On-the-fly drilling with a fiber delivered face pumped laser beam

Abstract

A high power Neodymium:Yttrium-Aluminum-Garnet (Nd:YAG) Total-Internal-Reflection Face Pumped Laser (TIR-FPL) coupled with a fiber delivery system has been proven to be a powerful processing tool for On-The-Fly (OTF) drilling [1]. Single Pulse OTF drilling, (ie., one laser pulse per hole with continuous part motion) at shallow angles to the surface with material thicknesses up to 50 mils can be easily accomplished generating good quality holes. Optical sensors are used to determine laser pulse break-through time and are examined as a drilling process monitor. The OTF drilled samples are subjected to flow measurements to determine trends based laser parameters. The primary findings are that optical break-through sensors provide a viable monitor of optical system behavior to control the laser drilling process. The percent Break-Through Time (%BTT), defined as the ratio of the break-through onset time divided by the total laser pulse duration decreases with increasing joules per pulse. A generous 34% variation in the average flow/hole on the OTF drilled part can be obtained by controlling the focal point placement on the part and changing the laser energy per pulse. These data offer new insight into the characteristics and process capabilities of FPL/fiber delivered laser beams used in manufacturing applications.A high power Neodymium:Yttrium-Aluminum-Garnet (Nd:YAG) Total-Internal-Reflection Face Pumped Laser (TIR-FPL) coupled with a fiber delivery system has been proven to be a powerful processing tool for On-The-Fly (OTF) drilling [1]. Single Pulse OTF drilling, (ie., one laser pulse per hole with continuous part motion) at shallow angles to the surface with material thicknesses up to 50 mils can be easily accomplished generating good quality holes. Optical sensors are used to determine laser pulse break-through time and are examined as a drilling process monitor. The OTF drilled samples are subjected to flow measurements to determine trends based laser parameters. The primary findings are that optical break-through sensors provide a viable monitor of optical system behavior to control the laser drilling process. The percent Break-Through Time (%BTT), defined as the ratio of the break-through onset time divided by the total laser pulse duration decreases with increasing joules per pulse. A generous 34% variati...