Continuous-wave laser drilling assisted by intermittent gas jets

Abstract

We describe a study of the laser drilling of stainless steel (SUS304) using a fiber laser with a wavelength of 1090 nm, assisted by intermittent gas jets. By comparing with the results obtained with the conventional continuous gas jets used in assisted laser drilling, we demonstrate that the use of the intermittent gas jets can effectively increase the material removal rate and reduce the consumption of assist gas. The intermittent gas jets can be modulated according to the frequency to effectively reduce the overcooling effect of the assist gas. Experimental results show that both the drilling depth and machining quality can be greatly and simultaneously improved. Two types of intermittent gas jets, namely, straight and swirling jets, are considered, and the effects of the intermittent frequencies and gas pressures on the laser drilling are investigated and discussed. We conclude that the intermittent gas jet method greatly reduces heat loss and slag formation around the hole exit in the laser drilling process. Compared with the results obtained when using a continuous straight gas jet, laser drilling with a 20-Hz intermittent straight gas jet reduces the drilled hole entrance diameter and increases the drilled hole depth by a factor of up to 1.7. The intermittent gas jet method can reduce the quantity of assist gas being used, and therefore the cost, especially when expensive gases such as helium and argon are being used.