How does a flat sheet of material, like plastic or an airtight textile, become an inflatable structure with a three-dimensional shape? The traditional process involves creful design with a lot of trial and error in order to place seams between two or more sheets. That involves a lot of labor, so a team of engineers from the Hasso Plattner Institute developed a new machine called AirTied which can automatically fabricate inflatable structures.

AirTied structures consist of tubular inflatable trusses, which are just flat sheets folded over with the edges welded. Without the machine’s intervention, that material would produce one very long cylinder when inflated. But the AirTied machine can form those tubes into 3D structures by placing knot-like nodes in specific locations, like a clown making balloon animals for kids at a party.

The material comes from a single spool, but AirTied can produce up to five parallel trusses at any time. It accomplishes that by rotating the spool to one of five slots that can either fold the tube or crimp it with a wire tie to create a node. It can, for example, crimp two trusses together in their middles to create an X-shaped structure. The machine controls the lengths of the trusses between nodes by folding each truss over until they’re all ready for crimping.

An Arduino UNO Rev3 board manages that process and the coordination of the motors using a modified version the popular GRBL CNC firmware. That lets it run G-code generated by the AirTied software, which helps users easily and quickly design structures by specifying the lengths of trusses and positions of nodes. The software even estimates the total cost of materials required for a particular structure.

That cost is quite low and the demonstrates the primary advantage of AirTied: its ability to automatically fabricate affordable structures at speed unmatched by other techniques.