The motor ground through a few cm of extrusion! it works!
Pretty soon, though the filament stalled and the screw ground down the filament. Feeding through by hand started it again, but it needed help.
I had to experiment a bit to get a consistent extrusion. Things that helped:
- I bought a cheap tap/die set and ran a die down the bolt thread to sharpen it
- tightening up the screws and springs pressing the filament onto the screw
- upping the temperature to 240 *really* helped. I think at 220 it's only just hot enough. I'm still not sure that thermistor reading is accurate.