SZP error "Probe already triggered at start of probing move"

[Mr Yod]

I completely removed the BLTouch since it started to not trigger during Z home (and, due to wrong measurements, have my hotend collide with the bed :x ) and I put a SexBolt Z endstop at a fixed position in my HevORT, so I decided to have the auto leveling done via the SZP Scanning Probe on a Duet 3 6HC.

I set it and calibrated with M558.2 and saved the parameters in config.g, the problem is that after doing the calibration with M558.1 and after the auto leveling I get the error "M280: Probe already triggered at start of probing move" and it exits the loop witout, apparently, correcting the 3 Z motors.

What am I missing?

Initial settings and calibration in config.g:

M558 K0 P5 C"0.io6.in" H5 F500:120 T9000 A3 S0.015                ; set Z endstop SexBolt
G31 K0 P500 Z0.55
M558 K1 P11 C"120.i2c.ldc1612" F36000 T36000                      ; sensore induttivo (va usato come secondo sensore perchè la temperatura fa cambiare la misurazione)
G31 K1 Z2 Y-17                                                    ; define probe 1 offsets and trigger height
M558.2 K1 S16 R135826                                             ; set drive current and reading offset

homez.g (usually it gets called without parameters, so it's just T0, G90, G1 and G30 commands)

T0 P0
var x = 144.5
var y = -60
 
if !exists(param.L) || param.L == 1		; per abbassare o meno il piatto (se è chiamata da files che l'hanno già abbassato non lo abbassa ulteriormente)
	G91									; relative positioning
	G1 H2 Z{global.movZ} F9000			; lift Z relative to current position
 
if exists(param.X)						; per fare home Z a coordinate personalizzate
	set var.x = param.X
if exists(param.Y)						; per fare home Z a coordinate personalizzate
	set var.y = param.Y
 
G90										; absolute positioning
G1 X{var.x} Y{var.y} F9000				; move to (var.x, var.y), standard: center of bed
G30										; home Z by probing the bed

mesh.g

var tool = state.currentTool                        ; salva il tool attivo prima di passare al sensore induttivo
T-1 P0
 
G29 S2                                              ; Disable mesh bed compensation
G1 X150 Y70 F30000                                  ; centro del piatto
G1 Z6                                               ; to avoid backlash move to point higher than start of calibration
M558.1 K1 S1.7                                      ; Calibrate probe
G1 X150 Y70 F18000                                  ; near Z stop
G1 Z6
 
T{var.tool} P0                                      ; riattiva il tool attivo

bed.g

G29																; probe the bed and enable compensation
 
var tool = state.currentTool									; salva il tool attivo prima di passare al sensore induttivo
T-1 P0
 
M671 X-8.86:167.349:343.558 Y-10.411:317.799:-10.411 S50
M291 R"Leveling bed" P"Please wait..." T5
 
; --- level bed leveling ---
while true
	; run leveling pass
	; --- probe near lead screws
	G30 K1 P0 X30 Y70 Z-99999									; probe near lead screw #1 - Tiene conto dell'offset della sonda: così va ad X0
	G30 K1 P1 X270 Y70 Z-99999									; probe near lead screw #2
	G30 K1 P2 X150 Y300 Z-99999 S3								; probe near lead screw #3 originale: 220
 
	; check results - exit loop if results are good
	if move.calibration.initial.deviation < 0.02
		break
 
	; check pass limit - abort if pass limit reached
	if iterations = 5
		M291 P"Bed Leveling Aborted" R"Pass Limit Reached"
		abort "Bed Leveling Aborted - Pass Limit Reached"
 
; --- finish up ---
; --- set Z=0 datum which can be affected by leveling ---
T{var.tool} P0													; riattiva il tool attivo
M98 P"homez.g" L1												; home Z
M291 R"Leveling bed" P"Done" T5

[gloomyandy]

@Mr-Yod How are you homing Z on your printer? I don't see any M558.1 in your files, are you running it manually?

[Mr Yod]

@gloomyandy said in SZP error "Probe already triggered at start of probing move":

@Mr-Yod How are you homing Z on your printer? I don't see any M558.1 in your files, are you running it manually?

For homing Z: "I put a SexBolt Z endstop at a fixed position in my HevORT" (I didn't post the basic M558 K0 command for a simple switch, now I updated my first post with it).

As for the M558.1 not present: what do you mean? It's right there, in mesh.g (that gets called with a G29 command).

[gloomyandy]

@Mr-Yod I missed the M558.1 in your mesh.g file.

When you calibrated your szp did you check that the probe is not triggered when some distance from the bed? See:
https://docs.duet3d.com/User_manual/Tuning/scanning_z_probe_calibration#drive-level-and-reading-offset

Also check that the Z probe reading is sensible when the sensor is a long way above the bed. The aim is to get sensible readings (i.e. not 999999) from the minimum height to "infinite" height.

So basically lower the SZP until it shows triggered in DWC then raise it above the bed and check that it never shows a triggered state (or a 9999999 reading) at any height above the trigger height). I'd also check that the height at which it triggers matches what you have configured in your G31 settings.

You might also want to set a dive height (H parameter) for your SZP. Given that the bed may be tilted you may want to make this relatively large to ensure that the probe is well above the possibly tilted bed when the probe operation starts.

[Mr Yod]

@gloomyandy said in SZP error "Probe already triggered at start of probing move":

@Mr-Yod I missed the M558.1 in your mesh.g file.

When you calibrated your szp did you check that the probe is not triggered when some distance from the bed? See:
https://docs.duet3d.com/User_manual/Tuning/scanning_z_probe_calibration#drive-level-and-reading-offset

Also check that the Z probe reading is sensible when the sensor is a long way above the bed. The aim is to get sensible readings (i.e. not 999999) from the minimum height to "infinite" height.

So basically lower the SZP until it shows triggered in DWC then raise it above the bed and check that it never shows a triggered state (or a 9999999 reading) at any height above the trigger height). I'd also check that the height at which it triggers matches what you have configured in your G31 settings.

By "not triggered" what do you mean?
5mm above Z I have a number between 6174 and 6177 (more around 6175) after G29

While the SexBolt is at constant 0 (1000 only when pressed)

DWC 3.5.2

G29
Scanning probe coefficients [-9.680e-3, -1.075e-3, 2.671e-7, -4.845e-11], reading at trigger height 7827, rms error 0.012mm

Maybe that' what I'm failing to understand: what does triggered mean on an analogic probe? The color that highlights the number?
Then at Z3 it's 7034 and white, at Z2.95 it's 7062 and yellow and it stays yellow until Z2 (7810) and becomes red at Z1.95 (7853, at Z0 it's 10790)

At Z30 I get a lot of 999999 (red) and some sporadic ~5220 (white), but generally above Z5.5 I have sporadic 999999 red.

You might also want to set a dive height (H parameter) for your SZP. Given that the bed may be tilted you may want to make this relatively large to ensure that the probe is well above the possibly tilted bed when the probe operation starts.

That I'll try maybe later, when I'll manage to have it working.

[gloomyandy]

@Mr-Yod The trigger value is set with the P parameter to G31, use G31 K1 to find out what it is set to. Any probe value above that setting is considered as the probe being triggered. This value is normally set as part of the M558.1 calibration routine (and is reported as "reading at trigger height xxxxxx"), if you are not running this calibration before you run your G32 bed.g routine you may need to set it to a previously obtained value using G32 P.

If you are seeing readings of 999999 then this means that the probe calibration values from M558.2 are probably invalid. You may want to try running the auto calibration again perhaps with a higher trigger height set in G31. I use 3mm rather than the 2mm you have set. I've found that sometimes the values produced by the auto calibration system simply do not work and then adjusting the drive value (set with M558.2 S) manually up and down provides better results.

I know that @droftarts spent some time working on this so he may be able to provide more help.

[Mr Yod]

@gloomyandy
Ok, now (after calibrating it at Z3) it doesn't give the error.

But now it does all 5 loops because it doesn't manage to be consistent.
EDIT: going slower doesn't have problems.
I'll also try to move the coil further away from the extruder.

Then I'll have to understand how to make the scanning without lifting and lowering the bed on every point (just removing the Z-999999 from G30 makes it ignore said command).