Material identification method for helical milling of CFRP/Ti stacks based on torque-speed model

Because of the excellent material properties of carbon fiber-reinforced plastic composites (CFRP) and titanium alloy (Ti), CFRP/Ti stacks are extensively used in the aerospace industry. As the foundation for connecting the above two materials, there is increased requirement and workload for CFRP/Ti stack integrated hole-making process in aerospace assembly. Due to the limitations of the huge difference in machining properties between these two materials, the applicable machining parameters of each layer material are different. In this paper, a material identification method for helical milling of CFRP/Ti stacks based on the torque-speed model is proposed to solve this problem. The torque prediction model is proposed for helical milling of CFRP and Ti; then the function of torque with respect to spindle speed is resolved. Meanwhile, the torque-speed model of pneumatic spindle is presented based on the multifunctional portable helical milling equipment independently developed. The predicted speed of equipment when processing different materials is solved by correlating the above models, thereby establishing the corresponding relationship between the spindle speed and material for identification. Validation experiments were conducted and the results show that the torque prediction errors for CFRP and Ti are less than 7.5% and 6.9%, respectively, which indicate that the torque prediction model has good accuracy. Furthermore, the spindle speed prediction errors for the two materials are within 7.1% and 6.1%, respectively. The results show excellent consistency, which demonstrate that the proposed method can accurately identify the material types and provide a theoretical basis for subsequent processing.