An Analytical Approach for Machining Thin-walled Workpieces

An analytical approach is developed to predict the dynamic chip thickness variation in ending milling of thin-walled workpieces. The proposed model considers the mechanism of calculating the stiffness of removed material by the end- mill from the overall stiffness of the workpiece to work out the changing stiffness of the workpiece which in turn is used to determine the displacement occurring. The displacement of the workpiece influences the radial depth of cut and thus yields a dynamic variation. The generalized model of the volume of removed material is computed by considering the discrete axial depth of cut, the radial depth of cut and the circumferential section of the tool radius contact for each tool step taken. The features of this model cater for the helical tool geometry used. The stiffness of removed material is updated by subtraction from the overall stiffness of workpiece. The overall stiffness of the wall is updated by considering the removed material at each time step. The feedback of the displacement amplitude is linked with a cutting forces model to address the influence of the dynamic displacement of the workpiece from the acting chip load. The cutting forces is modeled based on the Oxley variable flow stress machining theory. The predictive capabilities of the proposed model are verified with the experimental results. The comparison of the results is encouraging and reasonable correlation is achieved.