Delta Tool Support Axis

  • administrators

    sga wrote

    Just an idea,

    I was thinking of making an "Air Struder" for a large build kossel. But although it's a proven solution the weight of the extruders are still mostly on the carriages.
    An alternative is balancing with springs but it is not my favorit solution either.
    It might not be much weigh for 2-4 extruders but if you consider a reservoir for paste extrusion it can be 1 kilograms or 2.
    Why not suspend the effectors/paste reservoir to an extra stepper motor with a pulley and have them raise as a function of the current printed layer. So the vertical distance between effector and the airstrudder would stay constant. Basically a height controlled hanging platform about 40 cm above the effector.

    sga promoted me about this request so I though I would split it out from the firmware priorities thread for further discussion. The idea is to use and additional stepper motor or motors to move a multi kg reservoir for paste extrusion on Z so that a reasonably constant distance was maintained between the reservoir and effector.

    The complication comes in in two ways, first its adding an effectively Cartesian axis to a delta printer so both geometries would have to be active. Second as the effector moves in XY the Z distance would have to change in order to maintain the same distance between the reservoir and the pipe.

    Couple of questions:

    Sga, can we remove the second complication with you using a long enough pipe that we only need to worry about moving in Z?

    David, what do you think about generalising this problem to that we can use a gcode/macro to carry out an action on each layer change in the same way we have tool change macros. The layer change macro could jog an secondary axis by a certain amount in this case, or carry out another action in another case.

  • administrators

    It would be easier not to remove the second "complication" and keep the diagonal distance between the effector and the hanging extruder constant. Then the extruder motion would behave exactly like another carriage. Now that we have support for additional axes, this would be fairly simple to implement.

    In practice, keeping the diagonal distance constant probably isn't ideal. When the effector is not below the extruder, the Bowden tube will bend into an S shape so the extruder should be a bit lower than the diagonal distance would imply. I think we can allow for that by configuring the "rod length" of the extra axis to be a little shorter than the Bowden tube length and then adding a Z offset.

    There remains the problem of what to do during homing when the carriage positions are not known.

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