Open-source co-extrusion hot end shows new way for waste-free multi-material 3D printing

Developer Roetz has introduced a new approach to multicolor printing that does not require prime towers or material waste. His “Roetz-End” is a self-developed, openly licensed co-extrusion hot end that is manufactured from aluminum using selective laser melting (SLM). The component combines four filament feeds in a single outlet, enabling direct co-extrusion in the hot end itself—rather than at the nozzle tip, as is common with conventional multi-material systems.

What makes the Roetz-End special is the way the material is deposited. Four filaments are heated simultaneously and extruded together without mixing completely. Instead, clearly defined color segments are created within the strand. Which color ends up on the outer perimeter edge depends on the direction of movement of the print head. This allows models with specifically colored surfaces and clear transitions to be produced – such as cubes with different colors on each side.

Printing at certain angles can achieve partial mixing of the filaments. This creates soft color gradients, as Roetz shows in a demonstration video. Precise control of these effects opens up new possibilities for artistic or functional applications, such as decorative objects or visually coded components.

However, the system in its current form is not a complete alternative to multi-material units (MMUs). It is less suitable for printing different materials – such as soluble support structures – and instead focuses on multi-color or multi-component filaments such as PLA. In combination, however, this could lead to the creation of new material composites that combine flexible and rigid areas in a single component.

Roetz has published his development as an open-source project on YouTube and GitHub. In doing so, he wants to ensure that the concept is considered “prior art” and cannot be patented.