Influence of tool wear on internal damage in small diameter drilling in GFRP

In this study, drilled PWB is a type of glass/epoxy-resin GFRP, plain woven cloth, and thickness 1.6 mm (8 plies). This workpiece is the copper clad laminate. In experiments, the drills are the diameters of 0.4-5.0 mm. The holes are drilled under drilling conditions of spindle speeds of 20000-80000 rpm and feed rates of 10-50 mu m/rev. An amount of 30000 holes are drilled. The investigation is carried out from the view of the relationship between the internal damage around the drilled hole and the number of drilled holes. It is clear that drilling conditions are high feed rates to drill a great number of holes at a constant quality, and are low feed rates to drill a small number of holes at the high quality. Additionally, it is found that the ratio of the radius of the drill to the width of the yam is one of the important factors in estimating the tool life of small diameter drills. (C) 1997 Elsevier Science Ltd. All rights reserved.