Feed Rate Variation Strategy for Semi-Conical Shell Workpiece in Ball Head End Milling Process

Abstract

The semi-conical shell workpiece is a special kind of thin-wall part that is commonly used in aerospace and mold industries. Due to the special stiffness distribution and weak rigidity for the area with a large radius, the machining quality of the semi-conical shell is sensitive to both cutting force and vibration. Conventionally, constant conservative machining parameters are chosen to ensure the workpiece deformation and surface quality, which will reduce the machining efficiency. Based on the cutting force and vibration response simulation of the whole milling process. A feed rate variation strategy is proposed for the ball head end milling process of the semi-conical shell workpiece. The cutting force, dynamic performance and stability prediction are obtained considering the shape and boundary conditions of the workpiece and the contour tool path of the milling process. Variable feed rate is used in the milling simulation to find the harmony between machining quality and efficiency. User-defined vibration amplitude and another user-defined cutting force threshold are used to find the optimal feed rate for each simulation segment. Both continuous and discrete feed rate variation strategies are proposed, and the improved discrete feed rate variation is applied in the milling experiment. About 25% of the consumed time is saved with almost the same machining quality by the experimental results.