how to disable z stop in marlin

3 min read 17-01-2025

The Z-stop switch is a crucial safety feature on 3D printers, preventing the print head from crashing into the bed. However, there are situations where temporarily disabling it might be necessary, such as during bed leveling or specific advanced printing techniques. This guide will walk you through how to disable the Z-stop in Marlin firmware, emphasizing safety precautions and best practices. Remember, disabling the Z-stop increases the risk of damage to your printer. Proceed with caution.

Understanding the Risks

Before we proceed, it's critical to understand the potential consequences of disabling your Z-stop:

Head Crash: The most significant risk is the print head crashing into the bed. This can damage the nozzle, bed, and even other printer components.
Print Failure: Incorrect Z-height can lead to adhesion problems, layer shifting, and ultimately, a failed print.
Printer Damage: Severe crashes can damage the stepper motors or other mechanical parts.

Always prioritize safety. Only disable the Z-stop when absolutely necessary and under controlled conditions.

Methods to Disable the Z-Stop in Marlin

There are several ways to disable the Z-stop functionality in Marlin firmware, each with varying levels of complexity and permanence:

1. Comment Out the Z-Stop Code (Temporary Disable)

This is the simplest method for temporary disabling. You'll directly edit the Marlin configuration files. This is not a permanent solution; the Z-stop will be re-enabled when you re-flash the firmware with the original configuration.

Locate the Configuration File: Find your Marlin configuration files (usually Configuration.h and Configuration_adv.h). The exact location depends on your firmware setup.
Locate the Z-Stop Definitions: Search for lines related to #define Z_MIN_ENDSTOP_INVERTING and #define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP.
Comment Out the Lines: Add two forward slashes (//) at the beginning of these lines to comment them out. This effectively disables the Z-stop functionality. For example:
```
//#define Z_MIN_ENDSTOP_INVERTING true // Comment this line out
//#define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP true // Comment this line out
```
Compile and Upload: Compile the modified Marlin firmware and upload it to your printer's controller board.

Important Note: Remember to uncomment these lines (remove the //) when you're finished to re-enable the Z-stop.

2. Using M-Codes (Temporary Disable)

Marlin supports M-codes that can temporarily override certain functionalities. While not strictly "disabling" the Z-stop, it effectively ignores the switch during operation. This is also temporary.

Enable M-Code Support: Ensure your Marlin firmware has M-code support enabled.
Use the M851 Command: Use the M851 command to set the Z-probe offset. By setting a large negative offset, the printer will believe the nozzle is far above the bed, thus ignoring the Z-stop. Exercise extreme caution with this method. The exact value will depend on your setup. Start with a small negative value and test carefully. You might use a Gcode viewer to prepare a test file including M851 before running it on your printer.
Use the G28 command for homing.
Use a small offset for testing: A small negative value can help to calibrate the Z-height.

3. Modifying the Marlin Configuration (Permanent Disable - NOT RECOMMENDED)

Modifying the configuration to permanently remove Z-stop functionality is strongly discouraged. It significantly reduces the safety of your printer. If you choose to do this, you assume all responsibility for any resulting damage. This is generally done by removing all references to the Z-stop within the configuration files. This is a permanent change and requires a complete re-flash of the firmware.

Safe Practices When Disabling Z-Stop

Manual Control: Always manually control the Z-axis movement when the Z-stop is disabled. Avoid automated homing routines.
Slow Movements: Move the Z-axis very slowly to prevent sudden crashes.
Visual Monitoring: Keep a close eye on the print head's position to avoid collisions.
Low Heights: Work at low Z-heights to minimize potential damage.
Backup your files: Always make a backup of your configuration files before making any changes.
Test with a small offset before attempting large changes.

Conclusion

Disabling the Z-stop in Marlin is a powerful but risky procedure. Use it only when absolutely necessary and always prioritize safety. Remember to re-enable the Z-stop after completing your task. If unsure, seek guidance from experienced 3D printer users or consult the Marlin documentation for your specific firmware version.