Z height offset changing



  • I use mesh bed levelling.
    If I restart my printer. And then warm it up and home it, then start a print, it will have the proper z offset. -0.8mm

    After I run a print. If I home all axies again and run another job, the z offset seems a few mm lower then I should be and the first layer is ruined.

    Not sure why this is happening.
    I have to pull power and restart for each new print.

    Running 1.21rc4
    Corexy



  • Can you post your config.g and homeall.g?



  • Disable mesh bed leveling and then home the printer.



  • config.g

    ; Configuration file for Duet WiFi
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool on Sun Oct 23 2016 10:30:40 GMT-0400 (Eastern Standard Time)

    ; General preferences
    M111 S0 ; Debugging off
    G21 ; Work in millimetres
    G90 ; Send absolute coordinates...
    M83 ; ...but relative extruder moves
    M555 P2 ; Set firmware compatibility to look like marlin
    M557 X20:260 Y0:240 S14 ; define a grid covering the XY area indicated with the specified grid spacing
    M376 H10 ; Taper grid after 10mm

    M667 S1 ; Select CoreXY mode
    M208 X0 Y0 Z0 S1 ; Set axis minima
    M208 X280 Y250 Z300 S0 ; Set axis maxima

    ; Endstops
    M574 X1 S1 ; Reverse X endstop
    M574 Y2 S1 ; Y Max Stop
    ;M574 E0 S1 ; Endstop for Zprobe on E0
    M558 P4 X0 Y0 Z1 H4 F120 T6000 I1 ; Set Z probe type to switch, the axes for which it is used and the probe + travel speeds
    G31 P600 X0 Y0 Z-1.8 ; Set Z probe trigger value, offset and trigger height
    M581 E1 T1 ; Set Filament Sentinel to trigger and Pause print, if filament runs out

    ; Drives
    M569 P0 S0 ; Drive X goes backwards
    M569 P1 S0 ; Drive Y goes backwards
    M569 P2 S0 ; Drive Z goes forwards
    M569 P3 S0 ; Drive E3D Titan goes backwards
    M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
    M92 X200 Y200 Z800 E418.5 ; Set steps per mm
    M566 X800 Y800 Z20 E800 ; Set maximum instantaneous speed changes (mm/min)
    M203 X12000 Y12000 Z1500 E1800 ; Set maximum speeds (mm/min)
    M201 X2000 Y2000 Z250 E250 ; Set accelerations (mm/s^2)
    M906 X1200 Y1200 Z1300 E900 I30 ; Set motor currents (mA) and motor idle factor in per cent
    M84 S30 ; Set idle timeout

    ; Heaters
    M143 S280 ; Set maximum heater temperature to 280C
    M301 H0 S1.00 P10 I0.1 D200 T0.4 W180 B30 ; Use PID on bed heater (may require further tuning)
    M305 P0 T100000 B4138 C0 R4700 L0 H0 ; Set thermistor + ADC parameters for heater 0
    M305 P1 X200

    ; Tools
    M563 P0 D0 H1 ; Define tool 0
    G10 P0 X0 Y0 ; Set tool 0 axis offsets
    G10 P0 R0 S0 ; Set initial tool 0 active and standby temperatures to 0C

    ; Network
    M550 PTitanXY ; Set machine name
    M552 S1 ; Enable network and acquire dynamic address via DHCP

    ; Fans
    M106 P0 S0.3 I0 F500 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P1 S1 I0 F500 H1 T45 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
    M106 P2 S1 I0 F500 H1 T45 ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned on

    ; Custom settings are not configured



  • ; homeall.g
    ; called to home all axes
    ;
    ; generated by RepRapFirmware Configuration Tool on Sun Oct 23 2016 10:30:40 GMT-0400 (Eastern Standard Time)

    ; Relative positioning
    G91

    ; Lift Z
    G1 Z5 F6000 S2
    G90

    ; Move towards X and Y axis endstops (first pass)
    G91
    G1 X-385 F2600 S1
    G1 Y385 F2600 S1
    G90

    ; Go back a few mm
    G91
    G1 X5 F6000
    G1 Y-5 F6000
    G90

    ; Move slowly to axis endstops once more (second pass)
    G91
    G1 X-285 F360 S1
    G1 Y285 F360 S1
    G90

    G91 ; relative mode
    G1 Z4 F200 S2 ; raise head 4mm to ensure it is above the Z probe trigger height
    G90 ; back to absolute mode
    G1 X140 Y140 F2000 ; put head over the centre of the bed, or wherever you want to probe
    G30 ; lower head, stop when probe triggered and set Z to trigger height

    ; Uncomment the following lines to lift Z after probing
    G91
    G1 Z20 F1000
    G90



  • Hi. Your trigger height in G31 command is -1.8 . What kind of probe are you using? If its not piezo, then this should be positive value. And i belive -1.8 is too much even if it is piezo.



  • my Z endstop is special. it uses the nozzle and move the entire gantry vertically until its triggered. trust me that number is correct



  • maybe since its a negative value that is somehow causing the firmware to miscalculate something, since its not typical



  • @adamfilip, did you try out my comment?
    I suppose this is the printer we are talking about?



  • Yes a revised version of that printer. I will try adding a G29 S2 at my ending code, and see if that makes any difference



  • on my first test, adding the G29 S2, seems to have worked


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