Additive manufacture with graded bio-polymer composites

Bio-based materials are emerging a key alternative for carbon-intensive construction materials, which are becoming increasingly ill-suited to society’s ambitions to decarbonize construction. Beyond already established low carbon biomaterials such as timber, locally sourced second and third generation waste and side-stream biomass is recognized as having significant potential to be used in architectural elements. However, the use of these materials requires processing routes based in contemporary design and fabrication technologies. Additive manufacturing is one such route. This paper outlines an approach for graded 3D printing with a biopolymer-composite that incorporates local waste and agricultural side stream residues. In this paper, we describe the underlying motivations, challenges and opportunities for multi-material grading, and detail the development stages of a custom-built robotic tool and feeding system that enables continuous grading of two or three material inputs. Further, we explain the complications involved with material viscosity changes and the correlation to the design of the printing toolpath. We demonstrate the use of the custom-built robotic tool and feeding system on a set of architectural-scale weather screen panels, using different biopolymer mixtures and grading strategies.