmu needs attention' mode without employing the knife at all. (For extra weirdness, in at least one of the latter instances pushing the right button on the mmu caused it to immediately use the knife and load successfully, so, like... why didn't you do that before calling me over?)
RE: MMU Aborting seemingly successful loads
Update: I did eventually give in and go with the LED mod. gnat was correct in that the screen seems to simply not be accurate enough for actually debugging IR sensor issues. Of course, now I'm having UNload issues where the printer simply seems to entirely ignore the input from the IR sensor, but that's an issue for another thread...