3D Printing: Sub-Volume Segmenting & (Non-)Planar Slicing

Table of Contents

Introduction

In order to take advantage of 4- and 5-axis non-planar FDM¹⁾ 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:

*2 segments: z-planar, conic* (outside-cone)

T-model segmented into 2 sub-volumes, sliced z-planar and conic (outside-cone mode)

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:

T-model segmented into 2 sub-volumes, sliced z-planar and twice tilted in opposite 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:

T-model segmented into 3 sub-volumes, sliced z-planar and twice x-planar

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:

*bottom: inside-cone, top: outside-cone*

Overhang in/out model segmented into 2 sub-volumes: lower part is sliced conic (inside-cone mode) and upper part conic (outside-cone mode)

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)*

Overhang Out No 5 model segmented into 2 sub-volumes: z-planar at the bottom and overhang segment conic (outside-cone mode)

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:

*3 segments: planar (bottom), conic (middle) and planar (top)*

*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. More examples with “balcony” printed with 3-axis FDM printer followed.

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.

*solely z-planar sliced, support structure required using 3-axis FDM printer*

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)

XYZ dims *

3 Dimensions Explored – 3D-Modeling & 3D-Printing