Research Of Laser Drilling With Long Pulsed And Acoustic-optical Q-Switched Laser

The laser as optical tool in the21st century, has been widely used in the field ofindustrial processing since its birth in short few decades ago.Because of its prominentadvantages, laser drilling is widely used in the tiny holes processing such as aviation turbineblade cooling hole, automobile engine nozzle, surgery pinhole and so on. Lamp-pumpedpulse laser output is a sequence of spikes which is beneficial to small hole processing, but asa result of relaxation oscillation phenomena, the laser energy distribute in each peak pulses,reducing the peak power. A sequence of inerratic pulses can be obtained after usingacousto-optic modulation in lamp-pumped pulse laser, this article aims at the research oflaser drilling with long pulsed and acoustic-optical Q-switched laser.Firstly, the changes of pulse peak power, pulse energy and pulse width withdifference modulation frequency were analyzed base on the theory of Q-switch. Accordingto the interaction of laser and materials, the heat transfer process of the absorbed laser energyin the metal surface and internal were analysed, as well as the influence of the generation ofplasma on the processing. According to the literature, the laser drilling process is dividedinto three stages, and establishes a general model of laser drilling.Finally, laser drilling experiment on1mm iron plate has done using the laboratoryhomemade long pulsed and acoustic-optical Q-switched laser. The difference in drillingquality and processing efficiency was analysed with unmodulated long pulse laser andmodulated long pulse laser, and find that the sequence of inerratic pulses can obtain betterpass quality, higher machining efficiency by contrast. At the same time, analyzes the effectof drilled holes under different modulation frequency, and the result shown that15KHz canachieve good pass quality. In addition, the influence of defocusing and laser energy ondrilling quality has been experimental analyzed.