Clogged nozzle beyond heatbreak
My dad has an XL, and was printing PETG.
One of the nozzles clogged and heat somehow melted the filament beyond the heat break. I don't know the exact parameters for this thermal runaway, but I can ask for details.
He was able to remove the nozzle, and ordered a replacement. However he is still trying to unclog the old one.
I've had this issue before on my old wanhao i3 after a "blob of death". But that I was able to mechanically clear the heat break tube because it is separate from the nozzle.
Any suggestions on how to solve this problem?
RE:
Remove everything except the nozzle with the tube, clamp it e.g. with a vise (careful not to damage the tube). Then heat it up with a heatgun until you can push the molten stuff through. Works best with long acupuncture needles and some 1.5mm wire, but you can get custom tools as well. You don't have to clean it 100%, it will chafe off with friction when printing.
Maybe your fan inlet is obstructed, but normally the firmware should track the heatbreak temps. Most likely you have set too much retraction for your material, which leads to the filament staying too soft/sticky. Another cause can be wrong idler tension. Or a deformed idler arm (when using some kind of enclosure, in this case it will from now on happen again and again).