Modeling and Cutting Path Optimization of Shallow Shell Considering its Varying Dynamics During Machining

Abstract

During the milling process of shell structures, such as blades and engine casing, the change of thickness varies the dynamics of the workpiece considerably, which may induce unstable cutting conditions and thus influences the quality of the machined surface. In this paper, common shell structures are firstly simplified as doubly curved shallow shells to notably minimize the computation amounts, and then an analytical model was presented to predict the dynamic changes in the material removal process. The Ritz method and the thin shallow shell theory are combined to solve the dynamic characteristics of the shallow shell structures.Furthermore, based on the simulation results of the above analytical model and the stability lobes theory, the workpiece is divided into several subregions according to the variation of dynamics stiffness. In each subregion, the dynamic characteristics are assumed to be constant to simplify the analysis. Afterwards, trial cuts are performed respectively in each subregion to select the best cutting parameters. The optimized tool paths are generated according to the trial cuts which will guarantee a stable cutting operation during the entire machining process with high efficiency and good surface quality. Finally, experiments are performed to verify the proposed method.