## Introduction

In order to take advantage of **4- and 5-axis** **non-planar FDM**^{1)}** printing** (e.g. tilted, conic, cylindrical, spherical) the model may be segmented and then dedicate slicing methods can be assigned to such sub-volumes.

A few basic examples **combining planar and non-planar slicing** methods on sub-volume segmented models illustrating the possibilities printing without support structures:

- Fused Deposition Modeling (FDM) also known as Fused Filament Fabrication (FFF)

## T-Model: 2 Segments: Z-planar & Conic

Utilizing novel conic slicing as introduced by ZHAW researchers in 2020/2021:

Conic slices can be printed with 4-axis Rotating Tilted Nozzle (RTN) although printing the Z-planar sliced part might not give goods surface results but rather using a 5-axis Penta Axis (PAX) printhead to cover both cases easily.

## T-Model: 3 Segments: Z-planar & 2x Tilted

Using non-rotating but tilted sliced (like used with belt-printers) but in two distinct directions:

Tilted slices can be printed with 4-axis Rotating Tilted Nozzle (RTN) but the first Z-planar part, as mentioned above, might not provide sufficient surface quality, whereas a 5-axis Penta Axis (PAX) printhead can print both segments easily.

## T-Model: 3 Segments: Z-planar & 2x X-planar

A more classic planar approach but with different planes as reference, first Z-planar then twice X-planar in different directions:

X-planar printing requires either 5-axis Penta Axis (PAX) printhead or the ability to tilt the bed.

## Overhang In/Out: 2 Segments: 2x Conic

Lower part is sliced with **conic slicing** with **inside-cone** mode to print in-going overhang, whereas the upper part is sliced with **outside-cone** mode to cover the out-going overhang:

This model covers the classic case of 4-axis Rotating Tilted Nozzle (RTN) application: rotating 45° tilted nozzle printing in two different modes (outside-cone and inside-cone); a 5-axis Penta Axis (PAX) printhead also can print such.

## Overhang Out No 5: 2 Segments: Z-planar & Conic

Another overhang piece, stretching out into one direction; the lower part Z-planar, and the overhang conic (outside-cone mode) with an offset to align better with the lower segment:

*2 segments: planar (bottom), conic with center offset (top)*after z-planar switching to conic (outside cone), conic center align with lower segment conic part reaching edge of lower segment full height of overhang segment extending the overhang further *conic part asymmetrically extending*conic parts reached all horizontal model limits finishing up the segment finished piece

## Overhang Out No 5: 3 Segments: 2x Z-planar & Conic

Perhaps a more realistic approach using the conic part as a “balcony” just for the overhang part sufficiently thick to carry next segment and switching back to Z-planar:

*Overhang Out No 5 model segmented into 3 sub-volumes: z-planar first, then conic (outside-cone) building a thin “balcony” as support for the z-planar part on top again*

Early tests have shown the thickness of the conic overhang “balcony” depends on the actual length of the in-air overhang, where print speed, part-cooling capacity and extrusion consistency determine the geometrical accuracy.

## Conclusion

Unlike with ordinary Z-planar slicing, it may be suitable to dedicate a particular slicing method and orientation for sub-volumes in order to take advantage of the possibilities like avoiding support structure, particular strength properties or surface quality.

This of course opens a wide-range of possibilities and complexity therefore:

- where to segment
- which slicing method to use
- in which orientation the slicing is performed

but I think it’s worth it, in particular when a piece is printed more than once like with small series manufacturing / production.

The examples have been produced with various slicers and combined with a new application coordinating the segmenting and dedicated slicing methods, which currently (2021/04) is in development; it also involves a new file-format describing the segmenting and its slicing settings. The segment positioning was done manually as a start, but I expect with more experience and research some cases can be detected automatically.

Sub-volume segmenting is just one approach to take advantage of 5-axis FDM printing, another is continuous slicing along the form.

## References

- [Coyetaux, Crook, Pauwels, Whelan] 5-Axis 3D Printing (2018) – free paper (PDF)
- [Wuethrich, Elspass, Bos, Holdener] Novel 4-axis 3D printing process to print overhangs without support material (2020) – non-free paper (PDF)

## See Also

- 5-axis Penta Axis (PAX): development overview with more references
- 4-axis Rotating Tilted Nozzle (RTN): development overview as well
- Non-Planar Slicing with Planar Slicer, more groundwork for slicing non-planar

PS: All animations I combined in a short 3min video: Mixing Planar & Non-Planar Slicing Methods for 3D Printing Overhangs without Support Structure (YouTube)