Mk3S / MMU2S Extruder motor is HOT
So I finally got my MK3S / MMU2S printing properly (about 80% of the time). But I noticed that, ever since upgrading form my mk3, the new extruder motor gets very hot during printing. Too hot to touch, in fact.
After a couple of hours into printing, I'll start getting a lot of "MMU load failed", and I'm wondering if it has something to do with the extruder motor getting hot (maybe softening the filament as it passes through the bondtech gears?)
Has anyone else seen this? What could cause it?
RE: Mk3S / MMU2S Extruder motor is HOT
Symptoms (after three or four hours of successful printing):
- every third or fourth filament change requires handholding, with the tip of the filament chewed up, melted into a blob, or otherwise deformed and needing trimming.
- Random extrusion of huge blobs into the wipe tower, causing a crash. When this happens, the printer detects it, pauses / homes for about five seconds (not long enough to actually fix anything), then resumes printing, crashes again, rinse, repeat. Until I have to cancel my ten hour Benchy print after four hours of printing.
RE: Mk3S / MMU2S Extruder motor is HOT
How easy/hard is it to manually insert filament into the extruder? If it is hard, loosen the tension on the idler door. If that doesn't make it easier you may need to replace the door.
Even with the tension bolt barely biting the nut in the door I couldn't manually insert filament past the gears. I printed a new door to address potential issues with the IR flag and found it fits much looser than the one Prusa sent me and with it properly tensioned I can now insert and remove filament manually.
If there is too much tension on the gears that will make the motor work harder and run hotter.
RE: Mk3S / MMU2S Extruder motor is HOT
Thanks gnat. I saw the thingiverse link you posted in my other thread for the door. I printed it, but when I Tried to insert the bondtech gear shaft, it broke the printed part. I'll need to try again.
The replacement door is supposedly exactly the same as the prusa stock part, but with a longer "flag" at the top for the IR sensor. Are you saying that, in addition to the change int he IR sensor flag, there is a change in the mechanics of the retaining nut (so the tension on the door is reduced)? Like the nut has a deeper slot or something?
Could I accomplish the same thing with a longer M3 screw (I've got plenty of those lying around)?
RE: Mk3S / MMU2S Extruder motor is HOT
..Jus realized I forgot to answer your question. Is it "hard" to insert filament? I can't really say. It's certainly harder than on my old mk3, where the sensor was optical, and required no pressure at all. I don't really know what a "normal" amount of pressure would be here. Suffice it to say, the filament "bites" into the bondtech gear, even when the idler door is completely removed. I can turn the extruder motor shaft just by pushing the filament through.
RE: Mk3S / MMU2S Extruder motor is HOT
Thanks gnat. I saw the thingiverse link you posted in my other thread for the door. I printed it, but when I Tried to insert the bondtech gear shaft, it broke the printed part. I'll need to try again.
The replacement door is supposedly exactly the same as the prusa stock part, but with a longer "flag" at the top for the IR sensor. Are you saying that, in addition to the change int he IR sensor flag, there is a change in the mechanics of the retaining nut (so the tension on the door is reduced)? Like the nut has a deeper slot or something?
Could I accomplish the same thing with a longer M3 screw (I've got plenty of those lying around)?
No a longer bolt won't help as that would push the flag into the sensor.
I have no reason to doubt the rest of the door is identical. I think the difference is the printing. I'm not impressed with the quality of the Prusa supplied parts. Terrible ghosting, looks like Live Z could use some adjustment, etc...
Did you print it in PETG or PLA? The pin was indeed tough to get in (like had to use a tac hammer tough), but nothing broke. I printed it with Amazon PETG.
RE: Mk3S / MMU2S Extruder motor is HOT
Thanks gnat. I saw the thingiverse link you posted in my other thread for the door. I printed it, but when I Tried to insert the bondtech gear shaft, it broke the printed part. I'll need to try again.
The replacement door is supposedly exactly the same as the prusa stock part, but with a longer "flag" at the top for the IR sensor. Are you saying that, in addition to the change int he IR sensor flag, there is a change in the mechanics of the retaining nut (so the tension on the door is reduced)? Like the nut has a deeper slot or something?
Could I accomplish the same thing with a longer M3 screw (I've got plenty of those lying around)?
No a longer bolt won't help as that would push the flag into the sensor.
I have no reason to doubt the rest of the door is identical. I think the difference is the printing. I'm not impressed with the quality of the Prusa supplied parts. Terrible ghosting, looks like Live Z could use some adjustment, etc...
Did you print it in PETG or PLA? The pin was indeed tough to get in (like had to use a tac hammer tough), but nothing broke. I printed it with Amazon PETG.
Printed with Hatchbox PETG. but I'll give it another go.
RE: Mk3S / MMU2S Extruder motor is HOT
I noticed it today, too. It gets extremely hot. I don't have a laser thermometer but i guess its over 120C. I think its way to hot and could wear down the extrudermotor to fast. Maybe the messed up the voltage after a firmware update. I do hope they fix this because it really gives me anxiety.
