Abstract
Laser drilling may improve by proper selection of the laser parameters. One of the important parameters in laser hole drilling is the focus setting of the focusing lens. In the present study, the effect of the beam waist position on the resulting hole exit/entry diameter ratio is investigated experimentally. An Nd-YAG laser is used to drill the holes in stainless steel and mild steel sheets at different thicknesses. The study was conducted to include the physical processes involved at different beam waist positions during the drilling operations. It is shown that altering the beam waist positions tends to produce converging and diverging hole walls for negative and positive positions respectively. The drilling improves at a certain beam waist position for a given workpiece thickness.