Despite modern timber construction being on the forefront of digital technology in construction, subtractive CNC-fabrication technologies are still predominantly used in the industry. An important break in the digital chain occurs when prefabricated small building parts have to be assembled manually into functional modules. This can result in a loss of digital information in the process. Therefore, a robotic setup for timber construction was specifically developed by the authors enabling large-scale spatial fabrication possibilities using a combination of subtractive external tools for cutting and drilling and additive robotic operations. Through automatization techniques and innovative feedback processes, the system can minimize material waste by reacting to different material sizes even during the construction process. In a case study, which was undertaken in the course of the Master of Advanced Studies program in Digital Fabrication at ETH Zurich, a complete digital workflow using additive robotic fabrication processes in timber construction was realized. We demonstrate the conception of the worldwide first double-story robotically assembled timber structure, explain its fabrication processes including an integrated envelope, and conclude by analyzing the robotic fabrication technologies in terms of their efficiency and structural and functional capabilities and limits.

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The demand for building materials has been constantly increasing, which leads to excessive energy consumption for their provision. The looming environmental consequences have triggered the search for sustainable alternatives. Mycelium, as a rapidly renewable, low-carbon natural material that can withstand compressive forces and has inherent acoustic and fire-resistance properties, could be a potential solution to this problem. However, due to its low tensile, flexural and shear strength, mycelium is not currently widely used commercially in the construction industry. Therefore, this research focuses on improving the structural performance of mycelium composites for interior use through custom robotic additive manufacturing processes that integrate continuous wood fibers into the mycelial matrix as reinforcement. This creates a novel, 100% bio-based, wood-veneer-reinforced mycelium composite. As base materials, Ganoderma lucidum and hemp hurds for mycelium growth and maple veneer for reinforcement were pre-selected for this study. Compression, pull-out, and three-point bending tests comparing the unreinforced samples to the veneer-reinforced samples were performed, revealing improvements on the bending resistance of the reinforced samples. Additionally, the tensile strength of the reinforcement joints was examined and proved to be stronger than the material itself. The paper presents preliminary experiment results showing the effect of veneer reinforcements on increasing bending resistance, discusses the potential benefits of combining wood veneer and mycelium’s distinct material properties, and highlights methods for the design and production of architectural components.

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Additive manufacturing (AM), as resource-efficient fabrication processes, could also be used in the dimensions of the construction industry, as a variety of experimental projects using concrete and steel demonstrate. In timber construction, currently few additive technologies have been developed having the potential to be used in large scale. Currently known AM processes use wood in pulverized form, losing its inherent structural and mechanical properties. This research proposes a new material that maintains a complete wood structure with continuous and strong fibers, and that can be fabricated from fast-growing locally harvested plants. We describe the material technology to create a solid and continuous filament made of willow twigs and investigate binding and robotic AM methods for flat, curved, lamination, and hollow layering geometric typologies. The resulting willow filament and composite material are characterized for structural capacity and fabrication constraints. We discuss our technology in comparison with veneer-based lamination, existing wood filament printing, and fiberbased AM in terms of fabrication, material capacity, and sustainability. We conclude by showing possible applications in the construction industry and future research possibilities.