WAAM process for metal block structure parts based on mixed heat input

Additive manufacturing based on robotic welding is used for the manufacturing of metal parts by applying an arc as a heat source and wire as feedstock. The process is known as Wire Arc Additive Manufacturing (WAAM). However, the current WAAM process has a limitation in fabricating block structure components with high geometry accuracy and consistent welding due to the process complexity and lack of appropriate process planning method. Furthermore, common defects such as voids, gaps and collapse decrease the mechanical properties of the final product. This thesis presents a novel process planning method based on a Mixed Heat Input(MHI) strategy to minimise voids and collapse defects that occur in fabricating large block structure components while maintaining a high manufacturing efficiency. By dividing each layer into a boundary layer and multiple inner layers, the MHI method applies various heat input conditions at different positions of the layer allowing the construction of defects-free components. The performance of this method is shown by the fabrication of a simple structure component. To evaluate the mechanical properties of the deposited sample, the hardness and microstructure are exhibited and compared with the conventional WAAM process. Finally, the MHI strategy is applied to the manufacturing of a real-life large block structure component with a dimension of 670×465×154mm. The results show that such strategy succeeds in achieving production efficiency and quality simultaneously.