Automating Z Offset Adjustments

Introduction#

Printing with diverse filament materials often necessitates Z offset adjustments for optimal bed adhesion and first layer squish. Manually executing these adjustments for each print job be inefficient and errors prone. This guide provides a comprehensive solution, detailing how to configure your Slicer to automatically incorporate necessary Z offset adjustments for each print job. Additionally, we will cover the modification of the PRINT_END macro to ensure the Z offset is reset to its default value upon print job completion, streamlining your printing process.

Prerequisites#

To utilize this guide, ensure you have the following:

• A 3D printer configured with Klipper firmware
• A compatible Slicer software that supports filament-specific start G-code, such as:
  • PrusaSlicer
  • SuperSlicer
  • OrcaSlicer
• Enable “Advanced” settings in your Slicer software to access the necessary configuration options.

Modifying the PRINT_END Macro#

The printer.cfg file should already contain a PRINT_END macro definition, as this is a standard configuration in Voron setups. If you require a template, refer to the callout section below. To modify the PRINT_END macro, append the following command to its end. If your macro utilizes the SAVE_GCODE_STATE and RESTORE_GCODE_STATE commands, ensure that the added command follows the RESTORE_GCODE_STATE command. This is crucial because RESTORE_GCODE_STATE also restores the saved G-code offset, which could result in incremental changes to the offset between print jobs, rather than resetting to the baseline offset.

    SET_GCODE_OFFSET Z=0

The SET_GCODE_OFFSET command effectively resets the positional offset on the Z-axis to zero, thereby ensuring that all subsequent G-Code commands will execute without any Z-axis offsets. This resets the baseline for Z-axis positioning, allowing subsequent print jobs to adjust from known starting point.

[gcode_macro PRINT_END]
gcode:
    # safe anti-stringing move coords
    {% set th = printer.toolhead %}
    {% set x_safe = th.position.x + 20 * (1 if th.axis_maximum.x - th.position.x > 20 else -1) %}
    {% set y_safe = th.position.y + 20 * (1 if th.axis_maximum.y - th.position.y > 20 else -1) %}
    {% set z_safe = [th.position.z + 2, th.axis_maximum.z]|min %}

    SAVE_GCODE_STATE NAME=STATE_PRINT_END

    M400                           ; wait for buffer to clear
    G92 E0                         ; zero the extruder
    G1 E-5.0 F1800                 ; retract filament

    TURN_OFF_HEATERS

    G90                                      ; absolute positioning
    G0 X{x_safe} Y{y_safe} Z{z_safe} F20000  ; move nozzle to remove stringing
    G0 X{th.axis_maximum.x//2} Y{th.axis_maximum.y - 2} F3600  ; park nozzle at rear
    M107                                     ; turn off fan

    BED_MESH_CLEAR

    # The purpose of the SAVE_GCODE_STATE/RESTORE_GCODE_STATE
    # command pair is to restore the printer's coordinate system
    # and speed settings since the commands above change them.
    # However, to prevent any accidental, unintentional toolhead
    # moves when restoring the state, explicitly set MOVE=0.
    RESTORE_GCODE_STATE NAME=STATE_PRINT_END MOVE=0

Configuring Filament Settings in Your Slicer#

This section uses PrusaSlicer as an example, but the process applies to other slicers as well.

Step 1: Access Custom G-Code#

In your Slicer, navigate to Filament Settings and select the Custom G-code entry (highlighted in blue in the screenshot below).

Step 2: Add Start G-Code#

SET_GCODE_OFFSET Z_ADJUST=0.3

Note that the SET_GCODE_OFFSET command is utilized again, this time with the Z_ADJUST parameter, differing from the Z parameter used in the PRINT_END macro. The key distinction between these parameters is that Z sets the positional offset to the specified value, whereas Z_ADJUST modifies the existing offset by adding or subtracting the given value. For instance, executing SET_GCODE_OFFSET Z=-0.2 followed by SET_GCODE_OFFSET Z_ADJUST=0.3 results in a cumulative positional offset of 0.1 for the Z axis. This highlights the importance of resetting the offset post-print to maintain the correct Z offset.

Verification Process#

To confirm that the adjustments are being applied correctly, perform the following steps:

1. Slice and initiate a new print job.

2. Observe the Z offset adjustment during the print job preparation phase. If the configuration is correct, the WebUI displays the desired Z offset in the Toolhead card, as shown in the screenshot below:

   

Further Reading#

• Klipper SET_GCODE_OFFSET documentation