cnc z probe problem

Ian 0

Hi, I have a home-built cnc machine (mpcnc) with a Duet2 wifi card running Reprap. I am having great difficulty in setting up a simple Z height probe. I have attached the probe - a crocodile clip to go on the tool and a flat metal plate to sit on the workpiece to the Z-Probe connector with one part going to the Z_PROBE_IN and the other to 3.3V. I have tried to define the probe by 'M558 K0 P4 C"zprobe.in" H5 F500 T500' but when I do a G31, I get an error saying 'ERROR:G31:Invalid Probe Index' and I get the same error with G38.2. I also tried 'M558 K0 P4 C"Z_PROBE_IN" H5 F500 T500', and tried changing the C".... parameter to C4".... , all with the same result.
I have been messing with this for over a year now, on and off, as my wife has been very ill so time has been limited but it is really getting to me now and I hope someone might be able to help. Thanks

Nightowl

@ian-0
I appreciate this must becoming frustrating for you, but it would help if you could give us a bit more information, particularly your config.g file.

If you click the </> icon above, then paste the entire text of your config.g file, that would be a great start.

Thank you.

Ian 0

@nightowl ```
; Configuration file for Duet
; executed by the firmware on start-up
; WorkBee Firmware Version 1.1

global systemSettingsVersion={1.2}

M575 P1 S1 B57600

; Configuration files
M98 P"config-network.g"
M98 P"config-drives.g"
M98 P"config-axes.g"
M98 P"config-axes-limits.g"
M98 P"config-axes-calibration.g"
M98 P"config-axes-endstops.g"
M98 P"config-probe.g"
M98 P"config-spindle.g"
M98 P"config-laser.g"

; Other Settings
M453 ; Put the machine into CNC Modes
G90 ; Set absolute coordinates
M140 H-1 ; Disable heated bed
M564 S1 H1 ; Disable jog commands when not homed
M911 S21.0 R23 P"G91 G1 Z3 F1000" ; Configure power loss resume

; User Configuration files
M98 P"config-user-settings.g"

I did do a bit more trawling around the net and tried changing the config-probe again to :
M558 K1 P5 C"^zprobe" H5 F500 T500     but this still gives me an error of :
g31
Error: G31: Invalid Z probe index    when I run the G31

Storm

Depending on your version of RRF, I don't think P4 is supported anymore.
Try P8 like below

M558 K0 P8 C"zprobe.in" H5 F500 T500

You might want to slow your probe speed down a bit as well but that's personal preference.

Ian 0

@storm Thanks, That appears to be finding a probe but whether the touch plate is touched or not gives me the same answer to G31 - g31
Z probe 0: current reading 1000, threshold 500, trigger height 0.700, offsets X0.0 Y0.0
Should that be the case? I assumed I should get a different reading.

Ian 0

@storm My Reprap version is 3.3

Ian 0

A thought I had is, the two probe wires are currently connected to Z_PROBE_IN and 3.3v on the probe port - should they be connected to Z_PROBE_IN and Ground with the pullup resistor activated? I also can't remember where I set the thickness of the touch plate to 0.7mm and I can't see it in any of the system files.... any idea? Thanks.

Storm

@ian-0 Yes you should be getting a different reading.
For me I get a Probe status of 0 when it's not touching and 1000 when it hits the plate. If you are getting 1000 when it's in the air then you may need to invert the pin with a !

My z probe input is inverted and looks like

M558 K0 P8 C"!io8.in" H10 F120 T3000

and my G31 output is

Z probe 0: current reading 0, threshold 500, trigger height 10.000, offsets X0.0 Y0.0 U0.0

The thickness of the touch plate is dealt with during the probing sequence. I have a Macro that I run for Z probing which is a file called Z-Probe.g in the Macros directory, the code for which is below

; Z probe.g
; called to find workpiece Z via G38.2
;

var ProbeThickness = 9;
var CoordSystem	= 20;
 
; If the printer hasn't been homed, home it
if !move.axes[0].homed || !move.axes[1].homed || !move.axes[2].homed
	G28
 
; Display message without time-out and allow to position the bit
M291 T-1 S3 X1 Y1 Z1 P"Make sure the bit is positioned above the Z probe" R"Touch probe"

; With bit above center of probe
G91									; relative positioning
 
; Probe Z component
G38.2 Z{move.axes[2].userPosition - (var.ProbeThickness + 2.25)}	; seek until the probe circuit is closed
G0 Z5									; rapid move Z axis 5 mm
 
G10 P1 L{var.CoordSystem} Z{var.ProbeThickness + 5}			; store relative probe offset for coordinates system 1
 
G90									; Absolute positioning

Ian 0

@storm Thanks, I'll try that.

Ian 0

@ian-0 I changed the probe file to invert the pin and it did give me 'current reading 0"' - unfortunately it also gave me 0 when the crocodile clip was clipped to the plate! I dabbed a multimeter round the pins of the Z-Probe port and I got 4.65v on the Z_PROBE_IN pin, 4.3v on the GND pin, )v on the Z_PROBE_MOD pin, and 3.3v on the 3.3v pin. I'm beginning to wonder whether the probe port is duff... can I put the probe onto another input - say E6_STOP on the expansion header and then to either 3.3v or GND on the same port? Should that then work as M558 K0 P8 C"!E6_STOP" H10 F120 T3000? Thanks.

Ian 0

@ian-0 That should have been 0v on the Z_PROBE_MOD pin..... dohhh!

Ian 0

@ian-0 I have now - finally - got it sorted.. I am now using the E6STOP input on the expansion port connector and GND pin with pullup and inversion applied. M558 K0 P8 C"!^exp.E6_STOP" H0.7 F120 T3000 . Thanks for all your help.