In this work we study the effect of beam shaping on the melt pool free surface geometry of three different multi-kW high power laser-based processes, i.e. autogenous conduction welding [1] and deep penetration welding, and laser directed energy deposition using a metallic wire as feedstock. As dynamic beam shaping device, a newly developed deformable mirror withstanding up to >2kW laser power in c.w. was used and integrated into an industrial tool for laser materials processing. A coaxial high speed camera synchronized with a LED illumination system was used to capture images of the melt pool. An image processing algorithm was developed to automatically detect the melt pool free surface boundary contour. Although the deformable mirror allows producing a variety of different beam shapes, our study was limited to Gaussian-elliptical ones with various elongations and orientations with respect to the processing direction. Results achieved with such beam shapes were compared with the reference case of a circular Gaussian, finding that the beam shape significantly affects the area size, the width, and the length of the melt pool. Thus, this technology not only has the potential to adapt in real time the heat source to the workpiece geometry enhancing the efficiency of the energy transfer, but also can be used for automatic control to solve processing issues, like e.g. bridging the gap in autogenous butt-joint welding [2].

References

[1] Y. Mi, et al., Optics and Laser Technology, 2022, 148, 107718.

[2] Y. Mi, et al., Optics and Lasers in Engineering, 2023, 169, 107724.