duet wifi + 3dtouch: offset keeps going up at each probe

[janko]

I have a weird problem here with my touch sensor: each probe keeps going up higher and higher in the offset. I am breaking my head over it, but can't figure out what is going on.

First of: what i mean:
Stopped at height 3.408 mm
Stopped at height 3.948 mm
Stopped at height 4.191 mm
Stopped at height 4.503 mm
Stopped at height 4.589 mm
Stopped at height 4.738 mm

Probing is done at x110 y 110 Z10 with G30 S-1 command

Parts out of the config.g:

; Z-Probe
; BLTouch - Heaters
M307 H7 A-1 C-1 D-1 ; Disable the 7th Heater to free up PWM channel 5 on the Duex board.
M558 P9 X0 Y0 Z1 H5 F500 T2000 A1 R0.5
G31 X24 Y-2 Z0 P10

homez.g (don't think that G30 uses this? but still, bytes are free
G91
G1 Z10 S2 F200
G30 ; Do a single probe to home our Z axis
G90 ; Make sure we are in absolute mode
G1 Z10 F6000 ; Rapidly move the Z axis to Z=10.

bed.g:
M561 ; clear any bed transform
; Probe the bed at 4 points
G30 P0 X15 Y15 H0 Z-99999
G30 P1 X15 Y195 H0 Z-99999
G30 P2 X195 Y195 H0 Z-99999
G30 P3 X195 Y15 H0 Z-99999 S

The touchsensor is a 3dtouch (i know, not as accurate as a bltouch, but this is a bit weird what is going on ), wired on the probe-in port for the signal, with a resistor between ground and signal wire.

If anyone has any idea: i would be thankful, I'm kinda stuck at the moment.

[janko]

To make sure it's not a firmwarethingie: upgraded just to 2.0(RTOS)RC6 (2018-05-29b4)

results now:
17:50:13G30 S-1
Stopped at height 4.403 mm
17:50:09G0 Z10
17:50:01G30 S-1
Stopped at height 4.257 mm
17:49:57G0 Z10
17:49:47G30 S-1
Stopped at height 4.202 mm
17:49:43G0 Z10
17:49:29G30 S-1
Stopped at height 3.736 mm
17:49:24G0 Z10
17:48:52G30 S-1
Stopped at height 3.542 mm
17:48:47G0 Z10
17:48:42G30 S-1
Stopped at height 2.804 mm
17:48:37G0 Z10
17:48:23G30 S-1
Stopped at height -0.107 mm
17:48:11G28 Z

[Scachi]

I had this problem with one BLTouch. It started to do so after I managed to drive the BLTouch hard into the bed (missed some wiring after modifying my printer), I think that damaged my probe.

After replacing it with a new BLTouch the problem was gone, not sure if there was another problem that may have caused this as I was still modifying my printer when I ordered the new one and tested it after finishing it with the new BLtouch only - So I can't guarantee that a new probe will fix your problem.

[janko]

18:53:47G30 S-1
Stopped at height -0.762 mm
18:53:43G0 Z5
18:53:35G30 S-1
Stopped at height -0.647 mm
18:53:30G0 Z5
18:53:26G30 S-1
Stopped at height -0.641 mm
18:53:23G0 Z5
18:53:17G30 S-1
Stopped at height -0.757 mm

Results after putting the trigger value up to 70 in stead of the 10 I started with. I followed the guide to setup the 3dtouch (bltouch guide actually) which stated that the trigger value had to be low, since the pulse of the sensor is very short. Seems it however has a negative effect on the output when you go low/very low.

[Scachi]

I am using 25 as the trigger value.

[janko]

@scachi let me test that next

I now tried without the resistor between ground / signal wire (since duet 'bragged' about how idiotproof the board is, i felt lucky

results now:
19:18:03G30 S-1
Stopped at height 0.000 mm
19:17:56G0 Z5
19:17:40G30 S-1
Stopped at height 0.065 mm
19:17:32G0 Z5
19:17:24G30 S-1
Stopped at height -0.039 mm
19:17:19G0 Z5
19:17:11G30 S-1
Stopped at height 0.005 mm
19:17:04G0 Z5
19:17:00G30 S-1
Stopped at height -0.013 mm

This seems to be somewhat normal

[dc42]

What happens if you reduce the probing speed (F parameter in the M558 command)?

The probing move is terminated abruptly when the probe triggers, and if the probing speed is too high then it can overshoot.