In-Process monitoring and adaptive control in 100 W fiber laser welding

Abstract

A fiber laser is easily applied for micro welding owing to the excellent beam quality. Furthermore, a fiber laser is expected to be a promising heat source for adaptive control since the peak power is variable within sub-micro-second period. The objective of the research was to develop a new laser system with inprocess monitoring and adaptive control for the stable production of sound welds in thin sheets. The bead-on–plate welding of 0.1 mm-thick stainless steels was performed with a 75 W fiber laser beam of 1,090 nm wavelength. The stability of bead widths of laser welds made with or without monitoring and adaptive control was investigated in welding the sheet on the plate with a hole which should affect heat conduction and transfer. It was revealed that the heat radiation signal was sensitive to the increase in the bead width according to the change from heat transfer process to heat-insulated process. Moreover, the peak power was adaptively controlled in the minimum 50 ms-short period in order to produce stable weld bead width regardless of the existence or absence of the heat transfer plate. Consequently, it was confirmed that the fiber laser was an excellent oscillator for laser micro welding as well as for adaptive control.A fiber laser is easily applied for micro welding owing to the excellent beam quality. Furthermore, a fiber laser is expected to be a promising heat source for adaptive control since the peak power is variable within sub-micro-second period. The objective of the research was to develop a new laser system with inprocess monitoring and adaptive control for the stable production of sound welds in thin sheets. The bead-on–plate welding of 0.1 mm-thick stainless steels was performed with a 75 W fiber laser beam of 1,090 nm wavelength. The stability of bead widths of laser welds made with or without monitoring and adaptive control was investigated in welding the sheet on the plate with a hole which should affect heat conduction and transfer. It was revealed that the heat radiation signal was sensitive to the increase in the bead width according to the change from heat transfer process to heat-insulated process. Moreover, the peak power was adaptively controlled in the minimum 50 ms-short period in order to prod...