Project 1 : Press - Fit Kit

When asked to create a press-fit kit, I wanted to create regular pieces that would combine in many different ways and would allow the construction shapes as complex as desired.

I have always been fascinated by the Platonic and Archimedean solids and wanted a construction kit that would allow me to build them. These solids all have edges of the same length, and each vertex are be connected to three, four or five edges at various angles.

The Platonic and Archimedean Solids

So I needed edges of only one length, but also vertices that could accomodate any angle of edge departure (within reason). Hence there are two degrees of freedom to accomodate for each edge at a single vertex. To accomplish this I started exploring possibilities on the program Antimony. I found two ways of creating degrees of freedom that I combined to design the project:

1. Creating many slots along a circular shape so as to allow one degree of freedom. Later on I made the slots a little larger on the outside so as to allow the edge to wiggle and take on several angles within one single slot.

2. Cutting only partly through the cardboard along the vertx pieces so as to create flaps that could fold at the desired angle. These fold marks are meant to be along the blue lines in the image below. These flaps provide a second and final degree of freedom needed.

Spiral Development

As discussed in class, my project development had a spiral shape after I tested a shape and improved the design.

My initial design had edge pieces parallel to the vertex pieces. I wanted to make three different layers that would be glued together:

• A plain layer
• A layer with a slot to fit onto the vertex semi-circle with a tooth that would fix the position of the edge
• A final layer with a hole that would allow a pin to go through it and the vertx in order to hold the whole joint together.

Unsurprisingly this design had many issues. First glue was required, which was against the idea of the assignment; Secondly, the tooth and the pin, both crucial parts of the joint, were to be made out of very thin pieces of cardboard, and so were very weak. Finally the three layers would have required the printing of many more pieces than necessary.

So I simplified the project and reduced the three layers to one that would fit perpendicularly to the vertices, hence removing the tooth and pin joint and settling for a stronger press-fit joint.

Several test prints were made in order to get several tricky parameters right: the width of the slots (which had to be very slightly under the width of the cardboard) and the power of the laser cutter at the places where the cardboard is meant to fold. I also added chamfers in order to make the joint come together properly.

When the parameters were right, I proceeded to cutting several pieces.

Here is the full kit!

I was unable to cut the pieces necessary to make all archimedean solids. For instance, the snub dodecahedron would take 150 edges and 60 vertices! I did however cut enough pieces to make more basic solids, including the Platonic solids, the cuboctohedron and even the snub cube.

Files

• Antimony file (version 1): Fit_and_push.sb
• Antimony file (version 2): Fit_and_push_v2.sb
• Image Export (5 joint): 5vertex_v2.png
• Image Export (4 joint): 4vertex_v2.png
• Image Export (3 joint): 3vertex_v2.png
• Corel Draw file: cutout.cdr

Tools used

• Antimony (stable version with .png export)
• Corel Draw
• Illustrator and the Harvard GSD Laser printing software
• Laser cutter (in the SEAS workshop, science center workshop, and GSD)