Pressure-based indirect sensing of torch angular position in hand-held laser welding

Hand-held laser welding offers high flexibility and speed, but limited repeatability due to its strong dependence on a consistent torch-to-surface angle. This is critical in precision applications such as electric vehicle battery repair, where improper positioning compromises joint integrity. This study introduces a sensor-based method to indirectly monitor the torch holding angle (θ) by measuring shielding gas pressure at the nozzle outlet, building upon a patented mechanical design whose underlying pressure-angle relationship is quantified here. Numerical simulations demonstrate that gas pressure varies monotonically with θ and remains independent of axial rotation (β). Experiments conducted across four flow rates (15–30 L/min) and six torch angles (15◦–60◦) establish that a 5◦ angular deviation yields a pressure change of approximately 4 kPa at 30 L/min. This enables a theoretical resolution of 0.5◦ and a practical resolution of ∼ 1◦ using commercial sensors. Empirical transfer functions derived across these flow rates provide a robust, closed-form foundation for real-time operator feedback systems in advanced manufacturing environments.