A study of affecting parameters in the laser hole-drilling of sheet metals

In practical applications of laser drilling the quality of the drilled hole is the critical factor, and recently methods of studying the influence on quality of the main process variables have been developed, which seek to improve quality rather than to explain the drilling mechanism. Hole quality can be judged by: the internal form and taper and related geometrical features, and the extent of heat-affected material. The optimum performance in laser drilling depends very much upon the proper selection of the laser parameters as well as upon the physical properties of the workpiece material. With so many variables, and with incomplete knowledge of the relationships between them, statistical methods are needed to design experiments and to analyse the results. In the present work five factors at four levels have been considered: four factors are given quantitatively; one, the material specification, is given qualitatively. The result is that the design has four blocks identified with materials, each of which can be treated as a complete factorial design. However, the materials can be described quantitatively by their physical properties, so that the results have been correlate with groups generated by dimensional analysis. It is observed that main effects of laser parameters as well as their interactions, have significant effects on all features of hole geometry. Drilling-medium pressure has been found to be a very effective factor, since its interactions with the other parameters in any order are significant.