Duet Bed Mesh Compensation incorrectly showing Z Offset ?

simonboydfoley

Hi All,
I have a BLTouch Z Probe with my Duet2Wifi for my CR10s printer.
I upgraded to the latest firmware, web server etc and I now get the following error when ever I do a mesh bed compensation;

G29
Warning: the height map has a substantial Z offset. Suggest use Z-probe to establish Z=0 datum, then re-probe the mesh.
49 points probed, min error -1.482, max error -1.175, mean -1.340, deviation 0.077

This is the procedure I normally follow.

(With Z offset set 0 G31 X-40 Y-10 Z0 P25 I1).

Home all axis.
disable axis limits. (M564 S0, G1 Z0)
level the nozzle to the bed and set actual Z (G92 Z0)
Work out the actual Z offset needed for the probe (G1 Z10,G30 S-1) x 5
work out the average offset and then set the offset in config.g
G31 X-40 Y-10 Z*** P25 I1 where *** = my calculated offset (positive decimal)
6). restart the Duet.
7). home and center.
8). Run Bed mesh compensation

I get the following graph from the Duet and the error message!

So it shows the bed as being "below Z=0"

so it looks like the duet is mistakenly applying the offset twice ??!?

It dose not seem to be affecting the print so it could just be an error in the software ?

If I do a mesh compensation after setting the Z to the actual Bed I get a more reasonable result ....

Phaedrux

Can you post your config.g and homing files so we can see what is being applied and when?

Have you seen this? https://duet3d.dozuki.com/Wiki/Using_mesh_bed_compensation

simonboydfoley

hi @Phaedrux , Thanks for the reply
to answer your questions, No I will read it now .... not sure it existed at the time I bought my Duet. I'll see if I have done something dumb.

[Edit: The only thing I have spotted that I don't do is cancel previous mesh bed levelling before I set the Z=0 and offset procedures, cant see that being relevant as the G92 z0 when the nozzle is on the bed sets the golden reference point ]
... I attach requested files

homeall.g
homedelta.g
homex.g
homey.g
homez.g
heightmap.csv
config.g

Veti

your home scripts need updating.

z=0 should be determined by the G30 command.
and you will need to create deploy and retractprobe scripts

examples from the configurator

; homeall.g
; called to home all axes
;
; generated by RepRapFirmware Configuration Tool v2.0.4 on Sun Sep 15 2019 21:01:39 GMT+0200 (Central European Summer Time)
G91 ; relative positioning
G1 Z5 F6000 S2 ; lift Z relative to current position
G1 S1 X-235 Y-215 F1800 ; move quickly to X and Y axis endstops and stop there (first pass)
G1 X5 Y5 F6000 ; go back a few mm
G1 S1 X-235 Y-215 F360 ; move slowly to X and Y axis endstops once more (second pass)
G90 ; absolute positioning
G1 X15 Y15 F6000 ; go to first bed probe point and home Z
G30 ; home Z by probing the bed

; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 S2 Z5 F100 ; lift Z relative to current position
;G90 ; absolute positioning

for the deployprobe see
https://betrue3d.dk/bltouch-on-duet-wifi-configuratio-and-usage/#deployretract

Veti

@chrishamm the configurator does not create the deploy and retract scripts at the moment.