Comparative study of robotic common countersinking and robotic longitudinal-torsional composite ultrasonic countersinking experiments

Abstract The robots with low stiffness are prone to chatter during countersinking, which inevitably reduces the accuracy of the countersink depth. In this paper, a method for decreasing the chatter of the robotic system is proposed by combining the robotic countersinking and longitudinal-torsional composite ultrasonic machining technology. Through the comparative study of robotic common countersinking (RCC) and robotic longitudinal-torsional composite ultrasonic countersinking (RCUC-LT) experiments, the feasibility and effectiveness of introducing ultrasonic vibration to improve the quality of robotic countersinking CFRP/Al stack have been proven from the three aspects: cutting force, hole wall quality and countersinking depth. The experimental results show that the cutting force of RCUC-LT has decreased by 35.69% than that of RCC. The hole wall quality of both CFRP and Al has been improved. Finally, for RCUC-LT, the values of countersinking depth are controlled between 1.45mm and 1.55mm, while most of the values of RCC exceed this range. Longitudinal-torsional composite ultrasonic machining technology is an effective way to improve the quality of robotic countersinking.