Effects of Gripping Force of Hydraulic Three-Finger Power Chuck on Modal Stiffness and Tool Life

Abstract

In this study, tool wear in cutting of titanium alloy (Ti-6Al-4V) was investigated when the contact condition of a lathe chuck and workpiece was changed by gripping force of the soft jaw. A workpiece with 90 mm in diameter and 180 mm in length was chucked by cantilever support. Cutting speed was 150 m/min, depth of cut was 0.2 mm, and feed rate was 0.1 mm/rev. Stress distribution of the contact surface of the soft jaws, and static and dynamic stiffness of the main spindle system were also measured to explore the main cause of tool wear variation. The static stiffness of the spindle system increases with increasing into gripping force because by resistivity against bending at the chucking position increases due to the increment of conformity in axial direction between the jaws and workpiece. Accordingly, the modal frequency of the main spindle system increases. Furthermore, the tool wear variation was influenced with this modal frequency of modal vibration.