Zprobe offset. Solved

[micktol]

I am trying to recalibrate my zprobe. Its was working fine untill today when I changed the mount. Now when I follow the instructions I cannot move the axis until I home them, but when I do I cannot move the z axis below zero. If I use m564 H0 I can follow the instructions until the G30 S-1 command which then has error x+y axis not homed.
If I put a rough estimate into the G31 Z command it does not appear to be taken into account and the head is always too high.

Here are the instructions I followed :

"Ensure that the Z offset in G31 in config.g is set to 0, these steps will be used to measure this actual offset. (send G31 Z0 to set it to 0).
Use the X and Y jog buttons to position the nozzle over the centre of the bed
Jog the nozzle down until it is just touching the bed or just gripping a sheet of paper.
Send command G92 Z0 to tell the firmware that the head is at Z=0
Jog the head up by 5 to 10mm
If the Z probe needs to be deployed, deploy it
Send command G30 S-1. The nozzle will descend or the bed rise until the probe triggers and the Z height at which the probe stopped will be reported. If you are using a nozzle-contact Z probe, the trigger height will be slightly negative. For any other type of Z probe where the probe triggers before the nozzle contacts the bed, it will be positive.
Repeat from step 5 two or three times to make sure that the trigger height is consistent.
In Duet Web Control, go to Settings -> System Editor and edit the config.g file. Set the Z parameter in the G31 command to the trigger height that was reported. Save the file."

Thanks.

[dc42]

@micktol said in Catch 22, Zprobe offset:

I am trying to recalibrate my zprobe. Its was working fine untill today when I changed the mount. Now when I follow the instructions I cannot move the axis until I home them, but when I do I cannot move the z axis below zero. If I use m564 H0 I can follow the instructions until the G30 S-1 command which then has error x+y axis not homed.

The G30 command requires X and Y to have been homed, regardless of the M564 setting. If for some reason you can't home X and/or Y yet, you can cheat by using a G92 command to tell the firmware the X and Y coordinates, for example G92 X0 Y0. That will flag the X and Y axes as having been homed.

[micktol]

Thank you for your reply David, I am able to get a value from the G30 S-1 command but it does not seem to be applied!
I have a corexy with sensorless homing on x+y and a pnp sensor on z. This is my config.g file:

; Drives
M569 P0 S1 ; Drive 0 goes forwards
M569 P1 S1 ; Drive 1 goes forwards
M569 P2 S1 ; Drive 2 goes forwards
M569 P3 S1 ; Drive 3 goes forwards
M569 P4 S0 ; Drive 4 goes forwards
M584 X0 Y1 Z2:4 E3 ;dual Z
M671 X-44:252 Y105:105 ; bed motor positions

M350 X16 Y16 Z16 I1
M350 E64 ; Configure microstepping with interpolation
M92 X81 Y81 Z400:400 E562 ; Set steps per mm
M566 X1800 Y1800 Z12 E1200 ; Set maximum instantaneous speed changes (mm/min)
M203 X6000 Y6000 Z180 E3600 ; Set maximum speeds (mm/min)
M201 X1000 Y1000 Z250 E1000 ; Set accelerations (mm/s^2)
M906 X1200 Y1200 Z1200 E1200 I30 ; Set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout
;Extruder
M207 S5.0 F2000 ;Retraction

; Axis Limits
M208 X0 Y0 Z0 S1 ; Set axis minima
M208 X195 Y210 Z200 S0 ; Set axis maxima

; Endstops
M574 X0 Y0 S0 ; Set active high endstops
M915 X Y S3 R0
; Z-Probe
M574 Z0 S2 ; Set endstops controlled by probe

M558 P8 I1 X0 Y0 Z1 ; Set Z probe type to switch and the dive height + speeds
G31 P600 X0 Y45 Z0.665 ; Set Z probe trigger value, offset and trigger height
M557 X10:185 Y45:175 S20 ; Define mesh grid

[dc42]

• What type of Z probe are you using? P600 in the G31 command is an unusual value these days.
• Is 0.665mm the Z probe trigger height that you measured?

[micktol]

David,
I have an inductive pnp sensor, I have tried setting it to type 5 and 8. The values it shows in dwc are 0 and 1000.
The 0.655 is the result of the G30 S-1 command.
What is strange is that it was working fine until I tried to recalibrate the height of the z probe.

[deckingman]

@micktol Are you by any chance using config_override.g and is there an M501 in your config.g. This would explain why changes to config.g seem not to be applied. Just a thought.........

[micktol]

Deckingman, I do not have any M501 commands but you made me think so I looked in my homeall.g and there is a M92 Z command which was overriding the G31 command. the M92 Z value was fine before I moved the probe!

Thanks Deckingman and David for your assistance.

[deckingman]

@micktol Glad you got it fixed. Can you edit the title of your first post and add "SOLVED" to the end of it.