Overview:

The Z Belt Timing Pulley is located on the bottom side of the printer, and used to connect the Z axis leadscrew to the belt of the printer.

Removing the Z-Belt Timing Pulley
Step 1: Lock the Heatbed
On the display, lower the heatbed to its lowest position. Then use an H2.0 hex wrench to screw the three screws (originally used to secure the heatbed during shipping) into the three Z sliders, securing the sliders to the base. Finally, turn off the printer and disconnect the power.
Locking the heatbed is a key preparatory step. This action secures the relative positions of the three Z-axis lead screws, preventing accidental rotation or displacement caused by external force or the bed’s own weight when the belt is loosened. It maintains the bed’s reference plane, avoiding excessive tilt and ensuring the platform remains level.

Step 2: Remove the Glass Top Cover and Lay the Printer on Its Side
Remove the glass top cover before tilting the printer to prevent damage.
If you need to place the printer upside down, be sure to remove the display screen first to avoid damage. You can refer to the “Screen Replacement” guide for instructions on how to remove it.

Step 3: Remove the Z Pulley
Since the Z pulley screws are quite tight, hold the belt in place with your hand while loosening the pulley screws to prevent the pulley and screw from rotating together.
Remove the Z pulley cover. Then use a 2.0 mm hex wrench to loosen the tension screw and release the tension spring.
Remove the belt from the Z pulley, then insert a hex wrench under the pulley and pry the Z pulley out.

Installing the Z Pulley
Step 1: Install the Z Pulley
Align the slot of the new Z pulley with the bottom of the lead screw, install the Z pulley into place, then loop the Z belt back onto the pulley.
Reattach the tension spring into place, then install the pulley cover onto the pulley.
Hold the Z belt in place and tighten one screw using a 2.0 mm hex key.

Step 2: Unlock the Z-Axis Sliders
Place the printer upright, then use a 2.0 mm hex key to remove the three screws locking the Z-axis sliders.

Step 3: Tension the Z-Axis Belt and Tighten the Screw
Lay the printer on its side again, move the Z-axis belt back and forth to ensure smooth motion, then tighten the black screw.

Verifying Success
Connect the power cable and turn on the printer. Run the machine calibration process; if no errors appear, the replacement is complete.
If you encounter any problems, review the steps and check all connections before trying again. If the problem persists, please contact the Bambu Lab customer service team for further assistance.