Z-lift config for G29

[duetwifiuser]

Ahoi,

I just upgraded from 2.x to 3.3 and now I am wondering how to setup a Z lift for the G29 command.

Somehow this worked differently before, I remember the printhead diving down for each probe point, but now I get a 'Probe already triggered at start of probing move' error which makes sense since G29 requires the axis to be homed and so the probe is already triggered after finding Z.

I'm sure I missed something important when diff'ing my old config files against the new ones from the config tool but I can't figure out what =/

This is my current config.g:

; Configuration file for Duet WiFi (firmware version 3.3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.3.1 on Sun Aug 29 2021 15:53:02 GMT+0200 (Central European Summer Time)
 
; General preferences
G90                                            ; send absolute coordinates...
M83                                            ; ...but relative extruder moves
M550 P"Ender 3"                                ; set printer name
 
; Network
M552 S1                                        ; enable network
M587                  ; Configure access point. You can delete this line once connected
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 backwards
M569 P2 S1                                     ; physical drive 2 goes forwards
M569 P3 S0                                     ; physical drive 3 goes backwards
M584 X0 Y1 Z2 E3                               ; set drive mapping
M350 X16 Y16 Z16 E16 I1                        ; configure microstepping with interpolation
 
M591 P2 C"e0_stop" S1          ; filament monitor connected to E0_stop
M92 X80.00 Y80.00 Z400.00 E140.00              ; set steps per mm
M566 X1200.00 Y1200.00 Z24.00 E300.00     ; Set maximum instantaneous speed changes (mm/min)
M203 X30000.00 Y30000.00 Z300.00 E3600.00 ; Set maximum speeds (mm/min)
M201 X800.00 Y800.00 Z100.00 E5000.00     ; Set accelerations (mm/s^2)
 
M906 X800 Y800 Z800 E800 I30                   ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                        ; Set idle timeout
 
; Axis Limits
M208 X0 Y0 Z-1 S1                              ; set axis minima
M208 X220 Y220 Z250 S0                         ; set axis maxima
 
; Endstops
M574 X1 S1 P"xstop"                            ; configure active-high endstop for low end on X via pin xstop
M574 Y1 S1 P"ystop"                            ; configure active-high endstop for low end on Y via pin ystop
M574 Z1 S2                                     ; configure Z-probe endstop for high end on Z
 
; Z-Probe
M558 P5 C"^zprobe.in" H1 F120 T6000             ; set Z probe type to unmodulated and the dive height + speeds
G31 P500 X-42 Y2 Z0.0                          ; set Z probe trigger value, offset and trigger height
M557 X00:200 Y10:200 S20                       ; Define mesh grid
 
; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 C0 R4700 ; 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 B0 S1.00                               ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0                                        ; map heated bed to heater 0
M143 H0 S70                                    ; set temperature limit for heater 0 to 120C
M308 S1 P"e0temp" Y"thermistor" T100000 B4138 C0 R4700 ; 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 S260                                   ; 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 S0.3 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
 
M915 E S10 F0 R1 ; stall detection for extruder (S-value == offset, F1 == filtered, R1 == log - don't pause)
 
M302 P1 ; allow cold extrusion

Cheers!

[fcwilt]

@duetwifiuser

You say the probe is already triggered after finding Z

What exactly does that mean? What is the Z position at that point?

Thanks.

Frederick

[Phaedrux]

What kind of a probe is it?

[duetwifiuser]

It's an inductive Prusa PINDA knock-off.

The Z position at that point is reportet as 1.000 and visually correct.

M114
X:150.000 Y:110.000 Z:1.000 E:0.000 E0:-0.0 Count 12000 8800 400 Machine 150.000 110.000 1.000 Bed comp 0.000

I tried moving the printhead up with G1 H2 Z10 F6000 before running G29 and the printer moves towards XY(Z?) 0 which I guess would be the first probing point for the mesh before reporting ...
Error: Probe already triggered before probing move started
...and halting at:

M114
X:42.000 Y:8.000 Z:1.000 E:0.000 E0:-0.0 Count 3360 640 400 Machine 42.000 8.000 1.000 Bed comp 0.000

What I think I am missing is something like Marlin's Z_CLEARANCE_BETWEEN_PROBES offset by which the probe/printhead would raise itself between mesh points - I sadly can't see or remember how or why this worked with my old .g config files in the 2.x version before

[fcwilt]

@duetwifiuser

When a probe completes the Z position is supposed to be high enough that the probe is ready to do another probe.

However if the Z position is too low for the "first" probe then you can get a "already triggered" error.

So what is the Z position at the start of the probe that is failing?

Frederick

[duetwifiuser]

@fcwilt

That would be 10.000 as commanded via G1 H2 Z10 F6000.

Mesh grid is defined as M557 X00:200 Y10:200 S20 so I assume that the first probing point would be X:0, Y:10, Z:1 and its quite possible that my bed is angled/warped enough to trigger the probe before it reaches there.

This is why I am looking for a solution where the probe would stay at a safe distance to the bed while traveling between mesh points.

[fcwilt]

@duetwifiuser said in Z-lift config for G29:

@fcwilt

That would be 10.000 as commanded via G1 H2 Z10 F6000.

Mesh grid is defined as M557 X00:200 Y10:200 S20 so I assume that the first probing point would be X:0, Y:10, Z:1 and its quite possible that my bed is angled/warped enough to trigger the probe before it reaches there.

This is why I am looking for a solution where the probe would stay at a safe distance to the bed while traveling between mesh points.

Your G31 command in your config.g file says the Z Trigger Height setting is 0. Is that correct?

Normally that setting is a positive number. For example mine is 2.5.

When a probe is complete the Z position is the Dive Height (the H parameter in the M558 command) plus the Z Trigger Height (the Z parameter in the G31 command).

With your current parameters the Z position would be 1 + 0 - which doesn't allow much room for the bed to be out of level or uneven.

My dive height setting is 2 so the Z position would be 2 + 2.5 - which is plenty of room in most cases.

Frederick

[duetwifiuser]

@fcwilt

Thank you so much!

I feel really stupid now...

The Dive height was exactly what I was looking for - setting it to a generous 10 makes the printer behave exactly like it should/did before.

Somehow the zero got lost during copy'n pasting between old and new config.g - guess even BeyondCompare can't help with bad eyesight

Again, many thanks!

[fcwilt]

@duetwifiuser said in Z-lift config for G29:

@fcwilt

Thank you so much!

I feel really stupid now...

The Dive height was exactly what I was looking for - setting it to a generous 10 makes the printer behave exactly like it should/did before.

Somehow the zero got lost during copy'n pasting between old and new config.g - guess even BeyondCompare can't help with bad eyesight

Again, many thanks!

Glad I could help.

But what about the G31 Z parameter being 0 - is that truly the case. It is possible.

Frederick

[duetwifiuser]

@fcwilt

About the 0 trigger height:

That isn't really true, the correct value would be 0.84

I know its a bit weird, but since the bed isn't ideal, I actually prefer the Duet to think that the nozzle is basically on the bed when in reality it is floating ~1mm over it so I never run the risk of damaging the sheet should I command some move and forget to raise Z first.

The offset is then compensated for in the slicer...

[fcwilt]

@duetwifiuser said in Z-lift config for G29:

@fcwilt

About the 0 trigger height:

That isn't really true, the correct value would be 0.84

I know its a bit weird, but since the bed isn't ideal, I actually prefer the Duet to think that the nozzle is basically on the bed when in reality it is floating ~1mm over it so I never run the risk of damaging the sheet should I command some move and forget to raise Z first.

The offset is then compensated for in the slicer...

Well that is the first time I have heard of that approach - but I understand your concern.

You could also so it with the correct value in G31 then use a M290 command to set a Z offset.

Frederick

[duetwifiuser]

@fcwilt

You are of course right and I should really rather do it that way...

I'll keep it as is for the sake of consistency with my Marlin machines where I don't trust myself to always remember to apply M290 again after clearing the eeprom

Cheers!

[fcwilt]

@duetwifiuser said in Z-lift config for G29:

@fcwilt

You are of course right and I should really rather do it that way...

I'll keep it as is for the sake of consistency with my Marlin machines where I don't trust myself to always remember to apply M290 again after clearing the eeprom

Cheers!

You don't have to remember - you can execute it as part of your Z homing code so it will always take effect.

Frederick