Automated Drilling of Fabric Woven CFRP and Aluminum Laminates with PCD Cutters Using Drilling Robot

CFRP has been widely used in aerospace industries because of its high strength-to-weight ratio. However, drilling CFRP laminates is difficult due to the highly abrasive nature of the carbon fibers and low thermal conductivity of CFRP. Therefore for the manufacturers it is a challenge to drill CFRP materials without causing any delamination within the high quality requirements while also considering the costs of the process. This paper will discuss the process of drilling CFRP-Al stack ups within tight tolerances using a seven axis drilling robot. All components required for drilling are integrated in the drill end-effector. The pressure foot is extended in order to clamp the work piece, and then holes are drilled. The drilling process has four steps: moving to the fast approach level, controlled drill feed, countersink depth reach and drill retract. The cutter diameter range chosen for this paper is Ø 4.0 mm and Ø 7.9 mm. We will mainly explain our observations and experience to achieve the tight tolerances and surface finish.