Nonlinear dynamics of the milling head drive mechanism in five-axis CNC machine tools

As an essential assembly in five-axis CNC machine tools, the milling head with high-power and high-torque is used in processing the titanium, superalloy, and other high hardness materials. However, nonlinear friction, structural flexibility, and other factors affect the positioning precision and dynamic characteristics of the milling head seriously. To achieve perfect performance, dynamics investigation is necessary in the initial design. Firstly, considering the nonlinear friction and structural flexibility, a nonlinear dynamics model is established. Secondly, based on least squares method and genetic algorithm, static and dynamic parameters are identified for the LuGre friction model, and the axial elastic coefficients are calculated by the pressure tests. Finally, the dynamics model is solved by Newton-Simpson algorithm and Newmark-beta algorithm. Additionally, influences of related parameters on dynamics performance of the milling head drive mechanism are investigated. The theoretical model and experimental results derived in this paper provide basis for the optimal design and error compensation control of the milling head drive system.