I am at a complete loss, MMU2S fails to even fail consistently
My first printer was a MK/2S purchased assembled and it was wonderful. My second was the MK/3, bought as an upgrade kit. I took everything apart and put it all together and it was even more amazing. My basement is a bit on the chilly side so I built a Lack table enclosure for my printer. My printers have gotten thousands of hours of use just in the past year by myself and my two oldest boys who are 8 and 12. Along the way I've learned lots of tricks, like always check the first Z-layer to make sure everything looks nice an smooth, how to adjust the belt tension when I got it wrong, learning to be careful with nylon bolts on the z-axis after mine seem to have gotten cross-threaded, jury rigging the fan when I missed a piece, fixing a broken idler door, dealing with every kind of jam and failure, etc.
I bought the MMU2S excited to try my hand at some multi-color items. I'm especially fond of designing prints that change colors on layer heights, so even if it just saved me the trouble of switching colors manually on each M600 gcode, that'd be worth it for me. However, after going through the assembly on this one, I can't even get it to fail consistently. Therefore, I assume I have multiple interfering problems causing the MMU2S to work poorly and I don't even know where to start.
There are blink codes being shown by the unit that are not described anywhere in the documentation (e.g., what's a long red, short green mean?). The filament loads fine sometimes the first time I load it, especially right after boot, but usually it doesn't even leave the MMU. If it leaves the MMU, it often can't make it into the extruder and gets pulled back. If it gets pulled back telling the MMU that to try again by pressing the middle button often does nothing. Often it just gets stuck showing loading on the screen and I can't do anything without reseting the whole unit and starting over again. The calibration of the new IR sensor is extremely finicky. I have to jiggle the chimney to within microns of the right position and then hope that tightening the screws doesn't throw it off. I have to tweak the adjustment of the idler hinge screw and the idler tension screw as well in the process. There are so many variables. How can I possibly even start to get that right? I've had the FINDA probe get stuck on even when I've physically removed the FINDA from the MMU. There are little globs of filament everywhere that may be interfering with the operation of the unit, but even without I'm having problems so they aren't working.
And don't even get me started on how annoying the buffer is.
I'm so frustrated at this point. I was so excited to give the MMU a try, but now I'm on the verge of chucking it through a window. I've even tried 3 different firmwares on the off chance the inconsistency was some software thing, but no.
It would be EXTREMELY HELPFUL if the unit showed the status of the FINDA and IR sensors while loading so I can get feedback as to what the firmware is seeing. That's why the PINDA has an LED in it right? So I can clearly tell that bed leveling is doing what it's supposed to be doing. Why doesn't the FINDA LED light up? It has one, doesn't it? Why is there no status light for the IR sensor? A simple debug mode like that would be WONDERFUL. Fully documenting all the possible blink codes the MMU can have would also be a great thing. Fast red blink and slow red blink and all lights blink are definitely not the only error codes I've seen.
Now, aside from my suggestions above for Prusa, where do I begin to get my MMU working? I literally have no idea where to start. The troubleshooting helps I've seen assume you have one problem. I seem to have 6 or 7.
Cheers.
RE: I am at a complete loss, MMU2S fails to even fail consistently
Finda has a light that works.
if all else fails. you can just "preheat" then run filament to nozzle to test stuff. I would take it 1 path at a time. to work out the kinks. no need to go hog wild and start doing 5 filament prints if you have issues. just start with 2
I have a Prusa,therefore I research.
RE: I am at a complete loss, MMU2S fails to even fail consistently
I believe the Finda should be lit when filament is absent and dark when fiament is present, so if yours is always dark, it's probably screwed in too far....
remove all filament and see what the finda shows... should be lit... if not, try loosening the finda and moving it outwards awy from the filament pathway... may be worth taking it all the way out, and making sure the ball bearing beneath it, moves freely, and moves when filament is inserted (tip... for testing the finda, visually, you can pop the filament in from the front (Wrong way round)
if your finda does not light when it is powered on but not near the ball bearing (or any metal) then the finda is probably in the wrong connector slot, or faulty...
If metal makes the finda light go out, try re adjusting the finda in the MMU2, so it's lit when there is no filament present and dark when there is filament present...
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: I am at a complete loss, MMU2S fails to even fail consistently
FINDA has indicator light too, but is quite dim and not clearly visible. Remove FINDA from holder and try it on some metal, it can be faulty.
If you upgraded from MK2/S, you should have old PINDA probe. It is same type, so you can try it as replacement (not sure if it has same connector).
IR sensor and it's settings was the main cause of most of my failed filament loads. For troubleshooting you can try add indicator like this. It helps me set it correctly.
RE: I am at a complete loss, MMU2S fails to even fail consistently
If you want to check the status of sensors you can go to the menu -> support -> sensor info
There you have the status of FINDA, PINDA and Filament sensors.
I also had a lot of problems with the MMU. In my case many of them have been because the spool holders (I have no space enough to the suggested system)
In your case I would do:
1- Clean MMU. Open it and ensure there are no filament particles.
2- Find a big place and mount the printer as is suggested by prusa. It was helpful for me to discover that my problem were the "custom" spool holders.
3- Flash firmware to 3.7.1. I found a problem in the 3.7 and my printer was not loading the filament.
4- Factory Reset MMU ( https://manual.prusa3d.com/Guide/Service+menu+-+Factory+Reset/871)
5- Calibrate IR. With the 3.7 firmware was impossible for me to calibrate it. So with a non bugged version you will need to do it again ( https://help.prusa3d.com/article/wprwemqsmj-ir-filament-sensor-calibration)
6- Check MMU Cover screws tension.
RE: I am at a complete loss, MMU2S fails to even fail consistently
I must've really missed something during assembly. I didn't even know there was an IR sensor calibration!
.. and I've never noticed a FINDA light.. and I've had many troubles with "unloading". Once it fixed itself when I loosened the FINDA, pulled it up a fraction, and then put it down again..
RE: I am at a complete loss, MMU2S fails to even fail consistently
Check if the funds works properly.
Try FINDA with piece of metal as joantabb suggested checking the status in the sensor info menu.
Mine was broken and I needed to ask for a new one to the customer service.
RE: I am at a complete loss, MMU2S fails to even fail consistently
@toaf I have never noticed the LED on the FINDA lighting. I have noticed the Sensor screen under Support showing 1 and sticking there after it has trouble loading, even after taking the FINDA out of the socket. It generally seems to work correctly when I slide filament in and out otherwise. That problem felt like a firmware glitch, but I'm thinking the LED might be out on mine. Maybe I can try reseating the connector. I may also try my old PINDA from the MK/2S and see how that work. That's a good idea. Thanks.
@parkis I may try the LED idea, though I'm somewhere afraid to do it because my soldering skills are not so good. I only have through-hole LEDs with domes, but it should work just as well if I replace a leg with a resistor. It won't be as pretty as yours. It would have been extremely helpful if that had been part of the supplied sensor module. It's hard to know if the IR sensor is still calibrated correctly or having some other problem (such as a glob of filament wedged in the idler) during a loading problem without any feedback at all. Thanks.
@giskard I've flashed 3.6.0, 3.7.0, and 3.7.1 and my performance has been the same with each. I need to re-flash it back to 3.7.1 as 3.6.0 was the last thing I tried. I work pretty hard at only changing one thing (just firm, just FINDA adjustment, just IR sensor adjustment, etc.) between each test, but nothing has made a clear difference. I have factory reset the MMU after each flash just to get to a clean state. I've done each of the things you suggest in turn, but they haven't seem to have made much difference. Thanks.
Thanks everyone, @kieran-s4 and @joantabb as well. Now that I've rested and had some time away from it, I'm ready to try my hand at it again tonight. Hopefully one of these suggestions will help.
RE: I am at a complete loss, MMU2S fails to even fail consistently
I finally had time to go back and take another look at this. It's been such a busy week.
Anyway, my FINDA never lights under any circumstances, not even a tiny bit. I put it on 5V and my DVM on it by itself and it outputs 5V on the signal line when filament is in place and 500mV otherwise. So that's perfectly reasonable. I guess the LED is just dead or broke. However, as a weird wrinkle to this tale, I got out my old PINDA from the Mk/2S and tested it on 5V and it lights up fine. BUT, when I plugged it into the MMU controller board, it does NOT light up. That seems wrong. I'll see if I can get my DVM in there and see what kind of power is being provided to the FINDA and see if something seems wrong there.
I added an LED to the IR sensor and it is WONDERFUL. (Mine is also horrifyingly ugly, but it works.) This is a world changing addition to the printer. Being able to see that made calibration much easier. That should be a standard feature for sure. The LCD display is good for telling you what the mobo sees, but is passing through the main controller and a bunch of software and down a drive to the LCD, so it's really not great feedback when what you really care about during calibration is what the sensor is seeing.
Anyway, I'm about to give this another shot, so we'll see what happens.
RE: I am at a complete loss, MMU2S fails to even fail consistently
I didn't get very far, but I think I made some progress.
- Whenever I do a Load to Nozzle, the IR sensor immediately went out of calibration. I don't know what that would be, but calibrating the sensor while it is trying to do that operation helped. I couldn't see this happening before because there's no indicator on the IR sensor. Someone from Prusa, PLEASE FIX.
- After futzing around, I realized that the MK2S PINDA as FINDA is actually lighting up, but it's super dim. The power supply I had was putting out about 5.5V, so I suspect the MMU is putting out something closer to 5.0V or something or something. I'd need a DVM or maybe a scope to see that more clearly (but I don't own a scope right now)
- .And now I'm sometimes getting all 5 LEDs flashing, so something I changed is now draining power or maybe it's just my firmware. I need to return it to 3.7.1 or whatever is the latest now to make sure that's okay. (I'd previously downgraded to 3.6.0 to see if that would change the behavior.)
The main conclusion, though, is if you're having trouble, strap an LED and 1K resistor across the the +5V and Signal lines of the IR sensor and save yourself a bunch of trouble.
RE: I am at a complete loss, MMU2S fails to even fail consistently
I didn't get very far, but I think I made some progress.
- Whenever I do a Load to Nozzle, the IR sensor immediately went out of calibration. I don't know what that would be, but calibrating the sensor while it is trying to do that operation helped. I couldn't see this happening before because there's no indicator on the IR sensor. Someone from Prusa, PLEASE FIX.
This sounds to me like you might have a wonky door where the arm isn't quite right. My IR sensor would test fine when I would insert filament or a hex key per the troubleshooting steps, but I couldn't get through a print without it tripping erroneously when I was testing without the MMU attached.
Someone posted a slightly modified door that you can sand down the arm to fit, I gave that a go and was actually able to get through a print with the sensor on and no false run out events. Additionally, this new door fits a bit looser and I can now manually feed filament down to the nozzle like I used to be able to do prior to the 3S upgrade.
Previously you mentioned frustration with the buffer. I'm in a situation where I simply didn't have the space for their suggested setup. I tried a few things and ultimately settled on an auto-rewind holder for my spools. One thing I noticed in my futzing was that the MMU seems to be REALLY particular about friction. If there is any resistance, then it starts getting upset. In my first pass with the auto-rewind spools I was using the included PTFE holder arm and the long PTFE tubes to go the the MMU (the ones that go between the buffer and MMU in Prusa's setup) and I couldn't even get it loaded as the arm moved too much and the curvature of the tube was too tight so the filament drug too much. I then ditched the arms and instead plugged the short tubes (between the spool and buffer in Prusa's setup) into the MMU. Since then 1 out of 269 tool changes has failed and that one recovered nicely (long hair attached to the outgoing filament).
RE: I am at a complete loss, MMU2S fails to even fail consistently
Whoa. As soon as I calibrated my IR sensor and enabled it.. I've had heaps of problems with the print stopping and the mk3's mmu2s telling me to reload filament!
I did 4 single filament temperature tower prints yesterday, and it happened at least 5 times. Each time, when lookingat the MMU2s, there was be 5cm of filament sticking out of it! What the hell! I had to manually pull it back so the selector didn't get jammed if it moved back into place!
I then uncoupled the push fitting on the extruder, pushed a hex key in and out, and monitored the status in the mk3's menu system. This shows the IR sensor was working as it should. Wha?
Something is up with it, it's sick. Clearly turning off when it shouldn't be, mid print.
RE: I am at a complete loss, MMU2S fails to even fail consistently
Now that I can clearly see the the IR sensor calibration with the LED I put on it, I can clearly see I'm screwed.
There simply is no way to properly calibrate the IR sensor. The parts provided do not work. Calibration itself cannot be done on mine with the idler tension set so that the M40 screw with the spring on it is "aligned or slightly below the surface" as the assembly instructions say. If the tension is that high, the idler cannot be moved at all with any reasonable level of force. The screw used as the hinge for the idler is loose. It's not tight at all, so that's not it either. I suspect that the MMU cannot force the filament in to open the idler enough to trigger the IR sensor on load either. Loosening the spring completely is about the only thing that helps. I think I need a spring with less tension. I've tried trading it out from springs from previous versions of this printer and they aren't any better.
Furthermore, the sensor goes permanently out of alignment whenever the E-axis moves. The chimney is not a stable platform for the sensor, not matter how I tighten it (I've tried barely tight, pretty tight, and tight-as-I-dare-with-PETG-parts with similar results), so even if I can figure out a way to get the IR sensor calibrated, I can't keep any calibration I set.
At this point, I think I need to print a completely new extruder, at least for all the parts the can move or be calibrated at the top. I may need a different idler spring at this point too.
@gnat I am planning to make some auto-retracting spools, but first I need a working MMU. I'm not even close to that at this point.
RE: I am at a complete loss, MMU2S fails to even fail consistently
@zostay
I had to use a fair bit of force to get the filament through as well.. but I just loosened the tension, while monitoring the IR sensor display in the menu.. and got it to a point where it seemed to be working.
But I can't sit there watching the screen for 45mins to catch what's happening when it fails.
Your led solution sounds really handy for troubleshooting.
RE: I am at a complete loss, MMU2S fails to even fail consistently
This new "can only edit for 5 mins" thing in this forum is B.S. I was pushing the hex key through (as suggested by the instructions), not the filament.
Who knows what that does to the gears!
RE: I am at a complete loss, MMU2S fails to even fail consistently
@zostay your idler door issues sound exactly like what I was going through. Try printing the new door that I linked to. Not only did it allow me to fine tune the arm to better trip the IR sensor, but the filament goes through the gears MUCH easier. Seriously, I couldn't push it through if the idler screw was in at all, now it resists but I can manually push down to the nozzle.
As far as the spools (and the idler door), disconnect the MMU and print out the first couple as a plain MK3S. I should have just added a switch to isolate the damn thing as many times as I removed it and reinstalled...
RE: I am at a complete loss, MMU2S fails to even fail consistently
So, shortly after my last post, within an hour or two, I got it to work and I now have a green sheep!
What I found was the problem was this (Bold text is the TLDR version):
- I upgraded to latest firmware, 3.7.1/1.0.5 and performed a factory reset on the MMU. I don't know if this really helped or not, but seemed sensible.
- The MMU idler was jamming when it tried to turn sometimes and this happens because of two different problems. First, my MMU idler was slight over-tensioned. I solved this problem by releasing tension on the MMU idler tension screws. Second, it happens because I had a habit of resting my hand on the top of the idler to push the buttons. The lesson here is: Resting my hand on the MMU idler increases the tension too high and causes jams, so stop doing that. The idler does not seem to recover from jamming gracefully. It would be nice to know if there was some trick to get the idler back into alignment after it has slipped out.
- The IR sensor calibration is impossible without the LED I added. I finally managed to get the IR sensor aligned, but it was very fiddly. Both forward and reverse motion on the E-axis moves the idler around on its axis, which causes the IR sensor to stop detecting properly for certain alignments. I had to carefully dink around with the calibration so that it worked with a test filament and when it was pulling forward and when it was retracting. My LED indicator dims on retraction, but it seems to work anyway.
- The filament sensor was disabled in my settings. I enabled the filament sensor. I hadn't checked because I've always had it on with the MK/3 and assumed it would stay on with the new firmware. Apparently not. I assume this makes a difference because things started working better for me after that (it stopped the load/immediately eject/load/immediately eject/fail cycle it frequently went through before).
- After performing IR sensor calibration, I increased extruder idler tension. I thought since I was having trouble putting the hex key in during calibration, that was a problem for loading. My intuition was wrong. I tightened the tension slightly further and the Bondtech gears are engaging more consistently rather than less. Part of the problem I was having with IR sensor calibration was that if I tried to calibrate after an error, the E-axis would lock up. I had to reset the printer whenever there was an error to make sure the E-axis remained free for IR sensor calibration. So, after failure, reset the printer and calibrate again. Do not try to calibrate after error because the E-axis must be free to move during calibration to the hex key to move the idler.
I believe that's everything I did. It was like magic when it suddenly started working. I really think my interfering problems were primarily the MMU idler tension being too high (partly because of my hand), the E-axis idler tension being too low, and having to adjust the IR sensor calibration to deal with the base state, forward extrusion, and reverse extrusion and carefully balancing the alignment for each of those. The most valuable lesson learned is indicator LEDs belong EVERYWHERE.
My son was able to print a striped gecko as well.
RE: I am at a complete loss, MMU2S fails to even fail consistently
It was like magic when it suddenly started working.
Congrats on finally getting it working. I can totally agree with that magic sentiment. It was like x-mas after all the pain when I came down in the morning and found a completed (one tool failure due to a string early on before bed) 2 color Benchy.
RE: I am at a complete loss, MMU2S fails to even fail consistently
this post gives me hope, after struggling some day I printed succeffully 2 color bechy and a parte made with PLA + BVOH... then my MMU started a spiral of clogs, failed loads ant any fix I've been trying taken me to worse results... I'm currenlty failing even some single color print (when changing the filament at the befogging of the print)
RE: I am at a complete loss, MMU2S fails to even fail consistently
I finally had time to go back and take another look at this. It's been such a busy week.
Anyway, my FINDA never lights under any circumstances, not even a tiny bit. I put it on 5V and my DVM on it by itself and it outputs 5V on the signal line when filament is in place and 500mV otherwise. So that's perfectly reasonable. I guess the LED is just dead or broke. However, as a weird wrinkle to this tale, I got out my old PINDA from the Mk/2S and tested it on 5V and it lights up fine. BUT, when I plugged it into the MMU controller board, it does NOT light up. That seems wrong. I'll see if I can get my DVM in there and see what kind of power is being provided to the FINDA and see if something seems wrong there.
I added an LED to the IR sensor and it is WONDERFUL. (Mine is also horrifyingly ugly, but it works.) This is a world changing addition to the printer. Being able to see that made calibration much easier. That should be a standard feature for sure. The LCD display is good for telling you what the mobo sees, but is passing through the main controller and a bunch of software and down a drive to the LCD, so it's really not great feedback when what you really care about during calibration is what the sensor is seeing.
Anyway, I'm about to give this another shot, so we'll see what happens.
1) Same happen to me... my FINDA is not showing the LED... but seems to work fine... it detects the filament.
2) How did you added the LED to IR detector?
3) Like you, I have lot of problems with MMU2S, filament load fails almost 50% of times.