inconsistent zoffset baby stepping on each print

[npm1]

Hia,
I have a Bltouch that's set up to probe the bed and home the z-axis, I have an ender 5 style 3d printer.

Everything works, however, when I've finally established the z offset for the g31 command, I tend to find that after probing the bed before a print, I still have to set the baby steps, I then find my self adding the baby step value to the g31 command, which just keeps growing, every time the print starts the nozzle is dug into the bed...

I have dual z axis, and will shortly add the antibacklash nuts.

I have also used the M500 command to save PID tuning, which you could see doesn't exist at the end of the config.g file (m500)...

Other wise its all good, I am thinking of adding a mechanical endstop for the bed so that I can set the 0 for the z axis, but main issue the fact that the zoffset is consistently being changed.
Please also review my config files for any error.

Kind Regards

Below are my files.

; homez.g
; called to home the Z axis
;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Tue Mar 16 2021 15:15:40 GMT+0000 (Greenwich Mean Time)
G91              ; relative positioning
G1 H2 Z25 F6000   ; lift Z relative to current position
G90              ; absolute positioning
G1 X150 Y150 F6000 ; go to first probe point
G30              ; home Z by probing the bed

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

; homey.g
; called to home the Y axis
;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Tue Mar 16 2021 15:15:40 GMT+0000 (Greenwich Mean Time)
G91               ; relative positioning
;M584 Y1 U4 P4; split y axis
G1 H2 Z25 F6000    ; lift Z relative to current position
G1 H1 Y-400 F500 ; move quickly to Y axis endstop and stop there (first pass)
G1 H2 Y10 F6000    ; go back a few mm

G1 H1 Y-400  F360  ; move slowly to Y axis endstop once more (second pass)
G1 H2 Z25 F6000   ; lower Z again
;G0 Y0.09                  ; fully align gantry
;M584 Y1:4 P3; join y axis

G90               ; absolute positioning

;M581 Y U S-1 T0 C0 ; Disable y triggers

; homex.g
; called to home the X axis
;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Tue Mar 16 2021 15:15:40 GMT+0000 (Greenwich Mean Time)
G91               ; relative positioning
G1 H2 Z25 F6000    ; lift Z relative to current position
G1 H1 X305 F1800 ; move quickly to X axis endstop and stop there (first pass)
;G1 H2 X-25 F6000    ; go back a few mm
G1 H1 X305 F360  ; move slowly to X axis endstop once more (second pass)
G1 H2 Z-5 F6000   ; lower Z again
G90               ; absolute positioning

;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Tue Mar 16 2021 15:15:40 GMT+0000 (Greenwich Mean Time)
G91                     ; relative positioning
;G1 H2 Z5 F6000          ; lift Z relative to current position
;G1 H1 X-305 Y-305 F1800 ; move quickly to X and Y axis endstops and stop there (first pass)
;G1 H2 X5 Y5 F6000       ; go back a few mm
;G1 H1 X-305 Y-305 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 Z5 F100             ; lift Z relative to current position
;G90                    ; absolute positioning

M98 P"homex.g"
M98 P"homey.g"
M98 P"homez.g"

; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Tue Mar 16 2021 15:15:40 GMT+0000 (Greenwich Mean Time)

; General preferences
G90                                             ; send absolute coordinates...
M83                                             ; ...but relative extruder moves
M550 P"NAZS"                                    ; set printer name

; Network
M552 S1                                         ; enable network
M586 P0 S1                                      ; enable HTTP
M586 P1 S0                                      ; disable FTP
M586 P2 S0                                      ; disable Telnet

; Drives
M569 P0 S0                                      ; physical drive 0 goes backwards
M569 P1 S0                                      ; physical drive 1 goes forwards
M569 P2 S0                                      ; physical drive 2 goes forwards
M569 P3 S1                                      ; physical drive 3 goes forwards
M569 P4 S0                                      ; physical drive 4 goes forwards

M584 X0 Y1:4 Z2 E3 U4 P3                            ; set drive mapping

M350 X64 Y64 Z64 E16 I1                  ; configure microstepping with interpolation
M92 X321.09 Y321.09 Z1481.48  E415.00          ; set steps per mm
M566 X1800.00 Y1800.00 Z7500.00 E120.00      ; set maximum instantaneous speed changes (mm/min)
M203 X12000.00 Y12000.00 Z180.00 E1200.00  ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z60.00 E250.00      ; set accelerations (mm/s^2)
M906 X1000 Y1000 Z1000 E800 I30             ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                  ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 S1                                ; set axis minima
M208 X285 Y300  Z300 S0                          ; set axis maxima

; Endstops
M574 X2 S1 P"xstop"                             ; configure active-high endstop for low end on X via pin xstop
M574 Y1 S1 P"ystop+e1stop"                           ; configure active-high endstop for low end on Y via pin ystop
;M574 U1 S1 P"e1stop" 
M574 Z1 S2                                      ; configure Z-probe endstop for low end on Z

; Z-Probe
M950 S0 C"exp.heater3"                          ; create servo pin 0 for BLTouch
M558 P9 C"^zprobe.in" H15 F120 T6000             ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X-29 Y0 Z4.15                           ; set Z probe trigger value, offset and trigger height
M557 X30:290 Y30:280 S40                        ; define mesh grid

; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B3950 ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0                           ; create bed heater output on bedheat and map it to sensor 0
M307 H0 B1 S1.00                                ; enable bang-bang mode for the bed heater and set PWM limit
M140 H0                                         ; map heated bed to heater 0
M143 H0 S120                                    ; set temperature limit for heater 0 to 120C
M308 S1 P"e0temp" Y"thermistor" T100000 B3950 ;25   ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1                           ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00                                ; disable bang-bang mode for heater  and set PWM limit
M143 H1 S280                                    ; set temperature limit for heater 1 to 280C

; Fans
M950 F0 C"fan0" Q500                            ; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1                                  ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500                            ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45                               ; set fan 1 value. Thermostatic control is turned on

; Tools
M563 P0 D0 H1 F0                                ; define tool 0
G10 P0 X0 Y0 Z0                                 ; set tool 0 axis offsets
G10 P0 R0 S0                                    ; set initial tool 0 active and standby temperatures to 0C

; Custom settings are not defined

M307 H0 A98.7 C77.1 D2.3 S1.00 V24.3 B0
M307 H1 A340.0 C140.0 D5.5 S1.00 V0.0 B0

; config-override.g file generated in response to M500 at 2021-03-26 16:45
; This is a system-generated file - do not edit
; Heater model parameters
M307 H0 A98.7 C77.1 D2.3 S1.00 V24.3 B0
M307 H1 A340.0 C140.0 D5.5 S1.00 V0.0 B0
; Workplace coordinates
G10 L2 P1 X0.00 Y0.00 Z0.00
G10 L2 P2 X0.00 Y0.00 Z0.00
G10 L2 P3 X0.00 Y0.00 Z0.00
G10 L2 P4 X0.00 Y0.00 Z0.00
G10 L2 P5 X0.00 Y0.00 Z0.00
G10 L2 P6 X0.00 Y0.00 Z0.00
G10 L2 P7 X0.00 Y0.00 Z0.00
G10 L2 P8 X0.00 Y0.00 Z0.00
G10 L2 P9 X0.00 Y0.00 Z0.00

; bed.g
; called to perform automatic bed compensation via G32
;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Tue Mar 16 2021 15:15:40 GMT+0000 (Greenwich Mean Time)
M561 ; clear any bed transform
G29 ; probe the bed and enable compensation

[OwenD]

@npm1
I may be reading what you're doing incorrectly, but for the sake of clarity.
If your current Z offset is 4.15mm and you find you have to baby step up by 0.15mm, then you should be subtracting the baby step amount, not adding it.
So your new setting will be 4.0mm.

[npm1]

@owend thanks for that response, that makes sense will be reviewing that shortly.

Was there any other findings in the gcode files

[OwenD]

@npm1
Nothing stands out except that your homex.g file has line commented out that would prevent it doing a fast/slow probe

;G1 H2 X-25 F6000    ; go back a few mm

[Phaedrux]

@npm1 said in inconsistent zoffset baby stepping on each print:

I have dual z axis,

Are the Z motors using the dual socket Z driver on the Duet2? Or are you using 2 independent drivers?

It's possible your z motors are getting out of sync and causing some tilt. If you have a spare driver you can use a driver for each motor and do tilt correction.

A trigger height of 4+mm on a bltouch is oddly large as well. When installed as directly by antclabs the trigger height should be ~2mm.