Optimization of Beam Intensity Profile in Surface―Cooled Laser Welding of Plastics―Improvement of Welding Depth by Using a Top―Hat Beam CO Laser―

In infrared laser welding of resins, surface-cooled and internally melted laser welding is effective for suppressing surface damage and achieving clean joints. However, in conventional welding using laser with a Gaussian intensity distribution, excessive heating at the beam center, where the laser intensity is highest, inevitably causes thermal degradation and limits the weldable thickness of the material. To address this issue, it is effective to optimize the laser beam intensity distribution, however, comprehensive optimization through experiments is time-consuming and costly. Therefore, in this study, thermal analysis was used to predict the temperature distribution generated within the material under laser irradiation with different beam intensity profiles, and the influence of the beam intensity distribution on the weldable thickness was investigated. Specifically, lasers with a Gaussian intensity distribution and flat top-hat intensity distribution were compared. Furthermore, welding experiments were conducted on PFA sheet materials using both beam profiles, and experimental validation was performed by comparing the weldable thicknesses achieved. An increase in weld depth was confirmed when using the top-hat beam.