Dual-stage process control for plasma arc additive manufacturing of Ti-6Al-4V — Addressing variable bead geometry and wire melting in continuous deposition

This paper presents a dual-stage process control strategy for Wire Arc Additive Manufacturing (WAAM) of Ti-6Al-4V, targeting two key challenges in continuous deposition: variable bead geometry and wire melting stability. The proposed method integrates predefined bead width and height planning with height control along the tool path and incorporates real-time power adaptation through vision-based feedback and process limit handling. A novel anti-windup scheme addresses power constraints to prevent wire stubbing and maintain melt pool stability, particularly in complex or small-scale geometries prone to overheating. Intra-layer proportional control of plasma current enables precise width adaptation based on real-time visual feedback. Experimental validation across multiple builds, including a non-uniform layer height workpiece featuring overhangs up to ±60◦ , demonstrates improved dimensional accuracy and enhanced deposition stability. The results highlight the potential of the proposed control architecture to enhance reliability and precision in wire-based additive manufacturing of Ti-6Al-4V components. The final workpiece is an ultra-high vacuum (UHV) chamber and was tested in a qualification procedure. The results of the procedure confirm the feasibility of the process for UHV applications.