Numerical investigation of thermal damage during laser drilling process

Abstract

Laser drilling is an advanced non-contact machining process which is a preferred choice in industrial applications due to its several advantages like precise hole, high positional accuracy, high repeatability etc. Geometry of the drilled hole like hole diameter and depth are important characteristics that greatly influence the quality of a drilled hole. In this work, a numerical model of transient heat transfer and thermal damage evaluation in Poly-methyl methacrylate (PMMA) material is presented using COMSOL Multiphysics®. Required material properties for the model are taken from available literatures. PMMA was selected due to its uniformity, isotropy, and the ease of characterizing its decomposition from solid to gas. A Gaussian heat flux is modeled and used as high energy laser beam. Ablation temperature of the material is considered as 698 k. The removal of material is modeled using deformed geometry interface module which is available in comsol multiphysics. After modelling, the parametric study has been done by varying laser power, beam diameter, and plater thickness to investigate about the thermal damage in terms of hole diameter and depth. To conduct the parametric study, central composite design (CCD) based design of experiment (DOE) has been generated using Design-Expert® software. 3D surface plots and contour plots are presented and discussed to illustrate the effect of input parameters on responses. It can be concluded from the results that laser power and spot diameter have a significant effect on drilled hole depth and hole diameter.