Archive for August, 2014

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)


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.




Embedded 12V PSU death

The 12V embedded supply that has been doing very nicely on my Mendel 90 ate itself rather with a very enthusiastic pop and the usual smell of burnt electronics.

Thankfully the fuse inside the supply caused it to fail safely (power shut off to the supply input and nothing else was going to burn up), but it means I needed to quickly find a new power supply.

PSU fuse

Blown fuse

 More knowledgeable people than myself suggested it was probably something else that failed. There was a weird mark on the rectifier (and my thinkpad brick died at the rectifier)

Rectifier with odd mark

Rectifier with odd mark

But I think this was the source of the major failure. One of the output mosfets failed blowing black burn marks out towards the small transformer.

Burnt up mosfet

Burnt up mosfet

I have a couple spare 12V server power supplies lying around, and it turns out they convert easily for custom use. See this thread:

My new supply was a Dell AA23300, which there are pinouts for turning on here:

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