No abstract

3D printing or additive manufacturing (AM) is now becoming a common technology in industry. The research activities in this area are constantly increasing, because with the high level of automation and the possibility to produce individual and complex structures, the advantages of additive manufacturing are promising. Most materials used in the construction industry can be used for additive manufacturing, for example steel and concrete. The print head (for example, a welding torch in the AM of steel) is mainly led by industrial robots, whose movements must be transferred from the 3D geometry files to be manufactured. In contrast to all-in-one systems, where hardware, software and printed material are coordinated, most robot-based AM systems are made of components from different manufacturers and branches. The objects to be manufactured are complex and the manufacturing parameters, which significantly influence the geometry and quality of the manufactured part, are manifold. This makes the workflow from the 3D model to the finished object difficult, especially because it is almost impossible to predict the exact manufactured structure geometry or layer height (which would be indispensable for accurate slicing). During the manufacturing process, deviations between the target and actual geometry can occur. In this paper, parametric robot programming (PRP) is presented, which allows flexible motion programming, and a quick and easy reaction to deviations between target and actual geometry during the manufacturing process. Complex geometries are divided into iso-curves whose mathematical functions are determined by means of polynomial regression. The robot can calculate the coordinates to be approached from these functions itself. This allows a simple adjustment of the manufacturing coordinates during the process as soon as target-actual deviations occur. The workflow from the file to the manufactured object is explained. The principle of PRP is transferable and applicable to all robot manufacturers and all conceivable printing processes. In the following article, it will be presented using wire + arc additive manufacturing, in which welding robots or portals can be used to produce steel structures with high deposition rates. Furthermore, the project "AM Bridge 2019" is presented, in which a steel bridge was manufactured in situ over a little creek and the presented PRP was applied.

Der 3D-Druck ist in der Bauindustrie noch nicht etabliert. Das Potenzial dieser Technologie hinsichtlich Individualisierung und Automatisierung lässt jedoch die Möglichkeit der Anwendungen im Bauwesen erkennen [1]. Darüber hinaus ist mittelfristig mit einem verstärkten Fachkräftemangel zu rechnen, was für eine stärkere Automatisierung spricht.

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.

Wire Arc Additive Manufacturing (WAAM) is a welding process used to build up three-dimensional structures in steel. Like other Additive Manufacturing technologies, it allows for geometrically-complex structures to be fabricated which are otherwise unfeasible to manufacture using traditional methods. This research paper presents an integrated design approach to the use of WAAM in the context of large-scaled applications, focusing on column variants of gradually-increasing geometric complexity as basis for architectural constructions. It combines material behavior and process para-meter research together with a rudimentary digital twin model, with the aim of providing a digital tool to design architectural structures for WAAM. To achieve the desired geometries, necessary welding parameters are stored and applied to the digital twin model. This is complimented by multiple process-control checks, which are implemented during the printing process to ensure that an object is generated as planned. Finally, the structures are manufactured and are subjected to a critical evaluation in order to identify the possible future potential. The challenge of combining geometric complexity with manufacturing for large scale represents a next step in the integration of WAAM in steel constructions for architectural applications.