Obayashi Corporation, one of Japan’s leading construction companies, has further underlined its reputation as a pioneer in the construction and architecture space, with the installation of the three-meter high metal 3D printed “the brænch” at its Technology Research Institute in Kiyose, Tokyo.
A portmanteau of branch and bench, the brænch is a continuation of the company’s quest to advance AM at construction scale. It follows its pioneering “3dpod” in 2023, claimed to be Japan’s first earthquake-resistant 3D printed building, and which was made with cement-based materials.
The brænch was delivered by a cross-disciplinary team with the aim of developing in-house expertise in Wire Arc Additive Manufacturing (WAAM). The process offers plenty of promise for the architecture, engineering, and construction (AEC) sector thanks to its greater deposition rates, lower material costs, and compatibility with large structural components.
Until now, WAAM’s application to construction‑grade carbon steel has been complicated – slag accumulation and print‑accuracy limitations have meant the process has focused more on non-ferrous metals. To tackle the associated issues, Obayashi developed a proprietary metal 3D printer that optimizes material combinations and welding parameters to eliminate slag formation and ensure stable, high‑precision deposition.
The result was structural members with high strength and excellent surface integrity, validated through extensive mechanical testing.
Manufacturing on Demand
The next step was to apply WAAM capabilities to expressive architectural form. A dedicated semi-automated design system was developed by Obayashi, that connects thousands of potential points in a design space to generate a network of printable paths that satisfy WAAM constraints, such as maximum overhang angle and minimum printable dimensions.
The system then performs structural analysis to optimize load distribution by eliminating inactive members. This gives a form that’s structurally coherent and digitally manufacturable.
The brænch’s structure was divided into 30 unique components, each printed individually using WAAM and hollow tubular steel elements to maximize strength‑to‑weight ratio while minimizing material use. The pieces were welded together on-site – augmented‑reality guidance helped achieve precise alignment of each geometry.
The top of the steel structure carries additively manufactured decorative parasols made from recycled polycarbonate, and produced by Tokyo-based firm DigitalArchi via robotic arm deposition (FDM).
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Author: Joseph Caron-Dawe
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