Horizontal spans cannot be 3d printed without support structure underneath. However, traditional support structures like flat pieces of corrugated steel or plywood would take away the geometric freedom of 3d printing.
In this project, we explore fabric as a support structure, it naturally form finds complex doubly curved surfaces, enabling a truly unique architectural expression.
The process is to first erect a fabric formwork (tensile structure), then 3d print on the fabric, and finally remove the fabric infrastructure to reveal the resultant 3d printed structure.
A large anthropomorphic manufacturing robot was utilized to 3d print large prototypes on a fiberglass mesh fabric. Our team designed a custom 3d printer that could be attached to the tool end of the robot. This allowed us to test our ideas at a larger scale than is permissble with traditional desktop 3d printers.
The custom 3d printer consists of the hardware needed for extruding the material: dual extruder nozzle, driver kit, driver motors, fans, ect. It also consists of the electronics necessary to operate the 3D printer: power transformer, arduino, power distribution, bread board. All of this was designed to interface with the Kuka robot platform, and synchronize with its movements.
The 3d printer needs a way to know about the fabric formwork's location and geometry. We designed a custom Contact Based Scanning method, and built our own hardware and software to implement it.
A physical probe contacts the surface and then the coordinates of the contact are recorded using the cartesian coordinates of the 3D printer. After scanning an array of these points, they can be used to construct a digital twin of the fabric formwork.
In traditional 3d printing, an object is built up using ubiquitous horizontal contours for manufacturing simplicity. The use of a fabric support structure allows us to instead orient the fibers to optimize structural performance and material usage.
Each layer has its own design driver, metrics, and structural analysis to determine the final design. While each layer is designed for a unique problem, they work together to form a cohesive structure.
Most of the layers are designed for structural performance, but others are designed to improve the fabrication process.
Two design approaches were evaluated for their efficacy in resolving a uniformly distributed gravitational load: Stress Line Based Design and Force Flow Based Design. Finite Element Models were built using Karamba, then four metrics were used to compare the designs: Max Normal Force, Max Bending Force, Max Shear Force, and Max Displacement. Averaging all metrics, the Force Flow based design performed 28% better.
The final prototype is 2500 square centimeters and 50cm tall. The total waste is limited to 400 square centimeters of fabric with no waste 3d print material (PLA). The print time was 16 hours long, but if the same structure were to be printed using conventional methods, it would take 94 hours to print and it would produce waste PLA 3x the weight of the product itself. After careful evaluation of our method, fabric formwork still seems like a promising option for full scale construction.