eddy_livecalibrate

Live Z-center calibration for Klipper with an eddy-current probe (e.g. BTT Eddy). A single macro, CALIBRATE_Z_CENTER, that probes two points just before a print and sets a live gcode Z offset from their difference — so your first layer tracks gantry/frame thermal drift instead of relying on one cold calibration.

How it works

It probes two spots and applies:

z_offset = z_a - z_b + z_adjust

Term	Meaning
z_a	Probe trigger height at point A (reference, near gantry)
z_b	Probe trigger height at point B (bed center)
z_adjust	Fixed fine-tune term for your bed/nozzle (you calibrate this)

The A−B difference captures how far the center has moved relative to the reference between prints (thermal expansion, bed sag), and z_adjust dials in the absolute first-layer height. The result is applied with SET_GCODE_OFFSET Z=... MOVE=0.

The macro is split into three parts because Klipper needs a command to complete before printer.probe.last_z_result is readable — so each PROBE hands off to the next macro:

1. CALIBRATE_Z_CENTER — probes A, then calls…
2. _CALIBRATE_Z_SAVE_A — stores z_a, probes B, then calls…
3. _CALIBRATE_Z_APPLY — computes and applies the offset.

Requirements

• Klipper with a probe exposing printer.probe.last_z_result after a bare PROBE (eddy-current probes like BTT Eddy do).
• The printer must be homed and any gantry leveling (QGL / Z_TILT) done before calling this, or the two probe points aren't comparable.

Install

Copy eddy_livecalibrate.cfg into your config directory and include it:

# printer.cfg
[include eddy_livecalibrate.cfg]

Restart Klipper (FIRMWARE_RESTART).

Usage

Call once in your print-start sequence, after homing + leveling + mesh:

CALIBRATE_Z_CENTER

Parameters

All optional; defaults are for a ~350 mm Voron-style bed — change them for your machine:

Param	Default	Meaning
POS_A_X POS_A_Y	175, 295	Reference probe point
POS_B_X POS_B_Y	175, 175	Bed-center probe point
PROBE_Z	3	Travel / probe-start Z
Z_ADJUST	-0.815	Fine-tune offset (calibrate this)

Example:

CALIBRATE_Z_CENTER POS_A_X=175 POS_A_Y=295 POS_B_X=175 POS_B_Y=175 Z_ADJUST=-0.80

Tuning Z_ADJUST

• Positive → nozzle farther from bed (higher first layer).
• Negative → nozzle closer to bed (lower first layer).

Start from your known-good single-point Z offset and adjust in ~0.02 mm steps using a first-layer test print.

The default Z_ADJUST = -0.815 is specific to the original machine. It is not universal — calibrate your own before relying on it.

License

GPLv3 — see LICENSE. (Matches Klipper's own license.)