## Press-fit Geodesic Dome

September 16th, 2008Tags: fab, fablab, how to make almost anything, htmaa

Week 2: Make a press-fit kit out of cardboard.

An exhibit on Buckminster Fuller just ended at the Whitney in New York and served as the inspiration for this press-fit kit. Geodesic domes and spheres have been extensively used in architecture since their popularization by Buckminster Fuller.

The geodesic dome is constructed by starting with a icosahedron, and then modifying the sides through projection. The triangular sides of the icosahedron are split into smaller triangles, of which the corners are then projected to fit inside the sphere that subscribes the icosahedron. Depending on how many triangles are made to fit inside each icosahedron face, you get a better and better approximation of a sphere. I have chosen to construct a *3v* geodesic dome, which is called so because each vertice of the trianglular faces of the icosahedron is divided into 3. Practically, ths *3v* dome is made out of two different kinds of triangles which respectively form pentagons and hexagons.

First the size of the dome must be determined. This dome is 40 cm in diameter, which we can use to calculate the sizes of the triangles. Both types of triangles are equilateral with a base of length B or 8.07 cm. The triangles which will form the pentagons have two sides of length A or 6.972 cm, and the triangles which will form the hexagon have two sides of length C or 8.248.

The press-fit part of the kit should allow the user to slide the pieces of the dome together. To do this, the connector pieces were designed to be 0.75 cm deep and 0.38 cm wide. The cardboard itself is 0.4 cm thick, and to accomodate better sliding together of pieces, champers were added of 0.5 mm each.

The actually cutting of the cardboard was done with the universal laser cutter, at 40% power and 15% speed. The design first was adapted from Adobe Illustrator to Corel draw formats, which I have some tips on. The .SVG file that I used for cutting can be found here.