In–process monitoring and adaptive control in micro lap seam welding with fiber laser

Abstract

The objective of this research is to obtain fundamental knowledge of in-process monitoring and adaptive control for fully-penetrated welds in micro lap seam welding of 0.1 mm-thin titanium sheets with a 100-W single-mode fiber laser. In these welding conditions aiming conventionally and adaptively at the formation of a stable bead on the bottom surface, when welding speed decreased, the weld was changed from keyhole-type to heat-condition-type penetration, which led to generate partial-penetration. Therefore, it was investigated how the penetration change had an influence on in-process monitoring and adaptive control for full penetration. With respect to the monitoring, it was revealed that heat radiation signal was sensitive to the change in weld bead width on the both surfaces except for the width on the bottom surface during expansion to the stable size in the heat-condition-type weld. As for adaptive control, the peak power was controlled according to the heat radiation signal measured during the weld bead expansion in heat-condition-type welding. As a result, a full-penetration weld was produced regardless of penetration type. These results revealed that laser adaptive control on the basis of in-process monitoring signals was beneficial for micro lap seam welding with a continuous wave (CW) fiber laser beam.The objective of this research is to obtain fundamental knowledge of in-process monitoring and adaptive control for fully-penetrated welds in micro lap seam welding of 0.1 mm-thin titanium sheets with a 100-W single-mode fiber laser. In these welding conditions aiming conventionally and adaptively at the formation of a stable bead on the bottom surface, when welding speed decreased, the weld was changed from keyhole-type to heat-condition-type penetration, which led to generate partial-penetration. Therefore, it was investigated how the penetration change had an influence on in-process monitoring and adaptive control for full penetration. With respect to the monitoring, it was revealed that heat radiation signal was sensitive to the change in weld bead width on the both surfaces except for the width on the bottom surface during expansion to the stable size in the heat-condition-type weld. As for adaptive control, the peak power was controlled according to the heat radiation signal measured during the weld...