Drilling of CFRP with an Electrodeposited Diamond Core Drill – Effects of Air Assistance and Tool Shape –

This research was conducted to investigate the characteristics of electrodeposited diamond core drills when used to cut CFRP.An eccentric core drill was usedto improve cutting characteristics. First of all, the cutting characteristics of a normal core drill were investigated at a few different feed rates and compared with those of a diamond coated twist drill. The effect of air assistance on chip evacuation were also investigated. The cutting forces, surface roughness profile of the hole, and tool appearance were used for evaluation. At the same feed rate, more cutting force was necessary for the normal core drill than for the twist drill. When air was blown in, the cutting forces required by the core drill decreased drastically, but delamination was evident. When air was drawn out, the cutting forces of the normal core drill were almost the same as when there was no air assistance. On the other hand, when an eccentric core drill was used, the cutting force required was lower when air was drawn out than when it was blown in. Additionally, the surface quality of the hole when air was drawn out was greater than when it was blown in. When the eccentric core drill with slits was used while air was drawn out, the cutting forces, surface quality of the hole, and tool appearance were the same as when an eccentric core drill without slits was used. However, there was little core jamming. Therefore, the eccentric core drill with slits had the longest tool life.