In custom space frame structures, the design and construction of joints present a significant challenge. The objective of this project is to provide a tool that generates joints for multiple edge connection scenarios. It gives controlled user interaction on material choice, cross-section size, and the shape of joints. Loads at connections from the self-weight of the structure are factored in determining the topology of each joint. We take a classic computer graphics algorithm, the Marching Cubes, and turn it into a fabrication solution for this project.
We developed the project as a C# plugin for Grasshopper. The code first analyzes a set of wireframe bars and places it into a graph data structure, taking into account the radius of each bar according to user input. Then we calculate the angle of the incoming bars and assign a custom length to each joint. The next step is to implement the marching cubes algorithm at each node to generate an equipotential surface according to the grid density. The 3D grid of density values is then augmented or subtracted according to the structural results produced by the structural simulation software Millipede outputs and a refined surface.
One potential use of the tool could be to turn any mesh model from Google’s 3D Warehouse into a human-scale deployment with PVC pipes as low-cost linear elements and 3D printed joints as the custom solution for n-number of bars meeting a joint.