M300 Z-Axis Lift Failure

Hello,

I’ve had an M300 down for some time now with a really strange Z-axis issue. When trying to lift the print bed up to the nozzle, the Z-motor will eventually seize and hold with a loud grinding/buzzing noise, failing to reach any higher.

When manually moving the print bed, this also happens - trying to move the bed up again can even start it sliding back down the screw instead, once the motor starts trying to move and loses holding torque.

Some more information,

  • There’s no consistent height that the lift fails at, and sometimes it can lift most of the way to the nozzle before stalling.
  • Jogging the motor triggers it more consistently than constant lifting.
  • With power removed, the bed slides back down the lead screw smoothly.
  • The problem started after a large Z-ABS print which came out with layer shifting in the Y-axis, but when I started the next print it couldn’t lift the bed to the nozzle.
  • The printer’s been unused for a few months now, but was in active (20+ hrs/week) use when the fault happened.

To try fixing it, I’ve:

  • Replaced the Z-axis motor
  • Tightened screws on the Z-axis shaft coupler
  • Changed the Z-axis shaft coupler
  • Lubricated the lead screw
  • Kept the ball screw bolts a little bit loose
  • Checked the lead screw for bends or damage
  • Cleaned out and relubricated the ball screw
  • Checked electrical connectors from the motor to the controller PCB

At this stage, all the mechanical parts seem to be in good shape, it’s just that the stepper is reaching stall torque sometimes? I’m not sure if there’s another component seizing somewhere, but the platform moves smoothly on the screw so I don’t think there is. As I’ve replaced the stepper motor as well, I don’t think it’s a simple Z-axis motor failure too.

Are there any other troubleshooting checks I can do to try to locate the problem? Either something I’ve missed is increasing the load, or a fault somewhere is limiting my torque. Could it be an issue in the controller or power supply, or maybe my replacement stepper was faulty? Does anybody have any suggestions?

Hello Stephen,

I see you have already had several attempts at fixing the device. Could you please provide some videos that illustrate the issues? This would be really helpful.

Best regards,
Karolina