---
tag: g425
title: Backlash Calibration
brief: Use a conductive object to calibrate XYZ backlash
author: marcio-ao

experimental: true
requires: CALIBRATION_GCODE
group: calibration

codes: [ G425 ]

notes:
  - |
    Requires `CALIBRATION_GCODE` and the following parameters:
    - `CALIBRATION_MEASUREMENT_RESOLUTION` determines the increments taken in mm when performing measurements.
    - `CALIBRATION_FEEDRATE_SLOW`, `CALIBRATION_FEEDRATE_FAST` and `CALIBRATION_FEEDRATE_TRAVEL` determine the speed of motion during the calibration.
    - `CALIBRATION_NOZZLE_TIP_HEIGHT` and `CALIBRATION_NOZZLE_OUTER_DIAMETER` refer to the conical part of the nozzle tip.
    - `CALIBRATION_REPORTING` enables `G425 V` for reporting of measurements.
    - `CALIBRATION_OBJECT_CENTER` and `CALIBRATION_OBJECT_DIMENSIONS` define the true location and dimensions of a cube/bolt/washer mounted on the bed.
    - `CALIBRATION_MEASURE_RIGHT`, `CALIBRATION_MEASURE_FRONT`, `CALIBRATION_MEASURE_LEFT` and `CALIBRATION_MEASURE_BACK` define the usable touch points. Comment out any sides which are unreachable by the probe. For best results, all four sides should be reachable.
    - `CALIBRATION_PIN`, `CALIBRATION_PIN_INVERTING`, `CALIBRATION_PIN_PULLDOWN` and `CALIBRATION_PIN_PULLUP` configure the pin used for calibration. For example, if the nozzle is grounded, the calibation cube would be connected to a digital input pin with a pull-up enabled.

parameters:
  -
    tag: B
    optional: true
    description: Perform calibration of backlash only.
  -
    tag: T
    optional: true
    description: Perform calibration of one toolhead only.
    values:
      -
        tag: index
        type: int
  -
    tag: V
    optional: true
    description: Probe cube and print position, error, backlash and hotend offset. (Requires `CALIBRATION_REPORTING`)
  -
    tag: U
    optional: true
    description: 'Uncertainty: how far to start probe away from the cube (mm)'
    values:
      -
        tag: linear
        type: float

examples:
  -
    pre: 'Check positional accuracy before calibration (Requires `CALIBRATION_REPORTING`):'
    code:
      - T1                  ; Switch to second nozzle
      - G425 V              ; Showing positional report for T1
      - T0                  ; Switch to first nozzle
      - G425 V              ; Showing positional report for T0
  -
    pre: 'Perform automatic calibration:'
    code:
      - G425                ; Perform full calibration sequence
      - M425 F1 S0          ; Enable backlash compensation at 100%
  -
    pre: 'Check positional accuracy after calibration (Requires `CALIBRATION_REPORTING`):'
    code:
      - T1                  ; Switch to second nozzle
      - G425 V              ; Validate by showing report for T1
      - T0                  ; Switch to first nozzle
      - G425 V              ; Validate by showing report for T0

---

This command performs an automatic calibration of backlash, positional errors, and nozzle offset by touching the nozzle to the sides of a bed-mounted, electrically-conductive object (_e.g.,_ a cube, washer or bolt).

This command measures backlash but doesn't enable backlash correction. Use [`M425`](/docs/gcode/M425.html) to enable backlash correction.