How to add M600 filament change to Klipper

Klipper has no built-in M600. Add a [pause_resume] section and a [gcode_macro M600] that pauses, parks the nozzle and unloads the filament. Then load the new spool with a LOAD_FILAMENT macro and send RESUME. All three macros are below, ready to paste into printer.cfg.

Does Klipper support M600?

Not out of the box. M600 is missing from Klipper’s list of supported G-code commands, so a print that reaches it logs Unknown command:"M600" and the print carries on. Klipper handles M600 once you define it as a [gcode_macro M600] that pauses through [pause_resume]. Klipper’s own sample-macros.cfg includes one.

Klipper’s G-code documentation says a less common command “may be possible to implement … with a custom gcode_macro config section.” The sample in config/sample-macros.cfg pauses, lifts, parks and retracts 50 mm. The version below adds a lift that stays inside your Z travel, a longer idle timeout, and a call to an unload macro.

How to add an M600 filament change macro in Klipper

1. Enable pause and resume. Add an empty [pause_resume] section to printer.cfg, unless Mainsail’s or Fluidd’s client config already includes one.
2. Add the load and unload macros. Paste LOAD_FILAMENT and UNLOAD_FILAMENT from the section below and set their lengths for your extruder.
3. Add the M600 macro. Paste the macro below and change the park position to a spot inside your bed.
4. Restart Klipper. Save the file and run FIRMWARE_RESTART, or use the save-and-restart button in your web interface.
5. Test it. Start a print and send M600 from the console. The nozzle should lift, park and pull the filament out.

[pause_resume]

[gcode_macro M600]
description: Pause, park and unload for a filament change
gcode:
    {% set X = params.X|default(10)|float %}          # park X: placeholder, use a spot inside your bed
    {% set Y = params.Y|default(10)|float %}          # park Y: placeholder
    {% set LIFT = params.Z|default(10)|float %}       # mm to raise above the print
    {% set pos = printer.gcode_move.gcode_position %}
    {% set origin = printer.gcode_move.homing_origin %}
    {% set max = printer.toolhead.axis_maximum %}
    {% set z_park = [pos.z + LIFT, max.z - origin.z]|min %}
    SAVE_GCODE_STATE NAME=M600_state
    PAUSE
    SET_IDLE_TIMEOUT TIMEOUT=3600                     # keep heaters and motors on for an hour
    G91
    G1 E-1 F2700                                      # pull back off the print
    G90
    G1 Z{z_park} F600
    G1 X{X} Y{Y} F6000
    UNLOAD_FILAMENT
    RESTORE_GCODE_STATE NAME=M600_state

Here is what each part does:

• PAUSE stops the print and saves the nozzle position. RESUME returns to it at recover_velocity, which Klipper’s configuration reference gives as “Default is 50.0 mm/s.”
• z_park lifts the nozzle by LIFT but never past position_max on Z. homing_origin accounts for any SET_GCODE_OFFSET, as in the END_PRINT macro.
• SAVE_GCODE_STATE and RESTORE_GCODE_STATE restore the slicer’s G90/G91 and M82/M83 modes before the print continues.
• UNLOAD_FILAMENT reads the hotend target when it runs, not when M600 starts. Klipper’s command templates page says a called macro “is evaluated when it is invoked”. Mid-print, that target is the print temperature.
• X, Y and Z can be overridden per call, for example M600 X=200 Y=10 Z=30. Klipper’s parameter names are “always in upper-case” and values are “always passed as strings”, hence the |float.

Shorter M600 with Mainsail or Fluidd client macros

If printer.cfg includes mainsail.cfg or fluidd.cfg, the PAUSE macro from those files already retracts and parks. Both files suggest this alias in their header comments:

[gcode_macro M600]
description: Filament change
gcode:
    PAUSE X=10 Y=10 Z_MIN=50    ; park front left, at least 50 mm above the bed
    UNLOAD_FILAMENT

Z_MIN=50 keeps the park height at least 50 mm above the bed. Their RESUME reheats the hotend if an idle timeout turned it off and pushes the 1 mm retract back before moving. Set variable_idle_timeout in their _CLIENT_VARIABLE macro to lengthen the timeout during a pause. Details are on the PAUSE and RESUME macros page.

Klipper load and unload filament macros

LOAD_FILAMENT and UNLOAD_FILAMENT heat the hotend if it is cold, then move the filament in or out in one command. Use these exact names, because Mainsail and KlipperScreen look for them to show their load and unload buttons.

[gcode_macro UNLOAD_FILAMENT]
description: Heat if needed, then pull the filament out
gcode:
    {% set target = printer.extruder.target %}
    {% set TEMP = params.TEMP|default(target if target >= 170 else 220)|float %}
    {% set LENGTH = params.LENGTH|default(50)|float %}   # placeholder: enough to clear the extruder gears
    {% set SPEED = params.SPEED|default(1500)|float %}   # mm/min
    M109 S{TEMP}
    SAVE_GCODE_STATE NAME=unload_state
    M83
    G1 E5 F300                                           # push first to soften the tip
    G1 E-{LENGTH} F{SPEED}
    RESTORE_GCODE_STATE NAME=unload_state

[gcode_macro LOAD_FILAMENT]
description: Heat if needed, then feed and purge
gcode:
    {% set target = printer.extruder.target %}
    {% set TEMP = params.TEMP|default(target if target >= 170 else 220)|float %}
    {% set LENGTH = params.LENGTH|default(40)|float %}   # placeholder: extruder gears to nozzle
    {% set PURGE = params.PURGE|default(25)|float %}     # mm pushed slowly through the nozzle
    {% set SPEED = params.SPEED|default(300)|float %}    # mm/min
    M109 S{TEMP}
    SAVE_GCODE_STATE NAME=load_state
    M83
    G1 E{LENGTH} F{SPEED}
    G1 E{PURGE} F150
    RESTORE_GCODE_STATE NAME=load_state

Notes on the values:

• Temperature. Pass TEMP= to choose it. Without it, the macros keep a current target of 170 C or more and otherwise heat to 220 C (a placeholder: set it for the filament you load most). Keeping the target matters mid-print, because a new one would carry into the rest of the print. The 170 matches min_extrude_temp, where Klipper says “The default is 170 Celsius.” Below it, an extruder move fails with Extrude below minimum temp.
• SPEED is in mm/min. KlipperScreen sends that unit: its buttons run LOAD_FILAMENT SPEED= with the selected mm/s speed multiplied by 60.
• Bowden printers need a LENGTH longer than the tube. Klipper rejects any extrude-only move longer than max_extrude_only_distance, and its reference says “The default is 50mm.” The error reads Extrude only move too long. Raise max_extrude_only_distance in [extruder] to a little more than your tube length.
• Heater left on. Run alone, either macro leaves the hotend hot. Send M104 S0 when you are done, or let the idle timeout turn it off.

How to change filament when M600 pauses the print

1. Wait for the unload. The nozzle parks and UNLOAD_FILAMENT pulls the filament back past the gears.
2. Swap the spool. Pull the old filament out, then push the new one in until it reaches the extruder gears.
3. Load and purge. Run LOAD_FILAMENT. If the old color still shows, purge again with LOAD_FILAMENT LENGTH=0 PURGE=20.
4. Clean the nozzle. Pull the purged string off the nozzle tip so it is not dragged into the print.
5. Resume. Send RESUME from the console or press Resume in your interface.

Do not leave the printer paused past the idle timeout. Klipper’s idle timer keeps running during a pause. When it expires (Klipper: “The default is 600 seconds”) it runs TURN_OFF_HEATERS and M84. Turning the motors off also clears Klipper’s homed state, so RESUME stops with Must home axis first.

The SET_IDLE_TIMEOUT TIMEOUT=3600 line in M600 gives you an hour. The new value stays until Klipper restarts or something changes it, so add SET_IDLE_TIMEOUT TIMEOUT=600 to your end-of-print macro.

Fixing “Macro LOAD_FILAMENT not found”

The message means no macro with that name is loaded. Klipper itself has no LOAD_FILAMENT or UNLOAD_FILAMENT command. Each interface reports the missing macro in its own way:

To fix it:

• Add the macros. Paste the two macros above into printer.cfg, or into a file that printer.cfg pulls in with [include macros.cfg]. A file that nothing includes is never loaded.
• Restart. Klipper reads macros only at startup, so run FIRMWARE_RESTART after saving.

Mainsail greys out its load and unload entries while the hotend is below min_extrude_temp. It makes an exception when the macro text contains M109, TEMPERATURE_WAIT or printer.extruder.can_extrude, since that macro heats for itself. The macros above contain M109, so they stay clickable on a cold printer.

Making the slicer or a runout sensor send M600

PrusaSlicer’s color change writes M600 into the G-code. Prusa’s knowledge base says the printer pauses “as soon as it reads the color change in the G-code (M600 command)”. Cura’s Filament Change post-processing script also writes M600. See manual color changes for the slicer side.

For a filament runout sensor, set runout_gcode: M600 and pause_on_runout: False in its [filament_switch_sensor] section, so the pause happens once, inside M600. With the default True, Klipper runs its own PAUSE first and M600 runs “after the PAUSE is complete.”