Numerical simulation and experimental research on reduction of taper and HAZ during laser drilling using moving focal point

Laser beam drilling has been widely applied in various industries due to its high efficiency and low cost. However, machining defects like obvious taper, heat affected zone (HAZ), and spatter may generate as hidden perils. In order to investigate generation mechanism of these phenomena and explore a proper solving method, a three-dimensional finite element model which describes the temperature field distribution and interaction between continuous laser and metal was put forward. Simulations on laser cutting with steady and moving focal point on carbon steel C45 workpiece with thickness of 1 and 4 mm were conducted. The comparison of hole morphology under initial simulation and experiments illustrated that the established finite element model is able to predict taper formation and size of HAZ in continuous laser drilling process. Moreover, using a moving focal point during laser drilling process is conductive to the reduction of taper and size of HAZ through contrast experiments. Both numerical simulations and experimental results indicated that the cylindricity and quality of deep holes can be significantly improved with a moving focal point.