Drilling of Carbon Fiber-Reinforced Plastic with Double-Angle Drill Using Industrial Robots

Improving the versatility of robots and implementing offline teaching are essential for enhancing manufacturing productivity. Robotic machining has gained traction as a key industrial application, as robots can process workpieces larger than their own structures. This capability renders them highly effective for machining large-scale components, such as those used in aircraft manufacturing. In the machining of large workpieces, the post-processing of carbon fiber-reinforced plastic (CFRP)—such as drilling for component assembly—is typically required. However, drilling CFRP presents the challenge of delamination. Although the application of a double-angle drill (DAD) can suppress delamination at the hole exit, it does not suppress delamination at the hole entrance. To address this challenge, the robot posture is optimized to increase compliance in the thrust direction, thereby suppressing the delamination at the hole entrance. To validate this approach, a robotic machining system is used, equipped with a spindle motor and DAD on the end effector of the large industrial robot. The results demonstrate that the thrust force at the entrance is greater than that at the exit, thereby exacerbating delamination. However, by optimizing the robot posture to increase compliance, delamination is effectively suppressed, and the hole diameter error is reduced. These findings indicate that drilling CFRP with an optimized robot posture can effectively suppress delamination and improve machining accuracy.