Introduction: Sea Urchin Origami
This origami structure was designed by Simon Schleicher. It is based on a traditional diamond pleating technique and explores the possibility to fold an initially flat, punctured plane back on itself and create a closed sea urchin-like shell structure.
For more information about Simon Schleicher and his research and teaching on bio-inspired design and fabrication, please visit www.designinnovation.berkeley.edu
Step 1: Equipment & Material
To produce this intricate origami structure, I recommend the following materials and equipment. If you want to make it fully by hand, you would need a cutting matt, cutter, ruler, pencil, tape, and a glue to secure the folding in the final condition. In my case, I used the additional help of a cutting plotter, which allows me to produce origami patterns faster and test designs alternatives based on shorter iteration cycles. The machine shown in the picture is the KNK Zing Orbit 15.
For the material of the origami folding, I recommend a paper or foil that is sturdy enough to withstand a bit of wear and tear. A good choice, for example is the Canson® 1557 paper with a weight of 120-160 g/m². In general, the Canson® 1557 is a light grain, acid-free paper suitable for studies, sketches and drawing. It is 100% alpha-cellulose, containing no wood fiber. Stock and surface-sized it withstands repeated erasing or folding and will not flake. I chose it also because of its pure white color.
For the further processing, I cut it into 11"x11" pieces.
Step 2: Generating Custom Patterns
If you want to get started right away, please check the attached file “SeaUrchinOrigami_SimonSchleicher.” It is a letter sized pdf with the crease pattern for this origami structure. The color coding acts like an instruction and tells you whether a line is a mountain fold (blue), a valley fold (red), or represents a line that needs to be cut (green).
If you are interested in learning more about how I made this pattern, please check the other files attached. In general, this origami structure is based on a ring-shaped geometry, referred to as “annulus”, and is defined by two concentric circles. The crease pattern is created by subdividing both circles into a series of points and cross-connecting them to each other in certain way. In my studies, I found that a good ratio between inner and outer circle is between 0.225 - 0.3. While the folding would also work for other ratios, this one is particularly suitable to allow the structure to nicely close back on itself.
To test variations of this pattern and to see how slight changes will affect the folded shape, I made a pattern generator and folding simulator in the software Rhinoceros & Grasshopper. The pattern generator is included in the attachment and is purely based on Grasshopper and allows to manipulate the two defining circles and the symmetry of subdivision. To test the folding, I used the Grasshopper plug-in Kangaroo Physics, which is a live physics engine developed by Daniel Piker and allows to interactively simulate, form-find, and optimize structures under consideration of pre-defined constraints.
Step 3: Fabrication
The first step in the fabrication of the origami pattern is setting up the cutting plotter. The KNK Zing Orbit 15 has a small drag knife that can be controlled in x.y, and z direction. For this project, I used the Standard Material Detail Blade and the standard blue blade holder. The screw at the end of the blade holder allows you to adjust the blade’s position so that its tip is hardly sticking out. Once mounted, the origin for the file is set to the corner of the paper. In the software Make the Cut, you can then adjust force and speed for each cut. For my project, I work with two main settings. The creases were done with a Blade Offset of 0.35mm, Speed 17, and Force 2, while the cuts were done with a Blade Offset of 0.35, Speed 17, and Force 25. As a result of these settings, the crease pattern is only lightly scored into the pattern and allows for easy folding.
Step 4: Folding Sequence
After creasing and cutting the pattern, we can start with the folding process. There is no particular order that needs to be kept. However, I found it the easiest to start with the mountain folds first and after that the valley folds. To bring the folding closer together and to slowly start contracting the origami pattern, one can gradually pinch the corners, which will intensify the folding. This needs to be repeated so long until the outer perimeter comes together at a point and the outer edges start to touch each other. Finally, to secure the origami structure in this stage, one can glue or tape the edges to each other.
Give it a try, it is lots of fun!
Step 5: Final Models
All models were designed by Simon Schleicher and built from a single sheet of paper.
If you want to find out more about Simon's work on flexible structures and the projects that he and his students did at the University of Stuttgart and UC Berkeley, please check the video attached. Happy folding!
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