BLTouch getting triggered

garyd9

Here's an irony:

I'm going to be returning my BLTouch (to amazon.) When I first installed it, 5 probes in a row at the exact same place would differ by no more than about 0.03mm. That was tolerable. (Not great, but good enough to print with a .4mm nozzle.)

After using it for less than a week, 5 readings in a row at the exact same location differ by nearly 0.2mm. At that range, my nozzle would be crashing into my glass build plate or I'd be air printing.

Tried cleaning it, verified my mounting, verified my wiring, etc. I spent hours on google, but I'm quite certain my Duet board isn't impacted by a bug in Marlin. From what I've read, some people just have issues with the BLTouch… some have luck with a replacement, others don't.

Maybe I'll reconsider the mini IR sensor.... or maybe I'll just slide pieces of paper under my nozzles every couple of days.

pao_wikhan

that is exactly my issue. now my offset is at 6mm. which is super weird.

pao_wikhan

im not sure if getting an authentic BLTouch would make a difference, im new to autolevelling so im not really sure.
i tried the NPN probe but it wont work for me as im used to glass printing.

now im quite lost at it.

bartolomeus

I have an original bltouch which is working fine. Here's my homez for reference:

[[language]]
; homez.g
; called to home the Z axis
;
M561			;reset bed compensation
T0 			;select tool
G91 			;relative coordinates	
M280 P3 S160 I1		;release Z probe alarm
G1 Z5 F2000 		;lower bed
G4 P500 		;wait for the bed to lower
G90 			;absolute positioning
G1 X145 Y145 F3000	;move to center
M401			;deploy the probe
G30 			;calibrate Z-axis
M402			;Retract Probe

And the endstop part of config.g:

[[language]]
; Endstops
M574 X2 Y1 S1                            ; Set active high endstops
M574 Z1 S2                               ; Set endstops controlled by probe
M307 H3 A-1 C-1 D-1 			 ; bltouch
M558 P5 X0 Y0 Z1 H3 F250 T3000		 ; bltouch
G31 X-25 Y20 Z2.8 P25			 ; bltouch offset
M557 X15:265 Y25:275 S80		 ; Define mesh grid

pao_wikhan

okay..so i fixed the mean error. now this is my current, i placed a debug mode on the config.g as it is weird it stops at the same place all the time.
still i am able to home with 3 of 5 the probe not alarming.

[[language]]
confg.g

M667 S1                                                                      ; Select CoreXY mode
M208 X0 Y0 Z0 S1                                                             ; Set axis minima
M208 X300 Y285 Z300 S0                                                       ; Set axis maxima

; Endstops
M574 Z0 S2                                                                   ; Set active low endstops (z end stop disabled)
M574 X1 Y1 S1                                                                ; Set active high endstops
M558 P5 X0 Y0 Z1 H7 F100 T3000              ;debug mode
G31 X25 Y0 Z3.31 P30                            ;debug mode
;M558 P5 X0 Y0 Z1 H10 F100 T4000                                             ; Set Z probe type to unmodulated, the axes for which it is used and the dive height + speeds  BLTOUCH
;G31 P5 X0 Y0 Z5                                                             ; Set Z probe trigger value, offset and trigger height BLTOUCH
M557 X0:300 Y0:285 S50                                                   ; Define mesh grid

[[language]]
bed.g

M561 ; clear any bed transform
; Probe the bed at 4 points
G30 P0 X10 Y0 H0 Z-99999
G30 P1 X10 Y265 H0 Z-99999
G30 P2 X275 Y265 H0 Z-99999
G30 P3 X275 Y0 H0 Z-99999 
G30 P4 X145 Y135 H0 Z-99999 S

[[language]]
; homeall.g
; called to home all axes
;
; generated by RepRapFirmware Configuration Tool on Wed Dec 27 2017 18:31:34 GMT+0800 (PHT)
G91                                                                            ; relative positioning
G1 Z7 F800                                                                     ; lift Z relative to current position
M280 P3 S160 I1                                                                ; Clear any alarm
G1 S1 X-305 Y-305 F1800                                                        ; move quickly to X or Y endstop and stop there (first pass)
G1 S1 X-305                                                                    ; home X axis
G1 S1 Y-305                                                                    ; home Y axis
G1 X5 Y5 F360000                                                               ; go back a few mm
G1 S1 X-305 F360                                                               ; move slowly to X axis endstop once more (second pass)
G1 S1 Y-305                                                                    ; then move slowly to Y axis endstop
G90                                                                            ; absolute positioning
G1 X10 Y0 F360000        ; go to first bed probe point and home Z
G30                     ; home Z by probing the bed

was able to have this deviation after placing the bed, then i tried to relevel the bed then i cannot get to mesh completely as it is stopping at the same point.

[[language]]
RepRapFirmware height map file v2 generated at 2018-01-06 20:56, mean error 0.248, deviation 0.204
xmin,xmax,ymin,ymax,radius,xspacing,yspacing,xnum,ynum
10.00,290.00,0.00,270.00,-1.00,108.80,108.80,3,3
  0.029,  0.200,  0.093
  0.010,  0.435,  0.245
  0.110,  0.541,  0.572

pao_wikhan

when it reached that spot on the bed the probe triggers an alarm..which is super weird.

pao_wikhan

my bed is warped lightly on the middle, is that why i cant do a correct calibration?

pao_wikhan

able to do a 9pt mesh compensation, is there a limit to the compensation?

pao_wikhan

ended up doing a 4pt as the middle of the bed is stopping the probing.

dc42

Try increasing the Z dive height parameter, that's H in the M558 command.

pao_wikhan

i'll try with a flat glass to see if it changes, as it might be detecting a super dent or something.
so far right now i think all is good with the 4pt.

pao_wikhan

i noticed that when i hit print another on DWC it does not do the full cycle from homing to g29 S1, it just starts to print right away.
so what i do is after printing i hit the print button on gcode files to print another one.

pao_wikhan

it seems no matter how much dive i do if the bed itself is very warped/distorted the probe will detect the irregularity.
i added glass to the bed and its all better now. able to do a 9pt-25pt on the bed.

Thanks All!

zen

Hi @pao_wikhan

Did you fix the error with probe triggering at very high position? I seem to be having very similar issue. My probe just triggers without even touching the bed.

pao_wikhan

@zen
yep. im using 1.20 firmware and i used p8 on the m558.

zen

It didn't help in my case. This entire thing is driving me crazy, it behaves randomly

dc42

@zen said in BLTouch getting triggered:

It didn't help in my case. This entire thing is driving me crazy, it behaves randomly

To use bltouch we recommend firmware 1.21 (or 2.0beta) and P9 in M558.

zen

@dc42 Yeah, exactly what I'm using. Essentially I tried everything I could.

Is it even possible that Duet is not providing enough amps on 5v rail? BLtouch is like 300mA, so I guess we should be ok here.

Phaedrux

I had a similar situation where the BLTouch would often trigger early. The reason turned out to be that the pin inside the housing was dirty from the factory. There was some sticky residue that would keep it from dropping. The solution in my case was to remove the small set screw at the top of the housing to remove the pin. I then used fine grit sand paper and 99% alcohol and water to clean the pin and the opening of the housing. After reassembly it functioned perfectly.

Even if it's not dirty, you may need to adjust the set screw to adjust the sensitivity, since it's the set screw that acts as the magnetic core to draw up the pin. A half turn one way or the other may be enough to get it tuned properly.

zen

@phaedrux I just disassembled it today, but since I haven't seen any dirt, I didn't clear it. Also I read that grub screw should be exactly 0.3mm from flange. I will set it like this tomorrow and check results.