An Introduction to Non-Planar 3D Printing

Many 3D printing processes exist today, such as fused-filament fabrication (FFF)/fused-deposition modeling (FDM) and masked stereolithography (MSLA). But almost all 3D printers in use today are planar, which means they don’t really move in three dimensions. While it is complicated to implement on a practical level, non-planar 3D printing is possible. To help you understand how it works, CNC Kitchen took a tour of the 3D printing lab at the Zurich University of Applied Sciences and got a first-hand look at their non-planar 3D printing research.

In this context, “planar” refers to the fact that most 3D printers really work in 2.5D. Any movement in the XY plane is possible, but 3D printers do not extrude or cure material with moves in the ZX or ZY planes. This is because 3D printers work by laying down a series of cross-sectional layers to form a 3D object. If those layers are thin enough, they aren’t even visible to the naked eye. But what if an FFF 3D printer could extrude while moving in the ZX and ZY planes (all three axes at once)? That’s non-planar 3D printing and it comes with interesting challenges and benefits.

There are two reasons that most 3D printers are planar: because it prevents collision between the part and the extruder/hot end assembly, and because it simplifies slicing software algorithms.

It is impossible to completely solve the first problem, because there are always part geometries that create areas where the extruder can’t reach without collision — especially when dealing with overhangs. But the addition of a fourth axis to rotate the hot end reduces the problem. When combined with 3D slicer paths, the university was able to use a rotating head for non-planar printing that works for a wide range of part shapes and sizes.

The slicing software for this printer is interesting, because it is an extension of Simplify3D. Instead of conventional 2D slices (planes), it produces conical 3D slices. They’re conical to give the rotating hot end clearance. The hot end sits at a 45° angle, so a cone with walls 45° or shallower is safe. The rotational fourth axis lets the hot end move so that it is always perpendicular to the current print surface.

This isn’t trivial to set up and it does have limitations, but it offers some benefits over planar 3D printing. The most obvious is that it can eliminate layer lines—or at least traditional layer lines. It can also print some parts faster than a planar 3D printer can. And though gravity is still a factor, it can handle some overhang geometry better than planar printers do.

We probably won’t see printers like this in the consumer market any time soon, because it doesn’t offer many practical benefits. But a printer that could switch between planar and non-planar modes would offer the best of both worlds with slicing software sophisticated enough to take advantage of it.