Modeling and optimization of dynamic performances of large-scale lead screws whirl milling with multi-point variable constraints

The complex nonlinear dynamic responses of the whirl milling system, caused by discontinuous cutting forces, could considerably affect the machining quality of large-scale lead screws (LLS). Fixtures including floating supports and holding devices are frequently utilized to improve the dynamic performance of the system, however leading to the Multiple-Point Variable Constraints (MPVC) of LLS workpiece during machining. It makes the dynamic performances of whirl milling complicated and hard to predict. In this paper, the dynamic model of whirl milling process is established considering MPVC induced by floating supports and holding devices, and the dynamic performances of large-scale lead screws are effectively calculated based on the logical assumption of boundary conditions of LLS workpiece and accurate representation of the three-dimensional cutting forces. Experiments of whirl milling for the eight-meter LLS workpiece are performed to validate the proposed dynamic model, and the results calculated from the proposed model are in good agreement with the experimental results. Further, the effects of floating supports are investigated to optimize the dynamic performances of whirl milling. The results show that the proposed dynamic model is feasible and effective for the modelling and optimization of dynamic performance of whirl milling processes.