Mesh Bed compensation "not working enough"

Tryptamine

Hey guys,
I have quite an uneven printing surface (Maximum deviations: -0.368 / 0.520 mm)
This is like 4 layer heights between highest and lowest point of the bed.

I try to compensate for this with Mesh bed comp.
I see the mesh bed comp working, the z axis are moving in the correct directions to counteract the uneven surface when moving XY.
However, even with mesh bed comp on, the compensation is NOT ENOUGH to counteract the uneven surface.

Printing a first layer test using all of the buildplate, i see the following:
where i know the bed has a negative deviation, the layers do not stick. The needle hits the bed at the points of positive bed deviation.

How can this be?
Is my bed just too bad to be fully compensated for by mesh bed comp?

Algorithm of what I did:
Preheat to printing bed temp
G29

In config.g:

G31 P500 X28 Y8 Z0.35                             ; set Z probe trigger value, offset and trigger height
M557 X28:330 Y8:305 S40                            ; define mesh grid

homeall.g:

G91                     ; relative positioning
G1 H2 Z5 F18000         ; lift Z relative to current position
G1 H1 X-350 Y-310 F6000 ; move quickly to X or Y endstop and stop there (first pass)
G1 H1 X-350             ; home X axis
G1 H1 Y-310             ; home Y axis
G1 X5 Y5 F18000         ; go back a few mm
G1 H1 X-350 F300        ; move slowly to X axis endstop once more (second pass)
G1 H1 Y-310             ; then move slowly to Y axis endstop
G90                     ; absolute positioning
G1 X-13 Y6 F18000       ; go to first bed probe point and home Z
G30                     ; home Z by probing the bed

start gcode:

M561
G28 ;Home
G29 S1 P"heightmap.csv"


G1 X350 Y20 F18000
G1 Z0

G1 X332 Y20 F18000
G1 Z0.2
G1 X330

G1 X315 Z0.25 F120 E50
;G91
;G1 E-5 F1000
;G90
G1 X330 Z0.2 F400
G4 P3000
G1 Z0.1 F9000
G1 X300 Z0.35 F18000

G1 X150 Y150 F18000
;G91
;G1 E5 F1000
;G90

Anything wrong here?
Any explanation?
I could imagine the axis minima (0 for z) prevent the print head from following the printing surface because it'd have to move into negative z therefore. Otherwise, this is probably allowed in the firmware.

Many thanks in advance!

wummelfrosch

Hy,
what Kind of Z-Probe do you use ?

Phaedrux

Mesh compensation will allow going below the z0 point based on the heightmap, that's not a problem.

You should home Z with the probe at the center of the bed. It looks like you're currently homing at a corner?

Post your full config.g and the results of M122 please.