Drilling of CFRP/Ti-6Al-4V with Step Drills

Abstract

In drilling of Carbon Fiber Reinforced Plastics (CFRP)/titanium alloy stacks, the chip flow should be controlled to finish the hole without any damages on the surface of the CFRP layer. A step drill is applied to drilling of Ti-6Al-4V stacked CFRP for improvement of the surface finish and reduction in the production time. The cutting force and the chip flow are simulated by the energy approach, in which the chip flow angle is determined to minimize the cutting energy. The diameter of the pre-machined hole and the wedge angle of the step edge are discussed with the chip flow angle on the end of the lips, which finish the surface in the hole, and the chip flow velocities. The geometry of the step drill is designed to flow the chip of Ti-6Al-4V upward with the cutting simulation. The designed step drill is verified to finish scratch-free surfaces inside of the holes.