Extended keynote paper of Eurosteel 2021 Automated production is finding its way into the fabrication of structural steel. One robot holds attachments (stiffeners, end plates, etc.) on a steel beam or column and another robot produces weld seams. However, welding robots can also be used for Additive Manufacturing (Wire and Arc Additive Manufacturing, WAAM). The wire electrode serves as a printing material. The Institute of Steel Construction and Materials Mechanics in Darmstadt is investigating how typical connecting elements for steel structures can be printed directly on steel beams using Additive Manufacturing with arc welding and robots. Furthermore, structural elements such as nodes for space frames can be printed and even complete structures, e.g. columns and a little bridge, have already been manufactured additively. The main focus is on determining suitable welding and process parameters. In addition, topology optimization is necessary in order to achieve good structures using a small amount of material. This is possible due to the free design prospects of WAAM, which opens up new design and production strategies.
Automated steel construction manufacturing with robots is becoming reality. The Institute for Steel Construction and Materials Mechanics of the Technische Universität Darmstadt has two welding robots. These robots are being used to assess various application for Additive Manufacturing. For the construction of steel, Wire + Arc Additive Manufacturing (WAAM) is suitable, which is similar to Gas-Shielded Metal Arc Welding. The wire electrode serves as printing material. With this method we can produce components in layers and achieve deposition rates of 5 kg/h. The components studied in this research project are connection elements such as simply supported girder connections and head plates, as well as reinforcing elements such as stiffeners and beam reinforcements. In this paper topology-optimized structures are presented, which can be printed with the WAAM directly on steel beams. First investigations on additive manufactured test specimens are shown.
Automated production is finding its way into fabrication of structural steel. One robot holds attachments (stiffeners, head plates, etc.) to a steel beam or column and another robot produces weld seams. However, welding robots can also be used for additive manufacturing (Wire + Arc Additive Manufacturing, WAAM). The wire electrode serves as printing material. The Institute for Steel Construction and Materials Mechanics in Darmstadt is investigating how typical connecting elements of steel construction can be printed directly on steel beams using Additive Manufacturing with arc welding and robots. Furthermore structural elements like nodal points are printed and even complete structures like columns and a little bridge have been manufactured additively already. The main focus is on determining suitable welding and process parameters. In addition, topology optimization is used to find good structures using a low amount of material. This is possible due to the free design prospects of 3D‐printing. This opens for novel design and production strategies.
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.
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