Is there no way to recover a print with MMU2 after filament runs out?
I cannot find a way to make my MMU2 MK3S resume printing after my spool ran out.
Printing stopped as one would expect, though with the tube from extruder to MMU still full.
I inserted a new spool and fed the filament up and through the MMU, and part way down to the extruder (after manually removing the old piece of filament between the extruder and MMU (cold) without difficulty.
Pressing the switch on the printer to resume temperatures, then pressing the mid button on the MMU, the MMU withdrew the filament about 100mm and stopped. Repeating pressing the mid button, it withdraws another 100mm. One can hear the filament detector operating when expected.
It ought to know to feed the filament toward the extruder, but it does not. Manually pushing the filament until it activates the sensor in the extruder does not get past this problem. The MMU only knows to retract 100mm, and never tries to resume.
Surely it's possible and indeed common to reload the printer upon running out of filament? I know about splitjoin(?) but the other 4 positions are loaded with other filaments, I don't want to dedicate one position to a new spool of the same filament that runs out.
What can I try?
Do I really have to start the whole print over? Sheesh.
Best Answer by kpreid:
Two things that might help:
- If the filament runs out, what should happen is that the MMU retracts the filament, moves the selector aside, and “ejects” the filament (sticking the end out into air) so you can remove the remaining piece. If that didn't happen, then something went wrong with the unload — possibly the tail end of the filament had a bend in it and got jammed while trying to retract, but you say the MMU was able to retract so perhaps that isn't the problem.
- In order to resume a print when the MMU (as opposed to the printer) thinks something is wrong but you've now corrected it, you need to push the right (not middle) button on the MMU. The middle button only does “recheck/retry” and the right button is “resume”.
My MMU has handled several filament run-outs or breaks, but I know other people have had trouble with the same steps. Sorry I don't have an “aha, this is exactly problem and solution” answer.
RE: Is there no way to recover a print with MMU2 after filament runs out?
Two things that might help:
- If the filament runs out, what should happen is that the MMU retracts the filament, moves the selector aside, and “ejects” the filament (sticking the end out into air) so you can remove the remaining piece. If that didn't happen, then something went wrong with the unload — possibly the tail end of the filament had a bend in it and got jammed while trying to retract, but you say the MMU was able to retract so perhaps that isn't the problem.
- In order to resume a print when the MMU (as opposed to the printer) thinks something is wrong but you've now corrected it, you need to push the right (not middle) button on the MMU. The middle button only does “recheck/retry” and the right button is “resume”.
My MMU has handled several filament run-outs or breaks, but I know other people have had trouble with the same steps. Sorry I don't have an “aha, this is exactly problem and solution” answer.
RE: Is there no way to recover a print with MMU2 after filament runs out?
By the time the filament end has been seen by the MMU, the filament is no longer in the MMU gear, so the MMU can't retract it by itself. I guess the extruder can extract and retract it a little ways, and perhaps it did jam in that process--I think the filament did indeed have a kink at the end.
Thanks for the tip about using the right button! I somehow never found the documentation that says what the buttons do in various situations.
Wow, thanks to you and using your info I was eventually able to get the printer to resume successfully!!
RE: Is there no way to recover a print with MMU2 after filament runs out?
Glad to hear it worked!
If you can catch the time when your filament's down to the last wrap of the spool, you can find the far end and cut off any kink that's there to make it more likely to unload properly.
RE: Is there no way to recover a print with MMU2 after filament runs out?
Time to build a gadget that sits between the spool and the MMU2 looking for the filament end, and operates a nipper to remove the last few inches!
Just need 5 of them--perhaps they can share a processor.
RE: Is there no way to recover a print with MMU2 after filament runs out?
Just been through this and found another approach. Shame prusa have not documented the correct procedure or even coded properly for the eventuality.
So as folks say when the FINDA drops the print stops an no retraction took place on my machine. Message said to press the knob to resume nozzle temperature. So knowing it wouldn't resume I detached the feed tube and hit the button to heat nozzle so I could remove the filament from the mmu2s to the extruder. Put tube back after this. Then got message mmu2s issue. So tried umpteen ways to load a new filament at this critical point. And this is the fail off the code. No matter what you do with control buttons the filament will only load to the FINDA and will not load to the extruder. So when you get the message has it loaded OK with options of, yes, filament not loaded, or no just answer yes. So even with no filament loaded it then goes ahead. Hit knob ASAP and pause print. Then unload the filament so it gets back in sync. Then load to nozzle, and then resume print. What a faf.
Same happened to me
This just happened to me - ran out of filament. It was retracted back to the mmu2 unit. Prompt me to remove the filament - which I couldn't do because it was in the ptfe from the spool to the mmu2. So I took out the ptfe and removed the filament.
Then, no matter what I tried, I couldn't get it to load the new filament to the hotend. It would only load it up to the finda and then park the filament.
RE: Is there no way to recover a print with MMU2 after filament runs out?
14Oct2023-This just happened to me, it ran out overnight and I got it back working.
New spool loaded up, pushed the new filament down PTFE#1 till it stopped, no combo of MMU button pushes worked. Would always just eject the new filament.
I pushed down on the PTFE release on the MMU side of MMU->Hotend tube, pulled the PTFE tube out of the MMU, then carefully pulled the old filament out of the hotend and tube. I then pushed the new filament out a bit past MMU, reconnected PTFE @ MMU threading the new filament into PTFE, and continued to push till the filament stopped at the hotend. Middle MMU button press, and it ejected it all the way up to the ball sensor in MMU, the MMU light went green, the display said to press the button, so I did on the main display, it reloaded the filament down, and asked if it loaded, I said yes and its back printing after it goo'ed out some from the nozzle that I quickly pulled away.
Hope this helps someone out there.
Jim
Printer: Prusa MK3S+ & MMU2S
Software: Fusion360 & Prusaslicer
OS: Win 7 Pro/CentOS 7
RE: Is there no way to recover a print with MMU2 after filament runs out?
Just to say this procedure worked for me as well. Glad to have been able to continue this 16hr print after my filament ran out at 80%...