A comprehensive review of solid-state friction stir processing robots: Design, dynamics and control for enabling applications in additive manufacturing

Abstract

Solid-state friction stir processing underlies both the solid-state joining of Friction Stir Welding (FSW) and the layer-by-layer material deposition of Friction Stir Additive Manufacturing (FSAM). FSW, a plastic-deformation-based bonding technique, has gained widespread adoption across aerospace, automotive, and other fields. By leveraging plastic deformation to achieve metallurgical bonding, FSW circumvents critical defects inherent in fusion welding processes, such as thermal cracks and porosity. FSAM, emerging as a transformative extension of FSW, enables layer-by-layer solid-state fabrication of complex three-dimensional (3D) structures. FSW/FSAM robots have emerged as critical solutions to overcome the rigidity limitations of traditional machine tools through their flexibility and intelligent integration advantages. This paper introduces the FSW/FSAM processes and comprehensively reviews recent advancements in FSW/FSAM robots, systematically categorizing the research progress into three key domains: equipment integration architectures, dynamics, and control. Combined with the emerging field of FSAM technology, it further discusses existing technological challenges and proposes future development trajectories for FSAM robotic systems, offering a theoretical framework and a technological roadmap for advancing the engineering implementation of FSAM in intelligent manufacturing.