---
tag: g034b
title: Mechanical Gantry Calibration
brief: Modern replacement for Průša's TMC_Z_CALIBRATION
author: thisiskeithb

group: calibration
since: 2.0.4
requires: MECHANICAL_GANTRY_CALIBRATION

codes: [ G34 ]
related: [ M422, M906, M907, M915 ]

parameters:

- tag: S
  optional: true
  description: "Current value to use for the raise move.<br/>(Default: `GANTRY_CALIBRATION_CURRENT`)"
  values:
  - unit: mA
    type: int

- tag: Z
  optional: true
  description: "Extra distance past `Z_MAX_POS` to move the Z axis.<br/>(Default: `GANTRY_CALIBRATION_EXTRA_HEIGHT`)"
  values:
  - unit: linear
    type: float

videos:
- 3jAFQdTk8iw

example:
- pre: 'Mechanical gantry calibration:'
  code: G34

---

This command is used to align the ends of the X gantry. See the [video demonstration](//youtu.be/3jAFQdTk8iw?t=684) below.

- The carriage moves to `GANTRY_CALIBRATION_SAFE_POSITION`, also called the "pounce" position.
- If possible, the Z stepper current is reduced to the value specified by `S` (or `GANTRY_CALIBRATION_CURRENT`) to prevent damage to steppers and other parts. *The reduced current should be just high enough to move the Z axis when not blocked.*
- The Z axis is jogged past the Z limit, only as far as the specified `Z` distance (or `GANTRY_CALIBRATION_EXTRA_HEIGHT`) at the `GANTRY_CALIBRATION_FEEDRATE`.
- The Z axis is moved back to the working area (also at `GANTRY_CALIBRATION_FEEDRATE`).
- Stepper current is restored back to normal.
- Finally the machine is re-homed, according to `GANTRY_CALIBRATION_COMMANDS_POST`.
