Theoretical and experimental investigations of the influence of overlap between the laser beam tracks on channel profile and morphology in pulsed laser machining of polymers

Pulsed laser machining is a method used for the fabrication of microchannels in different materials. There are various laser parameters and material properties which affect quality and dimension of the manufactured channel. The pulse overlapping is a process parameter which has significant effect on the resultant channel depth and morphology. In spite of many investigations on the effect of the pulse overlapping on laser machining, there is no theoretical equation for predicting the channel depth and profile, which involves this parameter explicitly as a function of the scanning velocity and the pulse repetition rate. In this paper, CO2 pulsed laser was used for the fabrication of channels in polymethylmethacrylate (PMMA). The temporal shape of the laser pulse and the corresponding overlap of each pulse over the spot area were added as two processing parameter to the theoretical equation. The influence of pulse overlapping on the morphology at the bottom of the channels is also studied. The results offer a simple way to predict the channel depth, profile and morphology for pulsed laser machining of polymeric materials which has good absorption at the laser wavelength.