Researchers at the Zurich University of Applied Sciences have created a toolhead mod for Prusa Research’s MK3 printer that prints 90° overhangs without support material.

They have built a 4-axis printhead that rotates at -90/+90°. The best part? The design files for the toolhead are entirely open-source. So if you want to build your own RotBot 4-axis non-planar 3D printing tool, head over to Printables for the files.

Stefan from the YouTube channel CNC Kitchen visited a lab in Switzerland, where the RotBot toolhead was designed to understand how it works. The video has some interesting technical details, so it’s worth watching.

Research and limitations

An academic paper in Advances in Additive Manufacturing Technology explains more about how RotBot achieves those curves and overhangs.

The researchers Michael Wüthrich, Maurus Gubser, Wilfried J. Elspass, and Christian Jaeger explain that the quality dramatically decreases in FDM printing once the overhanging exceeds 45-60°.

This RotBot is unique because: “In contrast to the conventional FDM printer, where the layers are in a plane, with this new concept, the layers become cone-shaped. This results in the combination of the 45° rotated plane and the vertical rotational axis.”

The team had to develop a new “conical slicing” technique to teach the printer to print with the new RotBot toolhead. You can find the details of this in the video from CNC Kitchen and in the research paper.

One of the positives of this type of toolhead is that it reduces waste from support structures. However, with this approach, you can only slice conically; therefore, the perfect 90° overhangs are always downwards. If you want to print an overhung outward slope, you’ll still need to print a support structure.

Still, there seems to be a lot of enthusiasm for this concept and questions about whether the new “conical slicing” could go mainstream.