How to fix filament jam on MMU2S?
I upgraded to MMU2S / MK3S, and of course nothing works. But specifically, trying to print my first two-tone Benchy:
- I receive the message "MMU needs user attention". No idea what this means.
- The Red LED is blinking over filament #2, and the filament appears to be loaded into the selector and feed tube, all the way to the extruder.
- So I tried to follow this manual , since no equivalent manual exists for the MU2S. But that manual refers to the old extruder, with the easily opened idler hatch. Of course on the new-and-improved extruder, this hatch can't be opened without disassembling the filament detector and ruining the (already precarious) calibration.
- Nevertheless, somehow I managed to eject the problematic filament (which had no actual defects that I could see). I trim off about a meter and re-feed it into the MMU2. It appears to load correctly (not past the selector).
Now the selector is empty, the MMU2 is loaded, the red led over filament #2 is still blinking (slowly?), and "MMU need user attention" is still on the printer's LCD screen. And I still have no idea what this means.
Prusa, some guidance on how to work around the many, many glaringly obvious defects of the MMU2 would be appreciated. Having to do this fifteen times just to print a single two-color benchy is getting tiresome.
RE: How to fix filament jam on MMU2S?
Apparently, "solve issue, then press button on MMU unit" means press the reset button, and not any of the other obvious buttons.
RE: How to fix filament jam on MMU2S?
Yay! The printer successfully printed a single layer. Then there was a loud clicking noise from the MMU.
... Now all the LEDs on the MMU are blinking red.
Yay.
RE: How to fix filament jam on MMU2S?
- I receive the message "MMU needs user attention". No idea what this means.
To be a little glib, it means the MMU is unhappy and needs to be looked at.
- The Red LED is blinking over filament #2, and the filament appears to be loaded into the selector and feed tube, all the way to the extruder.
In such a situation there are 2 modes of blink and them mean different things. Slow should be that there was an unload issue and fast would be a loading issue (or it could be reversed, I haven't had to look it up much).
- So I tried to follow this manual , since no equivalent manual exists for the MU2S. But that manual refers to the old extruder, with the easily opened idler hatch. Of course on the new-and-improved extruder, this hatch can't be opened without disassembling the filament detector and ruining the (already precarious) calibration.
Actually you can remove the door pretty easily. Remove the tension bolt as usual. Then remove the bolt that acts as the axle for the door itself. In the new extruder design it is accessible without removing the extruder from the X axis.
Definitely not as easy to get in there as the non-MMU variant though which I agree is annoying.
- Nevertheless, somehow I managed to eject the problematic filament (which had no actual defects that I could see). I trim off about a meter and re-feed it into the MMU2. It appears to load correctly (not past the selector).
Now the selector is empty, the MMU2 is loaded, the red led over filament #2 is still blinking (slowly?), and "MMU need user attention" is still on the printer's LCD screen. And I still have no idea what this means.
Yeah early on I had similar issues and ended up randomly pressing the 3 MMU buttons until it cleared. Be careful pressing the left or right buttons twice in a row too quickly as that will move the selector (just double press the other button to move it back).
RE: How to fix filament jam on MMU2S?
Yay! The printer successfully printed a single layer. Then there was a loud clicking noise from the MMU.
... Now all the LEDs on the MMU are blinking red.
Yay.
Your issues sound almost identical to what I was experiencing. Suggestions I would make:
- Make sure there is as little drag in the path from the spool to the MMU as possible. Make any curves in PTFE tubes are as gentle as possible.
- I ditched the buffer and used auto-rewind spools instead: https://www.thingiverse.com/thing:3338467
- With those spool holders I just used the short PTFE tubes in the back of the MMU rather than the long ones.
- Disconnect the MMU and dial the printer in as a MK3S (e.g. calibration, Live Z, etc..).
- Get through an entire print with the IR sensor enabled and no false run out events.
- I couldn't get through a 20x20x20mm cube until I replaced my idler door with https://www.thingiverse.com/thing:3572252
- Reconnect the MMU and verify a single filament print.
- Then try a two color print
Friction in my filament path (it really doesn't seem to take much) and the idler door are what I believe were my issues.
RE: How to fix filament jam on MMU2S?
Another friction related thing I noticed, the idler door on the MMU likes to be loose. I started just barely getting the tensioner bolts in and it seemed to play happier with me.
RE: How to fix filament jam on MMU2S?
Also for reference there's the Troubleshooting guide of the handbook:
https://www.prusa3d.com/drivers/
http://prusa3d.com/downloads/manual/prusa3d_manual_mmu2s_eng_1_00.pdf?2
The middle button is the correct one.
There are many possible errors - it requires some patience to get them sorted out.
Printing https://www.thingiverse.com/thing:3528314
and playing with it for a while with a bend piece of filament was enlightening. If filament bends and the bend goes in the wrong direction it can get stuck - the placement of spools/tubes is important.
RE: How to fix filament jam on MMU2S?
Dude, thank God for you, and community members like you. I will do all of these things.
RE: How to fix filament jam on MMU2S?
- Disconnect the MMU and dial the printer in as a MK3S (e.g. calibration, Live Z, etc..).
Does this mean I need to downgrade the firmware to non-MMU firmware? Will it still be happy with the IR filament detector?
RE: How to fix filament jam on MMU2S?
Apparently there is no "non-MMU" firmware, and no, the IR sensor won't work to trigger the autoload or runout functionality with the MMU disconnected. (Even though the IR sensor sees the filament, autoload doesn't start).
Guess I'll load manually.
RE: How to fix filament jam on MMU2S?
Apparently there is no "non-MMU" firmware, and no, the IR sensor won't work to trigger the autoload or runout functionality with the MMU disconnected. (Even though the IR sensor sees the filament, autoload doesn't start).
No there is no separate firmware for the printer based on if the MMU is connected or not.
Go into Settings and make sure the filament sensor is on and autoload is also on. If both are on and it is not loading, then you definitely have an issue with your IR sensor and that is not helping your MMU woes at all.
In there Support menu there is a Sensor Status item that will show you the state of the IR sensor. It should be 1 when there is no filament and 0 when it is present. If that value is not changing:
- Loosen the idler door as much as you can and try again.
- Maybe you just have it too tight.
- Remove the tensioner bolt completely and try moving the door (pull the bottom outward) to see if the value changes.
- This could be a sign that you want to try printing a new door. Yours may be like mine and be too tight of a fit.
- Remove the bolt that holds the idler door in place and remove the door, then try to trip the IR sensor yourself by sticking a piece of filament into it.
- Another sign that maybe you need a new door with an eye on finessing the IR flag at the end of the arm.
- Double check your connection both on the IR board and the main board.
- Contact Support as you may have a bad IR sensor.
If you do see the value change:
- Go into Settings and Disable Steppers
- Go back to the sensor status
- Wiggle the filament around and look for the status to change.
- Move the X axis back and forth similar to if it was printing and watch the status.
The status should stay constant in those cases. If it does not (even briefly) then you should probably print a new door and give that a try.
RE: How to fix filament jam on MMU2S?
Also for reference there's the Troubleshooting guide of the handbook:
https://www.prusa3d.com/drivers/
http://prusa3d.com/downloads/manual/prusa3d_manual_mmu2s_eng_1_00.pdf?2
The middle button is the correct one.
Thanks for this link. This is the manual I was using. When the MMU is in this state, the middle button (in my case) does nothing at all, as far as I can tell. Only thing that got the MMU out of zombie mode was resetting it, after which the print resumed (for one layer).
RE: How to fix filament jam on MMU2S?
Apparently there is no "non-MMU" firmware, and no, the IR sensor won't work to trigger the autoload or runout functionality with the MMU disconnected. (Even though the IR sensor sees the filament, autoload doesn't start).
Go into Settings and make sure the filament sensor is on and autoload is also on. If both are on and it is not loading, then you definitely have an issue with your IR sensor and that is not helping your MMU woes at all.
In there Support menu there is a Sensor Status item that will show you the state of the IR sensor. It should be 1 when there is no filament and 0 when it is present.
Yep, The Support > Sensor status menu was showing that the filament sensor was at 1 (with filament inserted), but Autoload wasn't triggering. Maybe I messed something up (MMU was not disconnected properly from the RAMBO board, or I forgot to preheat or something). Once I did a manual load with the MMU disconnected, everything worked fine, and single-material Benchy is printing now.
I'll try again once this print is done. Thanks for all your help!
RE: How to fix filament jam on MMU2S?
(Side note: Since this has evolved into a general troubleshooting thread for MMU2, maybe some generous, charitable, handsome moderator could change the title of the thread?)
RE: How to fix filament jam on MMU2S?
Apparently there is no "non-MMU" firmware, and no, the IR sensor won't work to trigger the autoload or runout functionality with the MMU disconnected. (Even though the IR sensor sees the filament, autoload doesn't start).
Go into Settings and make sure the filament sensor is on and autoload is also on. If both are on and it is not loading, then you definitely have an issue with your IR sensor and that is not helping your MMU woes at all.
In there Support menu there is a Sensor Status item that will show you the state of the IR sensor. It should be 1 when there is no filament and 0 when it is present.
Yep, The Support > Sensor status menu was showing that the filament sensor was at 1 (with filament inserted), but Autoload wasn't triggering. Maybe I messed something up (MMU was not disconnected properly from the RAMBO board, or I forgot to preheat or something). Once I did a manual load with the MMU disconnected, everything worked fine, and single-material Benchy is printing now.
I'll try again once this print is done. Thanks for all your help!
Disconnected means that other than still attached to the frame (optional) it should otherwise be disconnected from the printer and unpowered. I have no idea how the IR sensor and autoload would act with the MMU connected, but trying to feed filament directly to the extruder...
RE: How to fix filament jam on MMU2S?
I enabled the IR sensor during the print, and the printer immediately stopped (false positive runout detection). While I was unloading / reloading the filament, I loosened the idler door and door hinge screw as you suggested, and there hasn't been another false-positive runout detection since then (about twenty minutes ago).
I am cautiously optimistic!
RE: How to fix filament jam on MMU2S?
Disconnected means that other than still attached to the frame (optional) it should otherwise be disconnected from the printer and unpowered. I have no idea how the IR sensor and autoload would act with the MMU connected, but trying to feed filament directly to the extruder...
Yeah, I figured it out eventually, after a facepalm or two. Now the MMU is properly disconnected, benchy is printing, and the IR sensor is enabled.
RE: How to fix filament jam on MMU2S?
I enabled the IR sensor during the print, and the printer immediately stopped (false positive runout detection). While I was unloading / reloading the filament, I loosened the idler door and door hinge screw as you suggested, and there hasn't been another false-positive runout detection since then (about twenty minutes ago).
I am cautiously optimistic!
The hinge bolt shouldn't be loose while it's printing as it's primary function is to hold onto the extruder motor. Removing that bolt is just to allow you to test the IR sensor separate from potential door related issues.
RE: How to fix filament jam on MMU2S?
I enabled the IR sensor during the print, and the printer immediately stopped (false positive runout detection). While I was unloading / reloading the filament, I loosened the idler door and door hinge screw as you suggested, and there hasn't been another false-positive runout detection since then (about twenty minutes ago).
I am cautiously optimistic!
The hinge bolt shouldn't be loose while it's printing as it's primary function is to hold onto the extruder motor. Removing that bolt is just to allow you to test the IR sensor separate from potential door related issues.
Oh I didn't remove it. Just loosened it a half-turn or so. It's still very much attached.
RE: How to fix filament jam on MMU2S?
Okay, benchy is done. Now I removed the idler door, to see if I can get a filament to go all the way through to the hot end without any friction.
Verdict: Not really. Without the idler on, the filament still engages with the bondtech gear on the extruder motor. When I push on the filament, the motor shaft turns. I don't actually know if this is normal, but on my mk3, I would have been able to slide the filament past the gear. On this extruder, it's no-go. The filament engages the bondtech gear, then if I push it hard enough, it will keep going (motor shaft turning) into the hot end.
Is this normal? I can post a video or something if it helps..