Study on cutting force and surface topography of screw rotor ball end milling process based on normal cutting depth iteration algorithm

Because of the high manufacturing precision and efficiency, the segmented grinding and ball-end milling method is often used in the finish machining process of the variable screw rotor instead of form grinding. To study the process of the rotor ball-end milling and improve the precision of the machining process simulation, the accurate tool-workpiece surface contacting model and cutting force model must be established first. In this paper, the normal cutting depth iteration algorithm was proposed to study the time-varying mapping relationship between the cutting edge trajectory and the workpiece. And the normal cutting depth was used instead of the cut-in angle, cut-out angle, and undeformed chip thickness to establish the cutting force model. The influence of the transitional surface topography on the undeformed chip thickness in the cut-in and cut-out process was calculated by this method. Then, the cutting force of the screw rotor cut-in process could be simulated precisely in the finish cutting process. In this paper, the normal manufacturing error of the rotor surface and cutting force of the screw rotor were measured, and the results showed that the experimental data and the simulation data were within 15%, which proved that the method could accurately simulate the cutting force and surface topography in the ball-end milling process.