Any help troubleshooting why the Z axis belt slips?

I’m having an issue where my Z axis belt slips as shown in the attached video. It typically happens when the spindle is raised to the top of the Z axis when running the homing sequence.
Today I had a similar issue but now lower on the Z axis, stopping the spindle from traveling up or down.

Some troubleshooting I’ve attempted:

  • Checked the Z axis belt, no worn teeth and both gears for the belt appear in good condition/no wear
  • Attempted to adjust the Z motor to insure the belt was tight
  • adjusted the fly wheels on the Z gantry (where spindle moves up and down)

Was running the machine in fairly cold weather, in my garage but the door was open, if that might affect the performance. Or I’m thinking I need to replace the Z belt. Any advice would be appreciated.

Did you tighten all the allen screws on the motor couplers?

everything is tight

Put a mark across the top of the pulley and shaft and check to see if that is where it is slipping.

Hard to tell from that video, but it could be an issue with the wiring/connections for the Z stepper. Can you check and reseat all connections from the motor to the controller?