The team at the Human Computer Interaction Lab from the Hasso Plattner Institute in Potsdam, Germany lead by Phd researcher Robert Kovacs developed a construction system using plastic bottles and 3d-printed connections. Karamba was used to analyze the structure’s displacements and stress distribution in its load-bearing components.

TrussFab is an end-to-end system allowing users to fabricate and study large-scale structures using plastic bottles and 3D-printed connections, making them easy and quick to construct. When building large structures, it is not only about scale and print volume, but rather the main design objective is typically to withstand large forces. Large objects afford substantial external loads; furniture, bridges, and vehicles, for example, must all be engineered to hold the weight of a human. Designing for large forces, however, requires substantial engineering skill from envisioning appropriate structures in the first place to verify their structural integrity.

The Trussfab editor is available as a plugin to Sketchup, in which the embodied engineering knowledge within the program allows users to validate their designs using the integrated structural analysis. Trussfab’s Sketchup editor offers primitive building blocks in tetrahedron and octahedron shapes and special tools for tweaking them. This enables Trussfab’s users to maintain the truss structure and the overall structural stability of the design at all times. After a structure is designed, Trussfab generates 3D model files of all the necessary connection hubs for each node, which users can then send directly to a 3D printer. Unique IDs will be embossed into the 3D-printed pieces for clarity, allowing users to then assemble their structure using standard sizes of plastic bottles.

To make sure that the designed structures are not only stable, but can also bear the desired load, users compute the forces acting inside the structure. First, the software looks for flaws in the truss structure, i.e., it searches for parts that are not completely locked in place by other members and are subject to shearing forces or bending moments. The software suggests placing additional stabilizing members should these be required. Secondly, the software checks whether the structure will carry the applied load and marks the bottles in red and blue shades accordingly.  For this step TrussFab uses the integrated finite element analysis engine Karamba3D.

At the recent Human Computer Interaction conference CHI’17 in Denver, the team constructed a Trussfab pavilion designed by architect Oanh Lisa Nguyen Xuan, which was 5m high and consumed  1268 bottles and 191 3D-printed hubs. The pavilion took about 6 hours to assemble on site.

Text and Images by Robert Kovacs. Contact Robert Kovacs to try TrussFab for free.