Optimization strategies for robotic additive and subtractive manufacturing of large and high thin-walled aluminum structures

Wire and arc additive manufacturing (WAAM) based on gas metal arc welding (GMAW) is a potential technology for fabricating large-scale metallic structures due to its high deposition rate, high energy efficiency, and low cost. It can produce near net-shape components by depositing metallic material layer by layer using a welding process. This paper presents a robotic additive and subtractive manufacturing system. In manufacturing large and high thin-walled structures, a critical issue is the unevenness of the layers. The accumulation of layers with poor flatness leads to significant differences in the heights of different positions in a layer, making it unable to continue the multi-layer material depositing process. The objective of this research is to investigate optimization strategies for manufacturing large and high thin-walled metallic structures with the robotic additive and subtractive manufacturing system. Three optimization strategies are proposed to obtain flat layers, including deposition with weaving, arc igniting and arc extinguishing control, and local measuring and milling strategy. Experiments were designed to explore the effect of these strategies. The experimental results show that the combination of these strategies can improve the surface flatness of layers, reducing the differences in the heights of a layer. Using these strategies, a large and high thin-walled component is manufactured, demonstrating the potential for fabricating large metallic parts in a very short time by the robotic additive and subtractive manufacturing system. Besides, regression models were generated for establishing the relationship between process parameters and bead geometry in deposition with weaving.