Fiber laser cutting of steel materials with twin spot beam-twin spot setting in kerf width direction

In laser cutting, the temperature distribution would have significant influence on cutting characteristics, and the intensity distribution of a laser beam has a possibility to improve the cutting quality. In this study, a fiber laser beam of Gaussian distribution was divided into two beams by a roof axicon lens, and the cutting characteristics were investigated by using the twin spot Gaussian beam setting in the kerf directions. The cutting experiment of a cold-rolled steel plate with a thickness of 3.2 mm was carried out by a 3 kW fiber laser with a nitrogen assist gas, and the Gaussian mode of 114 μm spot and the twin Gaussian mode of two 110 μm spots were used with the variation of power ratio in twin spot processing. At the exit side of kerf by the twin spot process, the width of the cutting front in the low intensity side became wider than that in the high intensity side, and the dross could be reduced in the low intensity side due to sufficient ejection of the molten metal from the front wall rather than the side wall of kerf. The twin spot process could reduce the dross height below 18 μm in the low intensity side, which is smaller than that by the single Gaussian beam process.