Vibrating-lens-assisted laser drilling

Abstract

Laser ablation is a viable technology for the manufacture of deep holes in a variety of industrial applications. Therefore, approaches need to be sought that increase the efficiency of these processes. In the current work, a hybrid processing method that utilizes superimposed vibrations to increase the depth of the produced holes will be addressed. The rationale for using vibrations is to change the energy distribution of the laser beam during the process. To this end, the traditional and the vibrating-lens methods were studied from the energy distribution standpoint at locations along the sensitive direction of the laser beam in drilling processes. Comparing the fluence with the ablation threshold of the laser beam to remove the material, the reasons why the vibrating-lens method is more effective in drilling deep holes were explained through theoretical analysis. Then, a new structure for the generation of lens vibrations along the sensitive direction using a PZT actuator for vibrating-lens assisted picosecond laser processing based on simulations was designed. Finally, different parameters were used to drill holes in stainless steel by the traditional and the vibrating-lens assisted methods, considering the frequency of the vibrations, dwell time and defocusing distance. The results have shown that the vibrating-lens method can improve the depth of the holes up to 60 % compared to the traditional method at the same dwell time. Therefore, it improves the efficiency of the deep hole drilling process.