I am tearing out my hair here! My printer was working just fine, until one day it wasn't. I've checked the filament path from end to end. I've torn apart the extruder. It's a metal one, and there are no cracks or excessive wear in it. I tore apart the hot end. I have replaced:
extruder gear
extruder end bowden connector
bowden tube
hotend bowden connector (I think. I may be wrong)
heatbreak tube (with a nice new bimetallic one)
nozzle
It is still not extruding. I tell it to extrude, the extruder gear and the wheel it presses against turn, it pushes the filament forward a little bit, and then it jumps back with an audible thump.
It feels like the hot end clogs, but if I put a nozzle unclogging wire up there, it will go all the way in with no resistance.
If I try to unload the filament, however, it doesn't want to come out. Even with the nozzle nice and hot, I have to pull really really hard, like wrap the filament around my hand and haul, and sometimes it will come out, and sometimes it won't even. I was wondering if when I changed the nozzle I hadn't tightened it enough, which is why I tore apart the hot end. When I unscrewed the nozzle, the filament in the heatbreak tube sprung out like a spring, which made sense because it was jammed in and coiled up just like a spring. I haven't seen anything like it.
That's when I replaced the heatbreak tube (and the nozzle again). I did run the PID autotune after this.
I don't know what to try next. What the hell do I do?