trigger height always changes



  • I'm trying to level my bed, but having issues with the trigger height always changing. (duet wifi, bltouch, latest firmware)
    I follow the instruction and set z = 0 in the middle of my bed.
    i perform a trigger height test and say i get consistent results of 1.232
    i go into my config.g and change my G31 to G31 X37 Y0 Z1.23
    when i save, it restarts my duet wifi, i go back and perform the same steps and this time my trigger height in the middle is different.
    i put in the new number 0.9 in the config. save, reboot perform test again, trigger height is once again different.

    I'm using mesh calibration, but struggle to get a good first layer, i always have to baby step up or else it grinds.

    thoughts or suggestions about what may be my problem?
    Thanks!
    (note my bltouch is the newest version and set at the correct height)


  • Moderator

    Please post your config and homing files.

    Are you loading the heightmap automatically at boot?
    Are you clearing any bed transform before measuring?
    What exactly are you sending to measure the trigger height?



  • @Phaedrux said in trigger height always changes:

    you loading the heightmap automatically at boot?
    Are you clearing any bed transform before measuring?
    What exactly are you sending to measure the trigger height?

    sorry it's a little messy. but here are my files.
    I'm using a macro that has 2 lines to measure
    G1 Z10 F1000
    G30 S-1
    just to be sure it wasn't me. i changed my trigger height, saved, config and all i did was restart and it was different, i didn't re-calibrate z0 and it's still different after every reboot
    I'm using M561 to clear the bed before i measure.

    config

    ; General preferences
    G90                                     ; send absolute coordinates...
    M83                                     ; ...but relative extruder moves
    M550 P"FT5-R1 Custom"                   ; set printer name
    
    ; Network
    M552 S1                                 ; enable network
    M586 P0 S1                              ; enable HTTP
    M586 P1 S0                              ; disable FTP
    M586 P2 S0                              ; disable Telnet
    
    ; Drives
    M569 P0 S0                              ; physical drive 0 goes forwards
    M569 P1 S0                              ; physical drive 1 goes forwards
    M569 P2 S0                              ; physical drive 2 goes forwards
    M569 P3 S0                              ; physical drive 3 goes forwards
    M584 X0 Y1 Z2 E3                        ; set drive mapping
    M350 X16 Y16 Z16 E16 I1                 ; configure microstepping without interpolation
    M92 X80.80 Y80.80 Z401.00 E435.00       ; set steps per mm
    M566 X600 Y600 Z50 E600			; set maximum instantaneous speed changes (mm/min)
    M203 X6000.00 Y6000.00 Z1000.00 E6000.00 ; set maximum speeds (mm/min)
    M201 X1000 Y1000 Z300 E2000		; set accelerations (mm/s^2)
    M906 X850 Y900 Z950 E850 I30            ; set motor currents (mA) and motor idle factor in per cent
    M84 S30                                 ; Set idle timeout
    
    ; Axis Limits
    M208 X0 Y0 Z0 S1                        ; set axis minima
    M208 X300 Y300 Z345 S0                  ; set axis maxima
    
    ; Endstops
    M574 X1 S1 P"!xstop"                            ; configure active-high endstop for low end on X via pin xstop
    M574 Y1 S1 P"!ystop"  
    ; M950 H4 C"nil"
    M950 P2 C"^exp.heater4" Q50
    M950 P3 C"^exp.heater5" Q50
    M950 P4 C"^exp.heater6" Q50
    M950 P5 C"^exp.heater7" Q50
    ; Z-Probe
    M574 Z1 S2                              ; set endstops controlled by probe
    ; M307 H3 A-1 C-1 D-1                     ; disable heater on PWM channel for BLTouch
    M950 S0 C"exp.heater3" ; create servo/gpio 0 on heater 3 pin on expansion connector
    M558 P9 C"^zprobe.in" H5 F100 T4000 A5 R0.3 S0.005 B1  ; BLTouch connected to Z probe IN pin
    G31 X37 Y0 Z0.98                   	; set Z probe trigger value, offset and trigger height
    M557 X40:280 Y15:280 P5                ; define mesh grid
    
    ; Heaters
    M308 S0 P"bed_temp" Y"thermistor" T100000 B4138 R4700	; define bed temperature sensor
    M143 H0 S120                            ; set temperature limit for heater 0 to 120C
    M950 H0 C"bed_heat" T0 ; heater 0 uses the bed_heat pin, sensor 0
    M308 S1 P"e0_temp" Y"thermistor" T100000 B4138 R4700	; define bed temperature sensor
    M143 H1 S280                            ; set temperature limit for heater 1 to 280C
    M950 H1 C"e0_heat" T1 ; heater 1 uses the e0_heat pin and sensor 1
    
    ; Fans
    M950 F0 C"fan0" Q500                           ; create fan 0 on pin fan0 and set its frequency
    M106 P1 S0 I0 F500 H-1                  ; set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M950 F1 C"fan1" Q500                           ; create fan 1 on pin fan1 and set its frequency
    M106 P0 S1 I0 F500 H1 T45               ; set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
    
    ; Tools
    M563 P0 D0 H1 F1                        ; define tool 0
    G10 P0 X0 Y0 Z0                         ; set tool 0 axis offsets
    G10 P0 R0 S0                            ; set initial tool 0 active and standby temperatures to 0C
    
    ; Custom settings are not defined
    
    ; STARTUP TUNE
    ;
    G4 S5 ; pause 5 seconds
    M300 P200 S1975.53
    G4 P201
    M300 P200 S2217.46
    G4 P201
    M300 P200 S1975.53
    G4 P201
    M300 P200 S2793.83
    G4 P201
    M300 P200 S2489.02
    G4 P201
    M300 P200 S2217.46
    G4 P201
    M300 P200 S2489.02
    G4 P201
    M300 P200 S2959.96
    G4 P201
    M300 P300 S3520.00
    

    home all

    G91                     ; relative positioning
    ;G1 H2 Z5 F6000          ; lift Z relative to current position
    G1 H1 X-305 Y-305 F1800 ; move quickly to X and Y axis endstops and stop there (first pass)
    G1 H2 X5 Y5 F6000       ; go back a few mm
    G1 H1 X-305 Y-305 F360  ; move slowly to X and Y axis endstops once more (second pass)
    G90                     ; absolute positioning
    G1 X15 Y15 F6000        ; go to first bed probe point and home Z
    G30                     ; home Z by probing the bed
    
    

  • Moderator

    @ianborg said in trigger height always changes:

    G31 X37 Y0 Z0.98

    Your G31 is missing the P value. Add P25. Not sure what the default is, or if this would make a difference, just something I noticed.

    I'd also try reducing your Z max feed rate. Try 500 and see if it makes an improvement.

    Also check your BLTouch mount to ensure that it's stable and fully vertical. Also the base of the probe should be ~2mm above the nozzle tip for best results.



  • @Phaedrux said in trigger height always changes:

    @ianborg said in trigger height always changes:

    G31 X37 Y0 Z0.98

    Your G31 is missing the P value. Add P25. Not sure what the default is, or if this would make a difference, just something I noticed.

    I'd also try reducing your Z max feed rate. Try 500 and see if it makes an improvement.

    Also check your BLTouch mount to ensure that it's stable and fully vertical. Also the base of the probe should be ~2mm above the nozzle tip for best results.

    that may have actually helped 🙂 I rebooted 3 times and got 1.1x trigger heights each time. which is what i would have expected and wasn't seeing. so i'm going to adjust and try it all again.
    1 question, my bltouch is set to be 8.3 mm above. most of my google searching says that's the number. i printed a 8.3mm jig and used that to set the height. is there something specific with the duet that it has to be 2mm??
    appreciate the help!


  • Moderator

    @ianborg Sorry, mental lapse on my part.

    It should be ~8mm above the nozzle tip and that will result in a trigger height of ~2mm.



  • @Phaedrux no worries. okay so sorta the same problem
    I confirmed if i set the z0 and do a trigger height, i get like 1.1, if i do nothing but reboot, i'll get a trigger height 1.1 each time.
    if i go into my config and change the config from 1.0 to 1.1, and reboot, i now get a trigger height of 1.2x
    change the config, put it 1.2 (no rezero of Z) i now get a trigger of 1.3

    so that leads me back to the the problem of the 1st layer, i'm always having to baby step to get a good first layer and i'm wondering if the above problem is why.

    is there a way to add a +0.5 Z (or whatever number) to my config on top of what i have so i don't have to baby step each print?


  • Moderator

    @ianborg said in trigger height always changes:

    B1

    Try removing the B1 from your M558 (which turns off heaters during probing). Perhaps we're dealing with a thermal expansion issue. I assume you're doing the testing with the bed at temp.

    Also, have you PID tuned your bed heater?



  • I'm curious as to what this turns out to be. Sometimes I feel like I'm playing wack-a-mole trying to set the height on my delta with a smart effector. I don't seem to have this problem on my cartesian.


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