Mesh Bed Levelling for LK4PRO & LK5PRO

For users of LONGER LK4PRO and LK5PRO FDM 3D printers, a BL-Touch automatic leveling sensor can help improve bed leveling accuracy and print consistency.

However, BL-Touch normally performs a new bed measurement before every print. This process takes extra time and may not be necessary if the printer remains in the same position and the print bed calibration does not change.

In this case, you can use the previously saved mesh data instead of creating a new mesh before every print. This guide explains how to enable saved mesh leveling and how to create a new mesh when recalibration is needed.

Why Use Saved Mesh Leveling?

A BL-Touch sensor creates a bed mesh by measuring multiple points on the print surface. This data records small height differences across the print bed. Normally, the printer creates a new mesh before each print. However, if:

The printer is not moved.
The print bed is not adjusted.
The calibration remains accurate.

Use the Previous Saved Mesh Before Printing

To use the previously saved mesh data, you need to modify the BL-Touch Start G-code in your slicing software. Replace your current BL-Touch Start G-code with the following code:

-- BL-TOUCH START GCODE --
G21 ; metric values
G90 ; absolute positioning
M82 ; set extruder to absolute mode
M107 ; start with the fan off
; confirm BL-touch safety
M280 P0 S160 ; BL-Touch Alarm release
G4 P100 ; Delay for BL-Touch homing
G28 X0 Y0 ; move X/Y to min endstops
G28 Z0 ; move Z to min endstops
; reconfirm BL-touch safety
M280 P0 S160 ; BL-Touch Alarm realease
G4 P100 ; Delay for BL-Touch
; bed leveling
M420 S1 Z5 ; enable bed leveling
; prepare hot-end
G92 E0 ; Reset Extruder
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position

G1 X0.1 Y150.0 Z0.3 F1500.0 E15 ; Draw the first line

G1 X0.4 Y150.0 Z0.3 F5000.0 ; Move to side a little

G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line

G92 E0 ; Reset Extruder

G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed

G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish
; -- end of BL-TOUCH START GCODE --

After this adjustment, the printer will load the saved mesh data and begin printing without performing a new bed measurement.

When Should You Create a New Bed Mesh?

Although saved mesh data can improve printing efficiency, a new calibration is recommended when:

The printer has been moved.
The print bed position has changed.
The leveling accuracy becomes inconsistent.
First-layer problems appear.

In these situations, create a new mesh calibration before printing.

How to Create a New Mesh Calibration File

Step 1: Create a G-code File

Open Notepad on your computer and paste the following G-code:

; bed leveling
G28 X0 Y0 ; move X/Y to min endstops
G28 Z0 ; move Z to min endstops
G29; Auto leveling
M500 ; save data of G29 and M420
M420 S1 ; enable bed leveling

Step 2: Save the File

Save the file as:

levelling.gcode

Important: Make sure the file is saved with the .gcode extension, not .txt.

Step 3: Copy the File to the microSD Card

Copy the levelling.gcode file to the printer's microSD card.
Insert the card into your LONGER LK4PRO or LK5PRO printer.

Step 4: Run the Calibration File

From the printer display:

Open the file list.
Select levelling.gcode.
Start the file.
Wait until the mesh measurement process is completed.

The printer will create and save the new bed mesh data.

Conclusion

Using saved mesh leveling data can reduce unnecessary calibration time on LONGER LK4PRO and LK5PRO 3D printers. When the printer and print bed remain stable, the saved BL-Touch mesh allows faster print preparation.

For situations where the printer has been moved or the bed condition has changed, simply run the leveling G-code file again to create a new calibration mesh. With proper mesh management, LONGER users can achieve more stable and efficient FDM printing performance.