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i3 Magnetic dual hotend mount

by karlzhao314, published

i3 Magnetic dual hotend mount by karlzhao314 Apr 24, 2016
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This is a design for a dual extruder with a simple magnetic coupling, inspired by OpenCircuitDesign's Makergear M2 twin extruder. Essentially, there are 3 parts to it: a middle block to which the belt is affixed and a left and right block that carry the hotends (E3D v6s). The middle block is spaced so that it cannot attach to both the left and right blocks at once, so through some G-code manipulation it's able to detach and reattach to either block without any extra electronics. This allows for each hotend to be manipulated and compensated for separately similar to dual X carriages, which might be able to eliminate ooze and hotend leveling issues.

Visit this link for OpenCircuitDesign's original article and an explanation of the principles behind it:

Project is a work in progress: it's still missing the two parking points on either side of the X rods and no prototype has yet been printed because I'm still awaiting magnets.

Print Settings

Printer Brand:



Prusa i3


Doesn't Matter








Autodesk products export STLs in a strange orientation. Rotate and print as you see fit.



6x 8x10x8mm bronze bushing (LM8UU bearings were too long)
28x 4x2mm round neodymium magnets
M3 bolts and nuts

Assembly: Coming after I make my own prototype

How I Designed This

Inspired by OpenCircuitDesign's magnetic twin extruders for the Makergear M2, designed in Autodesk Fusion 360. Will release design files when the project is complete.

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Awesome design. Such a simple concept. I read through the website you linked and I'm very surprised more printers don't do this.
I was thinking about it, and I think you may be able to simplify the design a bit actually.

  1. You don't really need magnets on the ends for the parking position, because it doesnt matter too much that it is held rigid. The unused carriage can just sit there.
  2. The hotend holding carriages don't need linear bushings/bearings, because that will be handled by the moving carriage. You just need to design in some features that register the position when the carriages attach.

any news ? how did it work ?

got your magnets already?

Not yet, unfortunately. They ship from China, so it could be a couple more weeks. :(

they sure take their time huh?

I'm really curious about this. Would need to rework this for my core-xy though. Test it asap please

I'll try. Still awaiting magnets and time to design parking points.

This is for Prusa i3s only, but you're welcome to design a version for yourself :)

luckily I made my x-axis i3 compatible so it should be easy.