Study Of Acoustically Controlled Laser Drilling Technology

Laser machining processing is a high technology related to lots of branches of sciences and technologies, such as optics, machinery, electronics and computer, laser drilling is one of the old applications of laser machining processes. Yet many issues remain to be solved when high quality holes are to be drilled in various materials today. Because of laser drilling speed and quality is effected by the changing in laser's focus position, reflectivity and laser peak value power. Therefore, laser power, pulse width, laser focus position and some other parameters should be set differently to drill different materials with high quality and speed.The objective of this Dissertation was to study digitally controlled laser machining system for diamond drilling for wire drawing dies, on the basis of study and theoretical analysis of physical mechanism for laser drilling process.The investigations performed in this Dissertation were focused on the time dependence of audible sound signals under laser beam and material interaction, developments of a high frequency Q-modulation method using ultrasound and a acoustically controlled laser drilling system in combination of computer.1. We introduced the development situation of laser drilling technology at home and abroad. And we analyzed theoretically the laser drilling physical process, in which detailed considerations of the material temperature increase, formation of melt, vaporization and introduction of recoil pressure under the condition when materials are exposed to the laser beam. An innovative solution was proposed in diamond drilling for wire drawing dies.2. To improve further the drilling speed, an innovative improvement was performed at laser resonator, the use of a high frequency of ultrasonic vibration in total reflection mirror enables Q-modulation frequency in laser resonator up to 150 kHz, high laser peak power pulses were obtained at 200 W and it meets the requirements of laser drilling process.3, We found this sound signals represented drilling process and concluded that drilling process could be controlled using sound signals, whereas infrared signals met control requirement of the process, through the study of phenomena of sound produced in laser drilling and analysis of massive data of experiments and graphs, and methods to improve drilling speed were proposed according to material properties.4, Bringing together all our research data, an acoustically controlled laser drilling system for special purpose was developed in combination of computer. On the basis of on-line detection of acoustic transducer and process schedule, this system controlled the worktable movement so that the laser focus can be put on a so correct position, this method makes laser drilling process precise and quickly. The method has not reported yet. Lots of experiments showed good results at diamond drilling for wire drawing dies.A future improvement of this method was proposed in the end of this dissertation.