Wire- and arc-based additive manufacturing (WAAM) is a promising technology for large-scale additive manufacturing of metallic components. However, due to the high heat input by the electric arc, interpass cooling time decelerates the average manufacturing speed. Since future applications aim to the production of large structural steel components, the manufacturing speed is a key parameter to make WAAM usable for civil engineering. Within the scope of this paper, different process cooling strategies are weighed up against one another with regard to efficiency, impact on the process, as well as to the influence on the microstructure of the processed steel. For the thermal evaluation, welds on vertically placed plates were performed using the gas metal arc (GMA) process. As far as different cooling methods are concerned, the standard GMA process is carried out with water bath cooling, high-pressure air cooling and also with aerosol cooling. Temperature curves were determined using thermocouples which are dipped into the molten pool. The evaluation of the microstructure and the hardness is carried out by means of cross sections and Vickers hardness tests. The results show that aerosol cooling can be a promising addition to WAAM as it can be applied during welding and is capable to modify the t_8/5 time and, therefore, the mechanical properties of the steel.

Wire and arc additive manufacturing (WAAM) is one of the most promising technologies for large-scale 3D printing of metal parts. Besides the high deposition rates, one of the advantages of WAAM is the possibility of using in situ alloying to modify the chemical composition and therefore the material properties of the fabricated workpiece. This can be achieved by feeding multiple wires of different chemical compositions into the molten pool of the welding process and generating a new alloy during the manufacturing process itself. At present, the chemical composition is changed stepwise by keeping the wire feed speeds per layer constant. This article describes the possibilities of generating chemically graded structures by constantly alternating the wire feed speeds of a multiwire WAAM process. This enables the chemical composition to be smoothly changed during the printing process, and generating structures with highly complex material properties. Several material combinations for different possible applications were successfully tested. Furthermore, grading strategies to avoid negative influences of low-ductility intermetallic phases were examined. The results show that low-ductility phases may even have a beneficial influence on the fracture behavior if they are combined with ductile phases. Moreover, prospective possible applications are discussed.

Changing process conditions such as distortion, varying seam preparation or gap width during welding is a major challenge in automated gas metal arc welding (GMAW). While human welders can adjust the process during welding (e.g. welding speed, torch orientation), an automated welding system needs sensors to detect and actuators to adjust the process. Adjusting the process in response to changing process conditions is usually referred to as adaptive welding. The aim of this work is to build a robotic welding system capable of automatically adapting the welding process using some of the approaches of a human welder. To enable adaptive process control, a robotic welding system is built. It consists of four main components: a six-axis industrial robot for mechanical guidance of the welding torch, a welding power source, a monochrome visual camera as an image sensor and a process controller that combines the three components. The camera captures images of the weld pool during welding and processes the images to provide geometrical information such as the width of the weld pool and the position of the weld pool front. Changes in the weld pool geometry are quantified, and an adjustment strategy is generated in the process control unit in real time. Process adjustments can be mechanical (e.g. welding speed, torch orientation) and electrical by adjusting synergic process settings (wire feed speed, arc length, process dynamics). Validation tests demonstrate the functionality of the welding system. Two use cases were investigated. Firstly, a deposited weld bead was examined, and variations in the width of the weld pool were induced by varying the welding speed. The second application was a seam tracking application. The path is pre-programmed, and the specimen is positioned with an offset to the path. Compensation for the offset is implemented.

The classic 3D printing of metallic components using powder bed processes has so far mainly been used in the aerospace industry or in mechanical engineering. For the production of large structural components, such as those used in steel construction, laser powder‐based additive manufacturing processes are too expensive. Wire and Arc Additive Manufacturing (WAAM) can offer a possibility to realize 3D printing of large steel components. This process, also known as “shape welding”, has become interesting for the building industry in combination with flexible robot technology and low energy welding processes. This is not only because of the vast variety of design options, as digitalisation and integration into computer‐supported design, planning and manufacturing processes also open up new possibilities for steel construction. Additionally, WAAM is also well‐suited for the production of load‐optimised components in particular. This study describes the current and future fields of application, the characteristics of production and the load‐bearing capacity of the achievable component types.