Parking Magnetic Dual Extruder Setup Advice

  • I'm planning on retrofitting my current Prusa i3 style printer with a magnetic dual parking extruder system like these:

    Parking dual extruder, Prusa i3 X axis mod, hexagon extruders

    Dual parking carriage extruder Prusa i3 | E3D & 1730 FMH

    Parking magnetic dual extruder E3D V6 by HalenTech

    plus changing from smooth rods to linear rails on all axis, enclosing the printer, etc.

    However, I'm a confused on how I might go about implementing this with the Duet. Since this isn't an IDEX, there isn't really a set guide for how to accomplish this (not going with IDEX since implementing that would require me to get at a DueX2 expansion board; using this method I only need the 5 drivers on the Duet itself). If I were to place a X_MAX and X_MIN endstop where each tool is parked, that would probably affect homing, unless I always leave the carriage with the electromagnets coupled with a tool at the beginning/end of a print. I wish to avoid this, as it seems like a clunky work around.

    I was digging around the forum and saw that @Scachi has a machine with the same system I'm trying to implement, and from the pictures posted it seems like there is only one x-axis endstop with a rod on the tool pickup carriage extending above the tool on the right (assuming that is to home the x axis).

    I would assume that when doing homing with a system like that, the y-axis would home normally, with the x-axis homing being done with the tool pickup carriage, and since it doesn't need the tool attached it can freely go to the center of the build plate and home the z-axis and perform a mesh grid leveling sequence.

    Just looking for confirmation that my logic is sound or advice on how to implement this further/better/smarter, appreciative for any and all help that anyone can provide.

  • Hi,

    you are right, I did use the x-axis max endstop that got triggered by the pickup carriage, no changes to the endstops required.
    My pickup carriage had first a bltouch, later on a piezo probe attached. This way I could do the Z-probing/mesh grid with the pickup carriages only. This probes position was my x0,y0,z0. I meassured the tools offsets from this position.
    It was neccessary to park both tools before probing. The tools nozzles would have hit the bed before the piezo probe could reach it.

    The parking system worked fine. It was a modifed version of your first link. I was using two e3d v6 hotends via bowden. I was using a geared direct like extruder setup for some time too:
    This printer is no longer active as I have used some parts from it to build a different printer.

  • @Scachi Good to hear nothing special was needed. If you still have them, would you mind sharing your config.g and tool change macros? I think someone else recently posted about trying to set up a systrm like this and it might help them as well.

    Did your setup also include permanent magnets at the parking position? And did you ever encounter any issues with the electromagnet interfering with the stepper motor?

    As far as the tool change went, was it a matter of "middle carriage goes to the x_max endstop to pickup/drop off tool0" and "middle carriage goes to X_min position to pickup/dropoff tool1"?

    Thanks for answering some of my questions, I really appreciate the help.

  • @red-sand-robot
    No, sorry. I don't have any config or cad files from this setup anymore.

    I had a single permanent magnet at each outer side of the hotends carriage.
    They did hold the carriages in their parking position. I used a simple M3 screw put through a soft spring for them to rest on.
    To pickup or release the hotends I moved the pickup carriage +1mm to the sides to make sure it gets a reliable contact. The spring did allow a +4mm movement.

    I had no issues with the electromagnets causing problems. They are far away from the stepper motors. Take a look at the picture
    It is like 6cm away to the x-stepper in its closest position to it when I was using bowden extruders. With the direct extruders I had no problems too.
    I used the electromagnet from the seeed grove modules:
    The nice thing about those is that they work with 5v but they are not very strong so you might want to use other ones or higher voltage. I used a small external 5V power supply and relais to drive/control the magnets.
    For the grove ones I had to make sure the contact plate on the hotend carriage was thick enough and positioned perfectly to get enough holding power.

    Pickup was like you said: move to X, enable magnet, wait for hotend to heatup, continue printing
    For homing Z I move the pickup carriage to both sides first to make sure the hotend carriages are out of their way for z probing to not crash into the bed as their nozzles were at a lower position than my probe.

  • @Scachi Thanks a bunch for the information! Hopefully I'll have a working machine using that system in a few months.

  • @Scachi after picking up the tool, are your electromagnets continuously powered to keep holding the tool or do you have some sort of mechanism to hold it without the electromagnet being powered?

  • @tekstyle they are continuously powered

  • @Scachi

    thank you. you have solved one of the biggest mystery for me. i am trying to design an electromagnet tool change system for a corexy and one problem i have is if for whatever reason i lose power, the extruder will just fall on the build plate since it isn't mounted on rods like on a cartesian with a moving Y.

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