G29 is the central command for automatic bed levelling (ABL) or mesh levelling.

Usage

• To measure the bed
• To generate a height mesh
• To activate or deactivate the mesh
• To load or save stored meshes
• To apply Z corrections during printing
• The exact range of functions depends heavily on the firmware.

G29 in Marlin (very extensive)
Marlin supports many ABL methods:

• Bilinear mesh levelling
• UBL (Unified Bed Levelling)
• Linear ABL
• 3-point ABL
• Manual mesh levelling

G29 has different meanings depending on the mode.

Code example

Bilinear ABL

G29

Save mesh

G29 S1

Load mesh

G29 L1

Display mesh

G29 T

Activate UBL

G29 A

Klipper

Klipper does not use G29 for levelling. Instead:

• BED_MESH_CALIBRATE
• BED_MESH_PROFILE LOAD=default

BUT: In Klipper, it is possible to define macros that use G29 for calibration.

RepRapFirmware (RRF)

Perform mesh levelling
Result is saved in heightmap.csv

G29

Load mesh

G29 S1

Delete mesh

G29 S2

Translated with DeepL.com (free version)