Anycubic i3 Z-offset

Hi everyone,

I'm trying to finally resolve an issue that has plagued me for a long time regarding BLTouch and my Anycubic i3 Mega configuration. It seems no matter what I try I'm unable to get the Z-offset correct when using my BLTouch and "AUTO_BED_LEVELING_BILINEAR".

Some background:
* The BLTouch is installed and when retracted the needle is about 2-2.3mm above the nozzle height.
* I'm using this firmware: [github.com]
* Homing the printer brings the nozzle level with the bed.

The problem:
Whenever I print after a G29 levelling, the nozzle is always 4-5mm above the bed.

My levelling process:
* From a freshly flashed (and rebooted) printer
* Check the X gantry is level and homing correctly.
* Check that both Z-axis end stops are trigged at the same time
* Check that the nozzle is level with the bed when homed
* Manually level the bed with a piece of paper
* G28
* G29 (using the built in Special Menu automatic bed levelling)
* Save to EEPROM (Using the built in Special Menu)
* Move the nozzle to 5 cm above the centre of the bed
* M211 S0
* Manually jog the Z axis down until it catches a piece of paper
* M114 to get the Z-offset
* M851 Z with the result from the step above
* M500
* M501
* Reboot the printer
* Try and print

The only configuration changes I make to the Marlin config are:
*PID values for the hotend and heated bed
* Calibrated motor steps
* Offset settings for the probe:

#define X_PROBE_OFFSET_FROM_EXTRUDER -2  // X offset: -left  +right  [of the nozzle]
#define Y_PROBE_OFFSET_FROM_EXTRUDER -23  // Y offset: -front +behind [the nozzle]
#define Z_PROBE_OFFSET_FROM_EXTRUDER -2

Here's my start code:

G28 ;Home
;M501 ;Load bed levelling settings
M420 S1 ;Use bed levelling settings
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G1 Z5.0 F9000 ;move the head 5mm up for clearance
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
M117; Printing...
G5;

I've followed numerous guides, YouTube videos etc etc and still seem to have the same problem.

Edited 3 time(s). Last edit at 12/11/2020 09:37AM by ocampbell.

Make the restore Bed leveling Data line last on the list of startup G-Code.

M420 S1 ;Use bed leveling settings

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Computer Programmer / Electronics Technician

Quote
Roberts_Clif
Make the restore Bed leveling Data line last on the list of startup G-Code.

M420 S1 ;Use bed leveling settings

I'm afraid that made no difference.