MULTIPLE REFLECTION EFFECTS ON EVAPORATIVE CUTTING WITH A MOVING CW LASER

Multiple reflection and beam guiding effects during laser machining are analyzed numerically. The surface of the treated material is considered to reflect the laser irradiation in a fully diffuse fashion, limiting the analysis to bodies that have a rough surface during laser evaporation (e.g., micro-explosive removal, violent surface boiling, etc.). For local irradiation calculations the material surface is divided into a number of triangular elements with linear interpolation functions. The net radiative flux for these elements is obtained from standard view factor theory. The irradiation calculations are combined with a simple integral method governing conduction losses into the medium, and the resulting groove shape and depth are found through an iterative procedure. Considering multiple reflection results in increased material removal rates and deeper grooves, accompanied by a flatter profile near the centerline and steeper slopes in the other parts of the groove cross section.