Nozzle tip is not at correct height before start of print



  • Hi
    I had posted previously about the fact that when I begin a print, I have some start g code that homes all axis, primes some filament and then begins to print. the problem is that when the print starts the nozzle is about 5mm above the heatbed, so I stop the job, reload the code file again, and start the print everything is fine and nozzle is at correct height. I have posted my config file and home z and home all files also. What is wrong ?

    ; Configuration file for Duet WiFi (firmware version 2.03)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool v2.1.3 on Wed Nov 27 2019 02:27:21 GMT-0500 (EST)

    ; General preferences
    G90 ; send absolute coordinates...
    M83 ; ...but relative extruder moves
    M550 P"ALPHA 300" ; 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 backwards
    M569 P1 S0 ; physical drive 1 goes backwards
    M569 P2 S0 ; physical drive 2 goes backwards
    M569 P3 S0 ; physical drive 3 goes backwards
    M584 X0 Y1 Z2 E3 ; set drive mapping
    M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
    M92 X80.00 Y80.00 Z1600.00 E311.00 ; set steps per mm
    M566 X900.00 Y900.00 Z12.00 E120.00 ; set maximum instantaneous speed changes (mm/min)
    M203 X6000.00 Y6000.00 Z300.00 E4200.00 ; set maximum speeds (mm/min)
    M201 X500.00 Y500.00 Z20.00 E250.00 ; set accelerations (mm/s^2)
    M906 X1050 Y1050 Z1250 E1050 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 Z190.19 S0 ; set axis maxima

    ; Endstops
    M574 X1 Y1 Z2 S0 ; set active low end endstops

    ; Z-Probe
    ;M558 P0 H5 F120 T6000 ; disable Z probe but set dive height, probe speed and travel speed
    ;M557 X15:215 Y15:195 S20 ; define mesh grid

    ; Heaters
    M305 P0 T100000 B4138 R4700 ; set thermistor + ADC parameters for heater 0
    M143 H0 S80 ; set temperature limit for heater 0 to 80C
    M305 P1 T100000 B4138 R4700 ; set thermistor + ADC parameters for heater 1
    M143 H1 S260 ; set temperature limit for heater 1 to 260C

    ; Fans
    M106 P0 S1 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 H-1 ; set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned OFF

    ; Tools
    M563 P0 S"NOZZLE " D0 H1 F0 ; 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

    ; homeall.g
    ; called to home all axes
    ;
    ; generated by RepRapFirmware Configuration Tool v2.1.3 on Wed Nov 27 2019 02:27:21 GMT-0500 (EST)
    G91 ; relative positioning
    G1 H2 Z5 F300 ; 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)
    G1 H1 Z195.19 F300 ; move Z up stopping at the endstop
    G90 ; absolute positioning
    G92 Z190.19 ; set Z to axis minimum (you may want to adjust this)

    ; Uncomment the following lines to lift Z after probing
    ;G91 ; relative positioning
    ;G1 S2 Z5 F100 ; lift Z relative to current position
    ;G90 ; absolute positioning

    ; homez.g
    ; called to home the Z axis
    ;
    ; generated by RepRapFirmware Configuration Tool v2.1.3 on Wed Nov 27 2019 02:27:21 GMT-0500 (EST)
    G91 ; relative positioning
    G1 H2 Z5 F300 ; lift Z relative to current position
    G1 H1 Z195.19 F300 ; move Z up until the endstop is triggered
    G92 Z190.19 ; set Z position to axis minimum (you may want to adjust this)

    ; Uncomment the following lines to lift Z after probing
    ;G91 ; relative positioning
    ;G1 H2 Z5 F100 ; lift Z relative to current position
    ;G90 ; absolute positioning



  • @ScaraMan said in Nozzle tip is not at correct height before start of print:

    .............. I have some start g code that homes all axis, primes some filament and then begins to print. the problem is that when the print starts the nozzle is about 5mm above the heatbed, so I stop the job, reload the code file again, and start the print everything is fine and nozzle is at correct height.

    From that, I'd say that the source of the problem lies within that start.g code. Can you post that too.



  • ;FLAVOR:RepRap
    ;TIME:32505
    ;Filament used: 11.5317m
    ;Layer height: 0.25
    ;Generated with Cura_SteamEngine 3.6.0
    T0
    M190 S60
    M104 S210
    M109 S210
    M82 ;absolute extrusion mode
    G1 X30 Y30 Z170
    G92 E0 ; Reset extruder
    G1 X30 Y30 F4000 ;move X/Y to front of printer
    G1 Z15.0 F9000 ;move the platform to 15mm
    G4 5000
    G92 E0 ;zero the extruded length
    G1 F200 E50 ;extrude 10 mm of feed stock
    64 10000
    G92 E0 ;zero the extruded length again
    G4 1000
    M83 ;relative extrusion mode
    G1 F1500 E-6.5
    ;LAYER_COUNT:181
    ;LAYER:0
    M107
    G0 F7500 X173.774 Y25.353 Z0.15
    ;TYPE:SKIRT
    G1 F1500 E6.5
    G1 F1050 X173.893 Y24.815 E0.00518
    G1 X174.089 Y24.3 E0.00518
    G1 X174.357 Y23.819 E0.00518
    continued



  • @ScaraMan I don't see anything amiss with that but at the same time, I don't see anything that calls the homing macros which you referred to when you said "I have some start g code that homes all axis......."

    I did notice that your home Z has a G91 to set the positioning to relative but no G90 to put it back to absolute and there is no G90 in your start gcode that I can see. So if you ran home Z then that start code, the G1 Z15 would move the head by 15mm from it's current position, rather than to 15mm from the bed. That might explain the 5mm difference. If so putting G90 in your start code might fix it, but I don't think I have the full picture of exactly what commands you are sending.



  • @ScaraMan said in Nozzle tip is not at correct height before start of print:

    What exactly are you doing when you start a print? Running homeall.g, then running print gcode, cancelling, running homez.g, then running the print gcode again?

    Your homez.g does not return to absolute positioning. It should be:

    ; homez.g
    ; called to home the Z axis
    ;
    ; generated by RepRapFirmware Configuration Tool v2.1.3 on Wed Nov 27 2019 02:27:21 GMT-0500 (EST)
    G91 ; relative positioning
    G1 H2 Z5 F300 ; lift Z relative to current position
    G1 H1 Z195.19 F300 ; move Z up until the endstop is triggered
    G90 ; absolute positioning
    G92 Z190.19 ; set Z position to axis minimum (you may want to adjust this)

    Without this, any move in the gcode after this would move in relative mode, until it was turned back to absolute mode.

    I don't think you need the G92 Z190.19 at the end of homeall.g and homez.g, as the preceding move is an H1 move, which sets the axis position defined by M208 in config.g (M208 X300 Y300 Z190.19 S0 ; set axis maxima) when it hits the endstop. But not sure why this would effect the first run of the homeall.g

    Also, in the start of your gcode print file:

    ...
    G1 F200 E50 ;extrude 10 mm of feed stock
    64 10000
    G92 E0 ;zero the extruded length again
    ...

    I think that should be G4 10000. Not sure of the effect of this.

    Ian

    Edit: @deckingman spotted the same thing!


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