Bed Mesh with Relative Reference Index

Bed Mesh with RELATIVE_REFERENCE_INDEX

These are the OLD instructions, for configuring a mesh using RELATIVE_REFERENCE_INDEX. If your Klipper install is new enough to support the new ZERO_REFERENCE_POSITION, you should follow the updated instructions here

Legacy, Trident, V2

Larger printers are also likely to need a bed mesh, but for different reasons.

While the thick beds themselves are usually quite flat, your gantry and frame will expand and warp a bit with chamber heat.
The extrusions with linear rails will actually bend slightly when heated due to differing rates of thermal expansion.

This often requires a bed mesh to compensate.

Setup

Because your mesh can change at different bed, chamber, and frame temperatures, it is generally recommended to generate a mesh before every print rather than using saved meshes.

All of the [bed_mesh] configuration options and explanations can be found in the Klipper docs.

Here is a sample configuration. You can copy & paste this into your printer.cfg, making sure to uncomment the appropriate mesh_min and mesh_max for your bed size.

The Switchwire stock configs already include this.

[bed_mesh]
speed: 300
horizontal_move_z: 10
##--------------------------------------------------------------------
##	Uncomment below for 250mm build
#mesh_min: 40, 40
#mesh_max: 210,210

##	Uncomment for 300mm build
#mesh_min: 40, 40
#mesh_max: 260,260

##	Uncomment for 350mm build
#mesh_min: 40, 40
#mesh_max: 310,310
##--------------------------------------------------------------------
fade_start: 0.6
fade_end: 10.0
probe_count: 5,5 # Values should be odd, so one point is directly at bed center
algorithm: bicubic
relative_reference_index: 12 # Update when changing probe_count, to ((x points * y points) - 1) / 2. (the center point)

Then, place BED_MESH_CALIBRATE in your PRINT_START macro, AFTER any homing and leveling routines like G28, G32, QUAD_GANTRY_LEVEL, and Z_TILT_ADJUST.
This will generate a mesh before every print.

Mesh Points

Generally a 5x5 grid is acceptable for even the largest Voron printer, but you can adjust the points as you see fit.

It is recommended to use odd values for numbers of points in X and Y, (such as 3x3, 5x5, or 7x7), so that there is always a probe point directly in the center of your bed.

Relative Reference Index (!)

The Switchwire should NOT use relative_reference_index.
The Legacy, Trident, and V2 SHOULD use relative_reference_index.

As the Legacy, Trident, and V2 use the probe as a relative and not absolute measurement device, it is critical that you have the relative_reference_index parameter. This value will change as you adjust your mesh size.

Your relative_reference_index should be set to ((x points * y points) - 1) / 2.

Examples:

3x3 mesh = 4
5x5 mesh = 12
7x7 mesh = 24
(etc)