Additive manufacturing of a bridge in situ

Nominated for Eurosteel 2021 Best Paper Award
Additive manufacturing (AM) is playing an increasing role in the production of complex steel structures. Robot- or machine-guided gas-shielded metal arc welding (GMAW), known as wire and arc additive manufacturing (WAAM), is suitable for this purpose. A small footbridge was designed in shell form at TU Darmstadt. It was completely additively manufactured over a stream on site using a welding robot. The work called for cantilevered manufacturing without support structures, which poses special challenges in manufacturing. This paper describes selected aspects of this project: the preliminary strength studies, the manufacturing strategy to ensure homogeneous manufacturing and the findings from on-site manufacturing. In addition, investigations were carried out which led to a notable increase in the deposition rate with the right choice of gas and wire.