There are some cases when the automatic Z leveling fail during the calibration after several attempts.
This is because the Z height is not picked up correctly after it's set by the user.
The manual Z leveling can help to make the two head on the same level and the calibration will be successful.
- Heat up the extruders and unload the filament
- Keep the heads heated and wait if there is any filament oozing out from the nozzle. About 5 minutes.
- Clean both nozzle with a metal brush. Do not leave any filament residue on tip of the nozzle
- Turn off heating and move down the build plate about 10 cm
- Remove both fan assembly from the heads.
- Home the printer axis
- Turn off the printer. Move the left head to the middle of the build plate.
- Turn the front leveler knob to the right and make 2-3mm gap between the nozzle and the build plate.
- Loosen the left head heatbreak screws and let the head drop on the build plate. Move a little around - 2-3cm- to make sure the head is sitting softly on the build plate.
- Secure the heatbreak screws on the left head. Do not push down the head.
- Move away the left head and move the right head to the middle.
- Loosen the screws on the right heatbreak and let the nozzle drop on the build plate.
- Move around the right head - 2-3 cm - to make sure the head is sitting softly on the build plate.
- Secure the heatbreak screws on the right head. Do not push down the head.
- Move away the right head
- Mount the fan assembly on the heads.
- Turn on the printer and home the axis
- Do the full calibration. Now it has to check the Z height, and skip the Z calibration process.