Product Code: ICAL05_M205

Optical Trepanning by Using Axcion Lenses
Authors:
Danyong Zeng, College of Optics and Photonics, University of Central Florida; Orlando FL USA
W.P. Latham, Air Force Research Labortatory, Directed Energy Directorate; Kirtland Air Force Base NM USA
P.F. Jacobs, Laser Fare Inc.; Smithfield NM USA
Aravinda Kar, College of Optics and Photonics, University of Central Florida; Orlando FL USA
Presented at ICALEO 2005

Percussion drilling and trepanning are two laser drilling methods. Circular laser spots are generally used in conventional laser drilling. Annular laser beams provide a new laser drilling mechanism. When an annular beam is focused on the workpiece surface, the material around the annulus laser spot is heated, melted, vaporized and removed, leading to the formation of a hole. This process, which we refer to as optical trepanning, does not involve any rotating optics or rotating workpiece. With geometric optics, a lens system using axicon lenses have been designed to transform a Gaussian circular laser beam into an annular laser beam. An analytical two-dimensional model was developed for optical trepanning. The analysis accounted for conduction in the solid, vaporization and convection due to the melt flow caused by an assist gas. Based on the model, the influences of pulse duration, laser pulse length, pulse repetition rate, intensity profiles and beam radius were investigated to examine their effects on the recast layer thickness, hole depth and taper. Experiments have been conducted on Inconel 718. Some geometrical and metallurgical characteristics during optical trepanning were investigated.