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Non-planar slicing, explained
In short
Non-planar slicing generates toolpaths on the part's surfaces instead of intersecting the model with flat horizontal planes. Every point of the path carries a nozzle orientation — usually the surface normal — so orientation is a continuous field that drives both rotary axes. Extrusion rates adapt where surfaces tilt, and the slicer must check collisions between nozzle, part and machine in five axes. The output is still G-code, but with rotary-axis words on most moves, so ordinary 3-axis firmware cannot run it.
A conventional slicer intersects the model with horizontal planes and emits flat perimeters. A non-planar slicer instead generates toolpaths on the part's surfaces: offsetting paths across the geometry, assigning each point a nozzle orientation (usually the surface normal), then checking the whole motion for collisions between nozzle, part and machine.
- Orientation is a field, not a setting — it varies continuously across the part and drives both rotary axes at every moment.
- Extrusion must adapt — layer thickness and flow change where surfaces tilt and converge; flat-slicer flow maths doesn't carry over.
- The output is still G-code — but with A/B (rotary) words on most moves, which is why ordinary printer firmware can't run it.
- Support logic inverts — instead of propping up overhangs, the slicer re-orients the part so overhangs become printable walls.
This is why the software, not the frame, is the field's bottleneck — and why slicer collaboration is half of what we do.
Questions this page answers
Can Cura or PrusaSlicer generate non-planar toolpaths?+
No. Mainstream slicers intersect the model with horizontal planes and emit flat-layer G-code with no rotary-axis moves. Non-planar toolpaths require surface-based slicing — paths generated on the part's geometry, with orientation and collision checks in five axes.
What does a non-planar slicer actually output?+
Still G-code — but with A/B rotary words on most moves, because each point of the path carries its own nozzle orientation. That is why ordinary 3-axis printer firmware cannot run it.
Why is slicing considered the bottleneck of 5-axis printing?+
The mechanics of a fifth axis are comparatively simple; generating collision-free, well-oriented curved toolpaths on arbitrary geometry is an open algorithmic problem. Hardware without toolpaths is furniture, which is why slicer development and collaboration dominate research in this field.
Last updated: November 2026