ToolChanger HomeC.G

Discussion in 'Tool heads & ToolChanger' started by Thee Gamefanatic, Aug 14, 2021.

  1. Thee Gamefanatic

    Thee Gamefanatic New Member

    Mar 3, 2019
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    So I have noticed a lot of other people having various problems with homing their C-Axis. I have been converting mine from another build to the toolchanger parts and always thought maybe I had some bad wiring.

    • After a long print randomly does not home again. Sometimes it just won't.
    • When doing a fresh home at startup of printer it will turn all the way to home, but not turn back (seems to skip).
    • Remove the cable from Duet during a home, get no response from Duet that there is a problem. Sometimes it would resolve the issue.

    All solutions seem to be around tuning the stall detection and increasing/decreasing the stepper voltage. I tried all those solutions. Even ran new wires. What I found through an accident was, there was almost never an issue with the tool going to the home position, it was only afterward that it would run into a problem. I could move the C-Axis from the Duet screen with no issues. , it was only moving away (unlock position). Once I tried moving the motor past the unlock position. Next, I tried moving the C-Axis past the unlock step and found I could get the Lock macro to work every time.

    So what I have done now is once the Stepper get's set to the 0 position, I next invoke the Lock macro which moves it past the unlocked position, then invoke the unlock.

    So far, even after a 10 hour print and a week's worth of other prints the fix appears to be holding.

    ; First we give the system a "kick" at full power
    M913 C100 ; Set C motor 100% current
    M400 ; Wait for moves to finish
    G1 H2 C-5 F5000 ; kick it!!

    ; Now home
    G91 ; Relative coordinates
    M913 C85 ; Crash fallback: Set C motor to lower current, but <= 80 was unstable low.
    G1 H1 C10 F5000 ; Space min end or stall at max end, needed for acceleration towards near min end.
    G1 H1 C-1000 F5000 ; Try to stall at min end, reset to min-axis M203 = 0 coordinate

    G92 C0 ; Crash fallback: coordinates reset to 0 in case stall did not reset to min-axis M203 coordinate
    G90 ; Back to absolute coordinates
    M913 C100 ; Set C motor 100% current

    ;Open Coupler
    ; in most cases the homing will find 0, but not move back (for whatever reason)
    ; if we lock the coupler first this moves past the unlock more times than not.
    ; find that unlocking afterwards works... Go figure.
    M98 P"/macros/Tools/Tool-Lock"
    M98 P"/macros/Tools/Tool-Unlock"
  2. KHH

    KHH Member

    Nov 15, 2020
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    I think scan all your script for M906 and M913 commands, you might have a script somewhere tweaking the power via one of these. e.g:
    ; Change 18/11, dropping all except C to 85% of rated
    M906 X1650 Y1650 Z1130 C400 E1420:1420:1420 I30 ; Set motor currents (mA) and motor idle factor in percent
    ; Drop steppers to 75% of max
    ;M913 E75:75:75:75
    ;Stall Detection
    M915 C S5 F0 H200 ; Coupler

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