During calibration, mesh bed leveling, or before a print, it is crucial for the printer firmware to determine the print head and heatbed position. This is done through the homing process, where the print axes move to a known reference position, called home.
The MK3.5 firmware uses the SuperPINDA probe readings of their distance to the steel sheet. In case of an issue with the readings and the value difference between them, the printer will show the message "Failed to home the extruder in Z-axis".
Error name: Homing Error Z
Error code: #23301
The error might indicate an issue with the SuperPINDA probe. Its cable can be damaged or disconnected. A mechanical issue on the Z-axis might also trigger this error.
Follow the steps in the following article: PINDA/SuperPINDA testing.
Check that the SuperPINDA probe wires are not visibly broken. Also, ensure everything is connected to the xBuddy mainboard, inside its case. Loosen the four screws securing the cover, and open the cover to reveal the board.
Check that all the connectors are secure in their sockets. Though unlikely, rough shipping or handling could have shaken the SuperPINDA cables loose.
Ensure that the Z-axis can move smoothly. With the printer switched off, check the Z-axis and trapezoidal nut assembly:
Double-check the orientation of the trapezoid nuts, assembled on the Z-axis motor leadscrews. A section of their threads should be inside the printed part, not protruding up from the printed part. The highest point should be the M3 bolts securing the trapezoid nuts.
Ensure nothing is touching the printer components during the Z-axis range of movement, for example, zip ties from the cable bundles.
If the previous check did not solve the issue, check the extruder and hotend assembly from the linked dedicated guide.