Theoretical And Experimental Studies On Laser Drilling Deep Holes By Superposed Pulsed Lasers

Laser drilling is widely used in manufacturing industry for its advantage of high-speed, high-efficiency, high-precision and low-cost process. Laser drilling holes in the thick metal plate needs a large amount of pulse energy. It usually interacts with the material for a long time with long pulse laser which affects the quality of holes. Short pulse laser machining has a good precision while the drilling speed is relatively low. Aiming at the different characteristics of the long pulse drilling and short pulse drilling methods, also for economical drilling, a superposed pulsed laser drilling method has been put forward. Studies on laser drilling deep holes in the thick metal plate have been conducted theoretically and experimentally.Firstly, the physical change of metal materials during laser drilling has been analyzed. Based on the interaction between laser and material, the reason and influencing factors of material's physical change has been studied in details. Laser drilling results under different laser parameters and material properties have been discussed. The laser drilling methods have been classified according to the different mechanisms of material removal.The physical model of superposed pulsed laser drilling has been established, and the material's thermal effect under different laser parameters has been analyzed. The role of long pulse and short pulse in superposed pulsed laser drilling has been clearly put forward respectively based on their characteristics. The laser drilling results in long pulse alone drilling and superposed pulsed laser drilling have been simulated, which provides a theoretical basis for the selection of laser parameters.The laser drilling experiment has been performed in 5mm-thick 304 stainless steel with two Nd:YAG lasers. By changing the laser parameters, such as pulse energy and pulse width, the relating effect of drilling velocity has been studied. All the results have been compared to the results by long pulse alone drilling. It is shown that the superposed pulsed laser drilling can effectively improve the drilling velocity and drilling efficiency, which provides a guide in laser parameters matching for application.The drilling quality has been studied on the thick 304 stainless steel, the effect of laser parameters such as pulse energy and pulse width on the size and quality of the hole has been analyzed, laying the foundation for high quality laser drilling.