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Calibration: Toolhead

MMU_CALIBRATE_TOOLHEAD measures the toolhead geometry Happy Hare needs for accurate loading/unloading and purge-volume calculations: toolhead_extruder_to_nozzle, toolhead_sensor_to_nozzle, toolhead_entry_to_extruder, and toolhead_residual_filament. The full step-by-step procedure - cold pull, CLEAN=1, DIRTY=1, CUT=1, with worked transcripts for each - lives on Blobbing and Stringing, since getting these dimensions right is one of the most effective ways to reduce blobbing and stringing at toolchanges. This page covers whether you need to run it at all, and where it fits alongside the other calibration steps.

Do you need to run it?

It's optional if you picked a known toolhead/extruder combination during install. menuconfig's Toolhead screen (see Getting Started with Box Turtle: Picking a toolhead) lets you choose your actual hotend/extruder combo from a list of community-measured values, pre-filling toolhead_extruder_to_nozzle and toolhead_residual_filament for you. If your exact combination is listed, this is a genuinely good starting point - accurate enough for most users without ever running the calibration command.

It's effectively required for an unknown or heavily modified toolhead. If your combo isn't listed - or you picked "Other/Unknown" - Happy Hare falls back to generic dimensions that may be noticeably off for your specific hardware. MMU_CALIBRATE_TOOLHEAD is how you replace that guess with a real measurement.

It hard-requires a toolhead sensor. Unlike every other calibration command on this site, there's no manual fallback here - the command raises an error and refuses to run at all without one. If you don't have a toolhead sensor, your only path to more accurate values is hand- measuring and editing the four toolhead_* parameters directly (see Config Parameters for their meaning), not a guided command.

Where it fits in the order

Toolhead calibration is independent of the other steps on Calibration - it doesn't depend on selector, gear, encoder, or bowden calibration, and none of them depend on it. Run it whenever convenient, and re-run it any time you change toolhead hardware (a new hotend, a different nozzle length) without needing to redo anything else.

See also