PLA Filament Doesn't feed, won't eject, after several hours
I have what I think may be a bad hot end on my MK3. PLA stops feeding after a couple of hours. The extruder starts skipping and adjusting the tension doesn't help. When I attempt to eject the filament, there is a deformation on the end of the filament that prevents it from ejecting. I have to take the extruder apart to get at the filament, cut the end, and then pull it out.
I see the same issues with ColorFabb nGen, but I can usually get the nGen out without disassembling the extruder.
Does anyone have an idea what may cause this?
Re: PLA Filament Doesn't feed, won't eject, after several hours
Do you have the Noctua fan mounted in the right direction?
Do you let the fan run until the hotend has cooled down after a print?
Re: PLA Filament Doesn't feed, won't eject, after several hours
The fan blows across the hot end, airflow from left to right, with the fan on the left and the exit on the right.
No, I do not allow the hot end to cool before ejecting. I eject with it at print temperature. If you wait for the hot end to cool the filament can't be removed by the extruder.
At the end of a print the fan runs until the hot end drops below 50 C. I have not changed this behavior and I do not shut off the printer until the hot end and bed are below 50 C.
Re: PLA Filament Doesn't feed, won't eject, after several hours
I am difficulty in ejecting too and the hot end is still at 215C. What I end up having to do is cutting the filament and putting the new filament on top.
Re: PLA Filament Doesn't feed, won't eject, after several hours
It has gotten a little better in the latest firmware, but because there is a little blob at the end of the filament, it can't get through the PTFE tube in the filament sensor cover. I found it easier to remove the sensor cover and eject, then pull the filament out the bottom of the tube
Re: PLA Filament Doesn't feed, won't eject, after several hours
In mine, the blob catches on the the printed extruder housing just below the PTFE tube, but it wouldn't go through the tube either. I had to remove that early on and have of course misplaced it.
The blob is running about 2.25 mm diameter. I can't see that anything should be that large in the hot end. Everything should be about 2 mm diameter at most. As the blob is at the end, I am starting to think either the heat bridge isn't machined correctly or the fin unit isn't assembled correctly. I have changed the nozzle in the event that was causing it, but the new nozzle doesn't help.
I am also starting to wonder if the new fan has something to do with it. Maybe the heat bridge isn't staying cool enough and the blob is caused by thermal creep. When I changed the thermistor on my MK2 I reassembled everything with thermal compound in all the joints; I am wondering if I should do the same with this hot end.
Re: PLA Filament Doesn't feed, won't eject, after several hours
Me too. If the printer has cooled down the unload function doesn't work the first try. I preheat and try to unload. It moves up then stops. Can't pull it out. I do a load filament and then the unload works perfectly. There's a hard lump in there somewhere.
Re: PLA Filament Doesn't feed, won't eject, after several hours
the latest firmware(rc4_b143) it now unloads a bit, them moves slowly after the first retraction. the firmware needs to be tweaked more for this to work properly. the previous firmware, it just retracts straight out in one shot, and there would sometime be strings when the filament is removed, which seems better than the filament blob stopping us from removing filament.
Re: PLA Filament Doesn't feed, won't eject, after several hours
My MK2 doesn't have this problem. Of course, most of the time I just push the tensioner away and yank the filament out by hand instead of ejecting, but I can't do that with the MK3. The MK2 doesn't leave the blob though.
Re: PLA Filament Doesn't feed, won't eject, after several hours
I can’t understand why the unloading process has two speeds either. The first step the stepper motor unloads the filament rather quickly but then it slows down allowing the heated end of the filament (the blob) to cool. Now the blob can’t get thru the printed part of the housing or the tube. The unloading should be done in one quick motion all the way out not allowing the blob to cool.
Re: PLA Filament Doesn't feed, won't eject, after several hours
I finally solved this problem in my MK3, at least when printing PLA. I haven't tried other materials yet. I suspect the heat break either was not machined to spec or wasn't installed correctly. I replaced the heat break with a titanium version and the printer is behaving normally. When I removed the old heat break, it looked like there was not much thermal paste installed between the heat break and the fin stack. I added a significant amount of high temperature thermal compound when I installed the new heat break.