Effects of Tool-Edge Form during the Drilling of CFRP

摘要

The drilling of carbon fiber reinforced plastics (CFRP) involves many problems, such as an extremely short tool life or CFRP delamination occurring at the exit surface of the drill. In an effort to solve these problems, experiments were performed to observe the form of the drill's tool edge. An investigation into the form of the tool edge with regard to low-cost, high-precision, and high-efficiency machining processes was performed. Suppression of the delamination at the exit surface of the drill by reducing the thrust force during drilling was considered. In first experiment, the CFRP had a thickness of 4 mm. A sintered carbide, straight shank drill tooling with a diameter of 6 mm was used in this experiment. Ten different types of straight shank drills with different point angles and coating treatments were tested. Additionally, this experiment evaluated the cutting force, cutting temperature, and CFRP delamination at the exit surface of the drill through drilling and processing of 100 holes. Moreover, second experiment evaluated the effects of honing the tool edge with regard to drilling and machinability of CFRP. The experiment used CFRP with a thickness of 8 mm and four types of sintered carbide drills. As a result, the delamination distance of the exit surface of the drill became smaller at point angles of 130° and 140°. No differences in the cutting force or the cutting temperature were observed because of difference in point angles. For the results of evaluation for the case without honing, the thrust force becomes 1/3 times less than that for the case with a honing drill. Additionally, for the case without honing, CFRP delamination was suppressed at the exit surface of the drill.