The Pain of a Dual Extruder Kossel Mini

For my 4th 3d printer I wanted the speed of a delta, and dual extruders for soluble support material or multi color or whatever. (For those keeping track at home the order has been MakerFarm Prusa i3, Mendel 90, Prusa i3 edge, Kossel mini dual-extruder, not discussed yet).

This has been quite a journey. I started on this in [mumble] and am still not quite there yet.

Ok, so getting Kossel mini vitamins and printing the parts is easy. (Misumi takes forever to ship 1515 from overseas but whatever)

Building two e3d v5 1.75mm bowden hotends and wiring them up to RAMPS is easy.

Configuring marlin for a delta and dual extruders is easy.

Redesigning the Kossel mini end effector to hold two e3d hotends was… possible.

Dual e3d v5 in standard size kossel end effector.

Dual e3d v5 in standard size kossel end effector.

And it turns out my dual spool holder idea works pretty well.

But printing with dual extruders on a delta found a bug in Marlin where it would try to move in cartesian space (not delta space) after changing tools, which would attempt to destroy the machine. And sort of did.

[The very simple looking belt holders on the standard carriage shear off rather than letting the belt slip]

I fixed that in Marlin but never quite got the nozzles aligned and everything calibrated right.

Since then I’ve moved from airtripper extruders to RichRap’s greg’s wades variant, and to a 5 axis Smoothie board. I’ve also replaced my open loop belts with closed loop ones as in the standard BOM. (I didn’t find a closed loop variant of the carriages that worked for me)

IMG_4754

Here’s my bulleted list of current problems

  • Solvable: The electronics don’t have an enclosure now so it’s not really a printer that can be moved.
  • Solvable: I haven’t ever finished calibrating the position of the two nozzles because I end up changing how the hotends are mounted before I get that far.
  • Hard: The nozzles are very difficult to align to the same height, so typically one will mess up the printing of the other.
  • Hard: With the extra weight of the two e3d (v5) hotends and fan duct, even an acceleration of 3000 causes very visible ringing at corners. I THOUGHT THIS WAS SUPPOSED TO LET ME GO FASTER!

Sorry I don’t have more good pictures.

-End

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  1. #1 by Jay Sprenkle on January 9, 2015 - 9:48 am

    I’m a newb at printing but looking at a mini kossel. Is dual head needed for printing soluable filamant or can you change filament during a print? Thanks

    • #2 by sphereinabox on January 18, 2015 - 1:50 pm

      You can change filament during a print, but you wouldn’t want to print soluble support that way because you’d need to change filament on every layer.

      Also, I don’t recommend a delta as anyone’s first printer.

      • #3 by jaysprenkle on January 18, 2015 - 6:24 pm

        Looks like the only reasonably priced unit with a decent print volume. I have a specific use in mind and a 4 inch maximum size will not work very well. I have a minor in Electrical Engineering and a lifetime of programming experience. I found a kit with everything included and pretty good reviews. Is it that bad?

      • #4 by sphereinabox on January 22, 2015 - 3:56 pm

        Unless you have a probe on your delta, getting the bed movements aligned takes several annoying hours of iteration.

  2. #5 by sphereinabox on March 13, 2015 - 9:10 am

    Alan (email removed)

    The bug in Marlin was that it tried to move to the previous position on tool change. This is done in cartesian space, not delta space. I commented out the corresponding lines in Marlin_main.cpp (look for the “move to the old position if ‘F’ was in the parameters” comment). I’m not sure if this is fixed on Github yet.

    I’ve since switched to a smoothie board and smoothie firmware.

  3. #6 by Matthew Van Arsdale on March 16, 2015 - 7:19 am

    Have you made any progress? Why didn’t you jump from 2 to 3 hot ends instead?

    • #7 by sphereinabox on November 17, 2015 - 3:14 pm

      I’ve been working on other projects.

      You can’t buy a smoothie board with more than 5 motors right now, which limits to 2 extruders. Besides, who wants to align that many things?

  4. #8 by daniel on May 25, 2016 - 6:31 am

    you can have stl dual kossel mini effector?

    • #9 by sphereinabox on November 18, 2016 - 5:08 pm

      I designed my own but didn’t release it because I wasn’t happy with how it worked. It’s probably not worth releasing now because you can’t even buy the e3d V5 any more. The cyclops or chimera is better for this, and I think there are kossel mini parts for both.

  1. Ormerod and Mini Kossel 3D printer kits compared | David Crocker's Solutions blog

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