Help configuring U axis

  • I'm attempting to convert the extra extruder driver(4) into a "U" axis for positioning a purge bucket. I plan to use motor stall rather than the normal endstops. The motion calibrates into degrees (25) to swing the bucket into position. The effect from Home-All is that U axis homing fails and the motor does not budge (no power to the stepper). So here is a precis of the key config.g changes in the order in which they are written.

    M569 P4 S1 ; Drive 4 goes forwards
    M584 U4 ; XX Create U4 axis on second extruder port
    M92 X160 Y160 Z160 E509.93:17.78 ; XX Set steps per mm (U axis = steps per degree of rotation = 17.78
    M566 X300 Y300 Z300 E500:250 ; XX Set maximum instantaneous speed changes (mm/min) (U axis = 250 deg/min)
    M201 X1836.33 Y1836.33 Z1836.33 E3000:500 ; XX Set accelerations (mm/s^2) - (U axis = 500 deg/s^2)
    M906 U1200 ; XX Set U axis motor current
    M574 U4 S3 ; XX > U axis motor load detect

    Help with this will be appreciated - I'm pretty G-code stupid.

  • @balrags All those motor commands that have colon separated values for E need to be in the format Xnn Ynn Znn Unn Enn. So one extra entry for the U axis and only one entry for the extruder.
    You also need to add P4 to the end of M584 to make the U axis visible.

  • @deckingman That did the trick - thanks so much. I am confused, however, as to the meaning of axis "visibility". To me, in our primitive American version of English, that would indicate that something exists and is real and operable but just not optically available. Somehow I think that is not the meaning here.

  • @balrags I agree . As a person born and raised in England, the terminology of "hiding" axes or making them "visible" in this context is confusing and doesn't fully explain the concept.

    The documentation for the "P" parameter in M584 states (quote):

    "Pnnn Number of visible axes, defaults to the total number of axes configured."

    Perhaps the term "active" instead of visible might be better? But I can see that this would lead to further confusion because tools can be active or idle but are always visible on the web interface.

    Or maybe it just needs a line in the documentation which explains that axes need to be visible before they become operable (or some such). Maybe a moderator will stumble upon this thread and clarify the documentation somehow.

  • How about >>>>>
    I think I leave it there unless you can improve upon it.

  • @deckingman Oops! The new U axis works perfectly but I didn't bother to run a print. Now the extruder doesn't function. May I impose upon you or anyone to review this config file. ( Note I tried the M584 line both P4 and P5 - neither worked )
    CONFIG 06-05.png

  • @balrags Can you post your entire config.g. I don't see a tool defined anywhere and that is likely where the problem lies.

  • @deckingman This is the balance of the config file from endstops to the end.config2.png

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  • @balrags Thanks. It isn't the tool definition that's the problem, it's the motor mapping (I think). When you create new axis, you need to explicitly define everything else (I think). You've also used P5 instead of P4 which might, or might not bugger things up.

    So change this.............
    M584 U4 P5

    To this..................
    M584 X0 Y1 Z2 U4 E3 P4

    Let me know if that fixes it.

  • That did it, thanks so much for taking the time. I played with the P4-P5 value because I thought perhaps the E3 might be considered an axis.
    I'll shout you a pint next time I cross the pond - alas not soon.

  • @balrags Glad that fixed it.

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