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Multi-material 3D printing has caught on in a big way, but the volume of waste that accompanies some popular multi-material systems is ever-present in the conversation. Not so for Heinz Löpmeier, whose self-developed “rotating mixing nozzle” has resulted in a multi-material 3D printing system without the need to purge.

Posted on Reddit, where he goes by the username sophier, Löpmeier’s design runs on Marlin, and maps specific colors to nozzle angles by leveraging a Python script in Blender. It’s capable of full and slight color changes, as well as “halftoning”.

“The idea came first when printing with regular mixing nozzles, which don’t fully mix but create a toothpaste effect,” Löpmeier told All3DP. “The effect looks quite cool in itself, and is the same reason why duotone filaments became quite popular, I think.”

Löpmeier’s first attempt at controlling that effect was with a printer that rotated its build plate to change the filament’s color. It allowed for infinite rotations, but the build plate’s movement resulted in much slower prints than the design’s current iteration, which rotates the nozzle and twists the machine’s Bowden tubes in the process, unwinding during travel moves.

While he developed the design with the rotating build plate just two years ago, Löpmeier has been experimenting with mixing nozzles for six. That was also when he began using Blender and its Python API, wrote a G-code importer, and began testing direct path manipulation in lieu of slicing software. He then wrote the “nozzleboss” add-on for Blender – for which there is a robust GitHub repository – that enables him to export paths from inside Blender.

“One big advantage of this approach is that you have all of Blender’s modeling tools and painting tools to modify the path. You can even use the sculpt mode to sculpt the G-code file or paint a flow multiplier map with gradients and all directly on the toolpath,” he said.

Löpmeier’s recent Reddit post ends with a dash of cultural commentary – “PS: inb4 any patents! ;)” – a jab that could read as aimed at Statasys’ recent patent infringement lawsuits against Bambu Lab that happens to, in part, targets the latter’s use of purge towers.

Still, there may be some seriousness to the claim; the nozzle mixer itself is certainly innovative, with a patent-worthy design that seems ripe to be plucked by some ambitious party with capitalistic visions for its future. Perhaps that someone could be Löpmeier. Then again, perhaps not.

“Probably not worth the effort,” he said. “Ain’t nobody got time for that.”

To see Löpmeier’s rotating nozzle mixer in action – and for more commentary regarding its build and design – you can check out the Reddit post that caught our interest. Then, be sure to visit and follow his Instagram and X profiles, which contain many examples of multicolored prints, as well as photo and video documentation of the nozzle mixer itself.

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License: The text of "This ‘Rotating Mixing Nozzle’ Doesn’t Need To Purge While Multicolor 3D Printing" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.