Form{less}
Robotically Thermoformed Molds for Concrete Casting
Mackenzie Bruce + Gabrielle Clune
Instructors: Tsz Yan NG + Wes Mcgee
Sponsor: SOM Chicago
Form{less} focuses on the creation of complex thin-shell concrete forms using robotically thermoformed plastic molds. Typically, similar molds would be created using the vacuum forming process, producing direct replications of the pattern. Creating molds with this process is not only time and material intensive but also costly if customization is involved. Thin-shell concrete forms often require a labor-intensive process of manually finishing the open-face surface. The devised process of thermoforming two nested molds allows the concrete to be cast in between, with finished surfaces on both sides. Molds made with polyethylene terephthalate glycol (PETG) allow the formwork to be reused and recycled.
The research and fabrication work include the development of heating elements and the creation of the robotic process for forming the PETG. The PETG is manipulated via a robotic arm, with a custom magnetic end-effector. The integration of robotics not only enables precision for manufacturing but also allows for replicability with unrestricted 3-dimensional deformation. This research aims to develop a process that allows for the creation of complex geometries while reducing the amount of material waste used for concrete casting. The novelty of the process created by dynamically forming PETG allows for quick production of formwork that is both customizable and replicable. This method of creating double-sided building components is simulated at various scales of implementation.
The devised modified vacuum forming process uses a jig to create surface conditions without directly replicating the pattern below. The resulting cast required no post finishing, creating a porcelain finish to the concrete.
PETG is attached to the frame and pulled by using the magnetic end effector. The robotic arm enables unrestricted three-dimensional deformation challenging if not impossible through other processes. The resultant thin-shell concrete cast demonstrating the incredibly thin edge condition achievable through this process.
The devised setup of the thermoforming process included the creation of heating elements, a rigid frame, and magnetic end effector. Steel picked up by the magnetic end effector creates the interior dimension of the formwork. The exterior dimension of the formwork is formed by offsetting the PETG creating nested molds determining the thickness of the concrete. The two thermoformed molds are attached to a frame, suspending the cast. The casting process includes a rigid frame to suspend the PETG formwork. Concrete is added to the exterior mold. The interior mold is then placed on top using sand to maintain the structure of the mold.
