So far, the only publicly shared experiment on performing non-planar 90° overhangs has been conducted by Rene K. Mueller, an expert in the field of 3D printing. He published his results on XYZ dims, a site dedicated to detailed research into both software and hardware aspects of 3D printing.

The research is fairly new, as Rene himself started the work in January 2021. What inspired him to try and code his own conic slicer for performing non-planar overhangs is the concept of a rotary angled nozzle, originally developed by the Zurich University of Applied Sciences (ZHAW).

Instead of trying to copy that rotating nozzle concept, Rene decided to attempt similar conic shapes with a vertical nozzle. But again, because of the physical limitations of such a nozzle, he simply made his cones less steep, ensuring that the nozzle wouldn’t crash into the cone while printing. Following several iterations of his experiment, he eventually made it work.

Slicing in Non-Planar Mode

The concept of printing 90° overhangs with a non-planar 3D printing setup is an interesting one. It’s possible, but the slicer’s algorithm needs to be modified first.

Rene created his own algorithm for Slic3r, which provides the ability to print in non-planar mode. He included multiple variables which the user can change, depending on what the 3D printing setup looks like. The modified slicer can be downloaded for free from GitHub. If you’d like to try it out for yourself, you can visit a more detailed guide on how to set it up.

The algorithm is set to generate G-code for a 4-axis rotating nozzle setup by default, but it can easily be changed to work with a conventional 3-axis belt 3D printer. Here, we’ll focus on how a 3-axis printer can achieve non-planar overhangs.

The idea behind making non-planar overhangs is to have the edges of layers slope downwards, forming either a conic or tilted 90° overhang.

Conic Overhang

A conic overhang slopes downwards from all sides, creating a mushroom-like shape. The main limitation with making conic overhangs is the cone angle. Because many printers have fans around the nozzle, they will eventually get into the way and crash into the cone if the angle is too steep.

During his research, Rene concluded that a cone angle of 15-25° is optimal. If you go higher, more problems occur both in terms of hardware limitations and decreased print quality: Because the nozzle stands vertical while printing angled layers, it runs over them, thus decreasing the quality.

Again, 3D printed non-planar overhangs are still in an early stage of development, so quality isn’t the main concern. The technique will definitely improve as more experiments and slicer modifications are made.

Tilted Overhang

Tilted overhangs are geometrically simpler than conic ones because they’re made in a single direction. Print quality is slightly better here, but it’s important that the angle is kept up to around 25° to keep it safe. The extrusion rate is also important, since it dictates whether or not the top surfaces will be smooth or rough. The exact value is quite dependent on the printer and can require a few test prints to get right.

Adjusting the Printhead

As we’ve already mentioned, non-planar 3D prints on a 3-axis 3D printer require clearance from the nozzle and the rest of the printhead. The parts that are usually sticking out are the vents that help with cooling. Removing these vents does indeed improve clearance, but the lack of cooling can cause a decrease in print quality.

It remains to be seen what solutions will come for this issue. For now, each printhead needs individual mods, since they’re all different sizes and shapes.