Dual material/color printer

Ultimaker 2+ printer is a great tool to own. The printer still always works.

But it lacks a second color (/material) option. The 1st generation UM2+ printers were already prepared, supporting a second extrusion train: heater & feeder. Also the Marlin code is prepared for this. So adding steppers & heaters is quite straight forwards.

Also the print head allows for a 2nd bowden tube, so basically it’s quite easy to install a second heater+nozzle system.

Ofcourse I also tried that, aligning both nozzels at the same height & start prining. Like many others, I also came to the same conclusion: this does not work.

Why?

Picture courtesy: researchgate.net

Altough I don’t know the exact physical behaviour, it’s a fact, when printing a bead, this will swell and will also swell higher then the current nozzle depth. So when printing with one nozzle, the 2nd nozzle just bumps into this bead.

Nozzle lifting

There are two ways overcoming the nozzle collision:

  • Nozzle lifting
  • Exchangable print heads

Although multiple plint heads having some benefits, it’s also requires more automated print head exchanges and extra mechanical interfaces. That’s a lot of extra work.

Let’s review the current print head & see what could be done. The nozzle lifting switch could be done with the current X-axis. Moving the printhead against a ramp at one side, will lift one nozzle, moving against to other side, it lifts the other nozzle.

The lifting system is spring loaded (using existing heater springs) and the system requires something, so it’s not automatically jumping from one side to the other (during a retract): a simple cam plate is used for all this.

Dual extruder in action:

Marlin updatez

The dual material/color Cura slicing could still be used. When ever there is a new Cura update, there is no manual update necessary.

Instead changing the firmware (Marlin) is way more simple and it’s customized already, since it’s activialy using 2 extruder trains.

Now when ever it gets a “T0” or “T1” nozzle switch code, it adds some extra commands:

  • Increase temperature for first nozzle,
  • Lower temerature for second nozzle (just a constant),
  • Move to side of the printer, so nozzle lifting will happen,
  • Wait till final temperature is reached,
  • And continue printing.

Also the default homing & priming positions are a bit changed, so the printer is not colliding the print head against the switch system.

Testing

Printing multiple parts, including designing an ABC-character set for my new born son:

Download the STL files for this ABS-characterset: Cults3D.

Conclusions

This was a fun project, updating the current UM2+ into a dual material printer. It’s also a relative simple upgrade.

Ofcourse not all material combinations will adhere on top of each other. In my case it’s always PLA.

I’m not using this printer very often. A dual print takes often a bit longer and having a bit higher failure rate. But at least it’s cool possibility.

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