Effect of Laser Pulse Overlap on Machined Depth

This paper studies the effect of laser pulse overlap on machined geometry. A model was created to predict the laser machined geometry based on baseline data and the exact placement of laser pulses. Pulse overlap was varied and the predicted geometry was examined. To validate the model, experimental channels were created on D2 steel with an Nd:YVO4 picosecond laser at a wavelength of 532 nm. Step height and surface roughness values were studied for each channel. Good correlation was found for pulse overlap up to 75%, after which heat accumulation and deposition effects became more dominant. SEM images were taken of the channel cross sections to observe melt zones. The results indicate that pulse overlap of 75% provides a relatively smooth surface finish with minimal heat and redeposition effects. A second comparison between experimental and simulated geometry was completed on silicon to assess the model's ability to predict geometry for nonmetallic materials. Good agreement was found. Published in the Transactions of NAMRI/SME, Vol. 38, 2010, pp. 291-298.