An analytical model for laser drilling incorporating effects of exothermic reaction, pulse width and hole geometry

An analytical model is presented which incorporates the effects of using O2 as assist gas. The contribution of the enthalpy of oxidation used in the model was determined experimentally by capturing the ejected melt and measuring the volume percentage of oxidation. The formulation of recoil pressure used in the model takes into account hole diameter and depth, and the associated pressure variation. The model presented also considers pulse width which is shown to affect the drilling velocity. The model enables the prediction of the velocity of melt ejection, and the drilling rate, as well as the contributions of melt ejection and vapourisation to the overall drilling rate. The calculated drilling rates are in close agreement with the experimental results.