Snapping Z end stops.



  • Recently finished installing the duet and testing all the things in my wanhao i3 plus. Homing works great heaters work great and everythings reading correctly - however whenever i start my first print the Z axis comes down too far and snaps off the Z endstop. I have confirmed the Z stop is working correctly and it does home correctly but starting a print just snaps the stop off time and time again. Anybody have any ideas what could be causing this?


  • administrators

    Are you saying that it isn't stopping at the Z endstop; or it is stopping but going a little too far before it stops? Or it stops at the right place, but subsequently the print head moves too low?

    Please post your homeall.g, homez.g and config.g files, and tell us what type of Z endstop or probe you are using for Z homing.



  • The whole gantry comes down too far and subsequently nozzle and everything else pushes the bed down on its springs. Its a regular microswitch end stop no Z probe as yet.

    ; Configuration file for Duet WiFi (firmware version 1.20 or newer)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool on Thu Mar 15 2018 17:14:58 GMT+0000 (GMT)

    ; General preferences
    G90 ; Send absolute coordinates…
    M83 ; ...but relative extruder moves

    ; Network
    M550 PWendell ; Set machine name
    M551 P ; Set password
    M552 S1 ; Enable network
    M587 S"" P"" ; Configure access point. You can delete this line once connected
    M586 P0 S1 ; Enable HTTP
    M586 P1 S0 ; Disable FTP
    M586 P2 S0 ; Disable Telnet

    ; Drives
    M569 P0 S1 ; Drive 0 goes forwards
    M569 P1 S1 ; Drive 1 goes forwards
    M569 P2 S0 ; Drive 2 goes backwards
    M569 P3 S1 ; Drive 3 goes forwards
    M350 X128 Y128 Z128 E16 I0 ; Configure microstepping without interpolation
    M92 X640 Y640 Z3200 E200 ; Set steps per mm
    M566 X900 Y900 Z12 E120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X12000 Y12000 Z1200 E3000 ; Set maximum speeds (mm/min)
    M201 X1000 Y1000 Z100 E5000 ; Set accelerations (mm/s^2)
    M906 X855 Y855 Z855 E855 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 X200 Y200 Z180 S0 ; Set axis maxima

    ; Endstops
    M574 X1 Y1 Z1 S0 ; Set active low endstops
    M558 P0 H5 F120 T6000 ; Set Z probe type to switch and the dive height + speeds
    G31 P500 X0 Y0 Z2.5 ; Set Z probe trigger value, offset and trigger height
    M557 X25:175 Y25:175 S20 ; Define mesh grid

    ; Heaters
    M305 P0 T100000 B3988 C0 R4700 ; Set thermistor + ADC parameters for heater 0
    M143 H0 S120 ; Set temperature limit for heater 0 to 120C
    M305 P1 T100000 B4725 C7.060000e-8 R4700 ; Set thermistor + ADC parameters for heater 1
    M143 H1 S280 ; Set temperature limit for heater 1 to 280C

    ; 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 H T45 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
    M106 P2 S1 I0 F500 H T45 ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned on

    ; Tools
    M563 P0 D0 H1 ; 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

    ; Automatic power saving
    M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" ; Set voltage thresholds and actions to run on power loss

    ; Custom settings are not configured

    ; Miscellaneous
    T0 ; Select first tool



  • ; homeall.g
    ; called to home all axes
    ;
    ; generated by RepRapFirmware Configuration Tool on Thu Mar 15 2018 17:14:58 GMT+0000 (GMT)
    G91 ; relative positioning
    G1 Z5 F6000 ; lift Z relative to current position
    G1 S1 X-205 Y-205 F1800 ; move quickly to X and Y axis endstops and stop there (first pass)
    G1 X5 Y5 F6000 ; go back a few mm
    G1 S1 X-205 Y-205 F360 ; move slowly to X and Y axis endstops once more (second pass)
    G1 S1 Z-185 F1800 S1 ; move Z down stopping at the endstop
    G90 ; absolute positioning
    G92 Z2.5 ; set new Z position
    ;G1 Z5 F100 ; uncomment this line to lift the nozzle after homing



  • ; homez.g
    ; called to home the Z axis
    ;
    ; generated by RepRapFirmware Configuration Tool on Thu Mar 15 2018 17:14:58 GMT+0000 (GMT)
    G91 ; relative positioning
    G1 Z5 F6000 ; lift Z relative to current position
    G1 S1 Z-185 F1800 ; move Z down until the switch triggers
    G92 Z0 ; set Z position to trigger height

    ; Uncomment the following lines to lift Z after probing
    ;G91 ; relative positioning
    ;G1 Z5 F100 ; lift Z relative to current position
    ;G90 ; absolute positioning



  • G31 P500 X0 Y0 Z2.5
    I bet this is the problem. Z should be 0 i think



  • @Threevee:

    G31 P500 X0 Y0 Z2.5
    I bet this is the problem. Z should be 0 i think

    Nah that didn't do it.


  • administrators

    You have this in homeall.g:

    G1 S1 Z-185 F1800 S1 ; move Z down stopping at the endstop
    G90 ; absolute positioning
    G92 Z2.5 ; set new Z position

    but this in homez.g:

    G1 S1 Z-185 F1800 ; move Z down until the switch triggers
    G92 Z0 ; set Z position to trigger height

    The first tells the firmware (in the G92 command) that your Z homing switch triggers at Z=2.5mm. The second says your Z homing switch triggers at Z=0mm. So at least one of them is wrong. What height does your Z homing switch actually trigger at?



  • Zero. Thanks for that ill give it a go tonight!


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