The machinability and anisotropy of bio-CoCrMo manufactured by directed energy deposition in ultrasonic vibration assisted drilling

Holes are an essential component in achieving the desired function of implants. As the prevalent application of additive manufacturing in the field of implants, the hole-forming quality of additively manufactured parts using conventional machining has become a limitation. In this study, the material anisotropy is first characterized and the machining response of the materials anisotropy during ultrasonic drilling is investigated. To reveal the machining advantages of ultrasonic drilling for additively manufactured parts, a hybrid cutting simulation is employed to simulate the behavior how the ultrasonic vibration removes impurity particles. A chip breakage evaluation model that takes the ultrasonic frequency variation into account is also developed to explain the improvement mechanism on hole surface uniformity. The subsequent drilling experiments demonstrate that ultrasonic drilling can improve the quality of hole machining for additively manufactured parts. The research has potential to advance the development of additively manufactured implants.