Extruder Motor knocking backwards and forwards even when removed

Question

I was printing something using TPU via my Micro Swiss extruder and hot end on my Creality CR-10. Unfortunately the filament started squeezing out of the extruder because the nozzle was too close to the bed. I raised the Z-axis, kept the nozzle heated, and retracted filament. I had to go backwards and forwards a bit and ended tugging quite hard to finally get the filament removed.

When I loaded filament again (any type) I just got a knocking sound but no movement.

I removed the extruder motor and tried driving it again and it was just making a small step forwards and backwards continually while trying to extrude or retract.

I ordered a new extruder motor and fitted it today but found it was doing exactly the same. I am using the EZBoard Lite from TH3D and am worried that I might have damaged the stepper driver. Has anyone got any advice about what I can try next? It was printing fine, with well calibrated E-steps prior to the TPU filament problem, so I can't believe this is in any way related to a firmware/settings problem. I would appreciate any ideas, particularly if anyone knows whether a stepper driver can be replaced on the TH3D EZBoard Lite. Yes, of course I am heating the nozzle.

Answer 1

You've not noted if the Bowden tube was connected to the hot end during your testing process. Consider to disengage the Bowden tube at the hot end/carriage and command an extrusion. This will tell you which side of the tube should be checked.

If the stepper motor feeds filament with the tube disconnected, the problem is in the nozzle. Ensure to heat the nozzle prior to removing it. Exercise appropriate hot item caution. Alternatively, perform a nylon cold pull cleaning process, but that works best with nylon.

If the stepper motor does not feed filament with the tube disconnected, your focus on the stepper driver may be accurate, especially considering the replacement you've performed.