CNC Tweaking for homing

  • Trying to configure my DuetWifi for CNC use.
    Using expansion header and external DQ542MA stepper drivers.
    using motors 5,6,7

    Currently my cnc machine does NOT have endstops

    I need to be able to move to a Starting position manually and set it as 0,0,0 start point using macro in Web control.

    i need to be able to do Negative Moves in all Axis to get into the right postion
    then apply a G92 X0 Y0 Z0 to Zero everything out as a starting point.

    how do I enable negative moves without homing?

    Here is my config.g script im using which was based on @Catalin_RO file.

    ; General preferences
    M111 S0 ; Debugging off
    M453 ; CNC mode
    G21 ; Work in millimetres
    G90 ; Send absolute coordinates...
    M83 ; ...but relative extruder moves
    M555 P2 ; Set firmware compatibility to look like Marlin
    ; Automatic saving after power loss is not enabled

    ; Endstops

    ; Drives & Axis
    ; Define axis X on drive 5, axis Y on drives 1 and 3, axis Z on drive 2 and dummy axis U on drive 9
    ; Show only axis X, Y and Z
    M584 X5 Y6 Z7 U9 E1:2:3 P3
    ; Set stepper drives parameters for all the used ones
    M569 P5 S1 T2.5:2.5:5:0 ; Drive 5 goes forwards (E2 on Expansion Header)
    M569 P6 S1 T2.5:2.5:5:0 ; Drive 6 goes forwards (E3 on Expansion Header)
    M569 P7 S1 T2.5:2.5:5:0 ; Drive 7 goes forwards (E4 on Expansion Header)

    M350 X16 Y16 Z16 U16 ; Configure microstepping with interpolation
    M906 X2000 Y2000 Z2000 U2000 I30 ; Set motor currents (mA) and motor idle factor in per cent
    M84 S30 ; Set idle timeout
    ; Set axis dynamic parameters
    M92 X400 Y400 Z400 U400 ; Set steps per mm
    M566 X900 Y900 Z12 U900 ; Set maximum instantaneous speed changes (mm/min)
    M203 X2500 Y2500 Z2500 U2500 ; Set maximum speeds (mm/min)
    M201 X150 Y150 Z150 U150 ; Set accelerations (mm/s^2)
    ; Set axis travel distances
    M208 X0 Y0 Z0 U0 S1 ; Set axis minima
    M208 X300 Y300 Z200 U515 S0 ; Set axis maxima
    ; Set axis endstops

    ; Heaters
    M140 H-1 ; Disable heated bed

    ; Tools

    ; Fans

    ; Custom settings are not configured

    ; Miscellaneous
    M501 ; Load saved parameters from non-volatile memory

    ; Change to workplace coordinates set 1

    G92 X0 Y0 Z0

  • administrators

    1. Use M564 H0 to allow movement before homing.

    2. After you have "homed" the printer by sending G92 X0 Y0 Z0, the positive axis limits are set by the values in the M208 S0 command, and the negative axis limits are set by the M208 S1 command. So set up your M208 commands to give the limits you want.

  • Thank you for that suggestion.

    I have another, when using External stepper drivers
    via the expansion board

    is M906 relevant anymore?
    M906 X2000 Y2000 Z2000 U2000 I30 ; Set motor currents (mA) and motor idle factor in per cent

    Should i set this to a low value?

  • administrators

    M906 is not relevant if you are using external stepper drivers only. Likewise M350, M913 and M915 except that if you use M350 after M92, the M350 command will adjust the steps/mm based on the new microstepping.

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