Theoretical and experimental investigations for geometrical error during hemispherical cavity machining on CO2 laser

Abstract

CO2 laser material processing has become popular due to its unique advantages such as high productivity, ease of automation, non-contact processing, greater material utilization, and minimum heat-affected zone. Polymethylmethacrylate (PMMA) is found to be one of the most suitable thermoplastics for CO2 laser machining due to its higher melting point and higher absorptivity at the CO2 laser wavelength. The scope of the present work deals with geometrical error analysis during machining of the three-dimensional spherical cavity with the help of a 2D setup of the laser. The influence of process parameters like power, cutting speed, and the number of passes of laser probe on cusp height is examined. The cusp height is measured after machining equal and unequal step size on PMMA. The experiments were performed for profile controlled approach for equal step size and accuracy approach for unequal step size. An algorithm is proposed for predicting unequal step diameter with a constant value of cusp height. It was observed that higher power, lower speed, and more number of passes of laser probe leads to minimum cusp height. Hence, the proposed algorithm for predicting unequal step diameter for a constant cusp height leads to a reduction in staircase effect, thereby, producing a smoother curve as compared to the profile controlled (equal step diameter) approach.