3D cellular structures should be the standard fill mechanism
used by slicing software.
My recent work has lead me to the conclusion that 3D cellular
structures make better fill patterns for 3D printing and that it would fit
neatly as the fill pattern used by slicing software. Using cellular fill will have benefits over using horizontal
alternating diagonal fills, and over 2D pattern fills such as hexagonal
tessellations.
Using cellular fill increases the strength of the part
relative to the amount of material. Conversely, less material is needed to
achieve the same overall strength. The cellular fill is a deliberate structure
with plastic used sparingly but in a focused way. Each cell is a pocket of
empty space with only the outer perimeter traced in plastic. This approximates
a sphere producing a strong shape relative to the amount of material used. Each
cell shares material with, and benefits from the stability and strength
imparted by other cells. Using less material leads to less printing time.
This work has been my attempt to contribute back to the Reprap
community. I have produced proof of concept model using the Pink panther woman
but I feel pressured to release this idea before I can get it fully operational
because of the recent plague of 3D patents and trolls.
In the near future, the use of cellular fill structures will
be a normal and automatic part of slicing software instead of the current zig-zag fill a cellular pattern will used. At each layer the slicing engine will also slice (or more likely compute) the
pattern and insert it into the object.
The generation of the pathways by slicing engines will also need to change. When
sliced horizontally an object filled with cellular structure looks like a
collection of different sized circles compressed together. For the best outcome, every cell needs to be
constructed as a series of complete circuits around the perimeter of the cell. In my experience, current slicing software tends to identify
some cells as complete circuits, while others are afterthoughts once the
complete cells are in place. The result is poor with the regions of the
afterthought cells not connecting correctly to one or both adjacent walls. To
date experimentation has been using objects filled with cellular structures
within the model itself.
Similar to the selecting layer height and print speed, the user will select the
pattern used, wall thickness and size of the pattern. Orientation
and location of the pattern may be advanced options. By varying the settings the desired strength,
density, and timing trade-offs can be controlled.
The main pattern of use is the truncated octahedron. It is a beautiful shape, made of six squares and eight
hexagons all with equal length sides. It is single shape that will completely occupy
3d space with no gaps. It tessellates through uniformly via translation
alone ie no rotations or other transforms. I have generated other more complicated patterns that could
be used but I don’t believe at this point that they offer any additional advantages.
Truncated octahedron pattern
This print is 100 * 100 * 50 mm and weight ~50gm.
It will support over 80kg placed on the thinner edge
I estimate it uses approximately the same quantity of plastic as a 10% zig zag fill
I estimate it uses approximately the same quantity of plastic as a 10% zig zag fill
The Pink panther woman, scaled larger and cut into six segments.
Each segment is filled with a different cellular pattern
Printed in transparent ABS to show off the internal structure
Individual segments can be seen in previous posts.
The truncated octahedron model will be made available soon.
