Possible motor issue?
Hi everyone,
I’m hoping someone can help confirm my suspicion, because this really doesn’t feel normal.
My MK3S extruder has been showing intermittent loss of pushing force, but the behavior of the extruder stepper motor itself is what worries me most. Sometimes the motor stalls completely during extrusion or filament loading, and I need to manually rotate the motor shaft slightly to get it moving again.
What seems especially wrong is this: even when the motor is completely removed from the printer and fully unplugged, it is extremely hard to rotate by hand. It doesn’t feel like normal stepper “cogging” — it sometimes almost feels seized and requires a lot of force to turn.
Because of this, the extruder can slip easily and I can even hold the filament with my fingers while it skips, which obviously shouldn’t happen. When filament feeds with no resistance, it may work for a while, but any additional load causes stalling or skipping.
This happens even without MMU2S connected, although the issue becomes more obvious when feeding through the MMU. I’ve already disassembled the extruder, cleaned the gears, and checked idler tension, and mechanically everything else seems fine.
At this point I strongly suspect a failing extruder stepper motor (internal mechanical issue or damaged bearings) rather than firmware or settings.
Has anyone encountered a stepper motor on MK3S that was abnormally hard to rotate when unplugged and caused intermittent stalling?
Thanks a lot for any insight or experience
It looks like you have already done this but for anyone else with similar problems:
Disconnect everything from the motor and try turning it by hand - you should feel the steps but nothing else, no sticky spots and no grating. If you do feel something one of the internal bearings on the rotor has probably failed.
Don't try to replace the bearing, replace the motor.
Cheerio,