Adaptive laser beam shaping with a deformable mirror for gap bridging in autogenous butt joint welding

One challenge in laser beam welding is the variability in joint gaps encountered during autogenous welding of butt joints. This study therefore develops and evaluates an adaptive laser beam shaping technique that utilizes a deformable mirror. By integrating image processing and an adaptive Kalman filter, the proposed method provides real-time estimation of the gap width which varies from point to point along the joint. This capability allows for dynamic adjustments of the beam shape during processing through feed-forward control. Proof of concept was performed in welding sheet metal plates with stepwise changes in gap widths, up to 0.55 mm. The distortion of the welded parts and the topology of the weld seam were assessed both qualitatively and quantitatively using data from a laser line scanner. The data analysis revealed a reduction above 80% in workpiece residual distortion compared to conventional welding with a static circular beam shape. Additionally, welding quality at a 0.55 mm gap width met the laser welding standard (ISO 13919-1) level D. In contrast, approximately 10% of the measured points using a static circular beam did not meet the level D of this standard. The seamlessly integration of real-time gap measurement with adaptive beam shaping thus offers a promising solution to mitigate gap variability in laser beam welding of butt joints. This approach also highlights the broader potential of adaptive beam shaping in high-power metal processing.