This is a design for a small scale structural grid, geometrically composed by octahedra and tetrahedra - that make a rigid structure and pack space -, and physically/materially made out of 3d printed nodes and mdf laser cut bars (not in the first pic which corresponds to a test). There are two different kinds of nodes, that are named "chaser" (the hybrid sphere/polihedron one) and "ng" (the star shaped one), after two friends; the two nodes are "topologically" [?] identical; they can work in the same structure. The design of the nodes depart from 24 mm spheres (the diameter of the star is actually smaller after chopping it on 12 sides to place the cylinders and eliminating the original sphere; the bars have a length of 204 mm, which could be changed, and a cross section of aprox. 3x3 mm [3.2 mm width minus section lost by laser cut) to fit quite tight in the cylinders carved in the nodes (diam. 4.24 mm). The structure can take different shapes and grow in different directions. The one in the pics is made out of one octahedron, four "tetrahedra" and a free triangle; using eleven nodes. I designed it to print it in a makerbot, but am not getting good results yet. The pieces in the pictures are printed in a high end photo sensible resin 3d printer. It would be nice if someone could check the nodes in a makerbot...
Next step will be to parametrize the nodes so that they can be made larger or smaller with ease and/or change the section of the bars. Ok, this is already uploaded. It's a grasshopper definition [rather old software versions sorry: Rhino v 4.0 SR8 and Grasshopper 0.6.0059). Inside the file there are some explanation of the parametrization. The definition might be a bit clumsy but it is a beginner's effort. I am uploading an explanatory image, too.
Then i would like to parametrize the grid to be able to fill different volumes and than calculate the number of nodes and bars...
Another direction of development would be toward making larger nodes - for a larger structure - and using the 3d printed pieces for molding/casting in a functional material for this kind of use.
The pieces have been printed and cut at Fab Lab Sevilla, Spain, with the help of Juan Carlos Perez and Jose Buzon. Even if the geometry is rather simple, i have to mention that it is indebted with the workshops in geometrical grids taught by Prof. Antonio Saseta.
Print the nodes with a 3d printer. Cut the bars (barras cutting files) with a laser cutter in dmf of 3mm thickness. 6 nodes with 12 bars will make an octahedron. The bars (dxf) cutting file includes 12 bars. Additional nodes will make tetrahedra on each of the sides. Further octahedra and tetrahedra con be built going on adding bars and nodes in different directions.
Some of the jpgs uploaded explain the geometrical principles, that are easier to see in a drawing that to explain by writing.
Files uploaded include rhino files for the two nodes, stl files for the two nodes, and dxf file for the bars.
The grasshopper (parametric) file should allow you to play with the main dimensions of the thing (the node, not the bars).