Robotic Non-sequential Interlocking Assemblies

Timber is increasingly considered as an alternative to other structural materials, such as steel and concrete, allowing to reduce the environmental impact of the construction industry. However, it often becomes waste at the end of its service life because it is challenging to recover from buildings due to the use of non-reversible connection systems. Friction-based form-fit assemblies, such as wood-wood joints, offer a potential solution for creating reversible assemblies of structural members. Non-sequential assemblies, a novel type of joint within this category, are primarily locked by their kinematics and require much less friction for their stability than sequential assemblies. However, manual assembly of such joints is challenging due to the necessity of moving elements with high precision, particularly when size and weight of elements increase. Multi-robot assembly processes provide a solution to this challenge by enabling non-sequential assembly of multiple elements through synchronized motion. This paper presents an integrated design and fabrication workflow for the design and (dis-)assembly of non-sequential timber structures using two synchronized industrial robot arms. This includes the generation of the joints according to structural information, their detailing, the definition of feasible assembly sequences, the generation of the robotic instructions and the execution of synchronized assembly using two small-scale robot arms. A case-study of the design and fabrication of a 1:1 scale triangulated frame structure is presented. The aim is to demonstrate the feasibility of synchronous (dis-)assembly using multiple robots and highlight the potential of non-sequential assemblies for reversible structural systems in architecture.