Analysis of Cutting Forces and Mechanism of Chip Formation in Ball End Milling of Inclined Surface (2nd Report)

Abstract

In order to predict cutting forces and chip formation in milling with a ball end mill for various tool paths, inclination of the workpiece surface and of the tool axis, a cutting model proposed in previous paper is extended to the milling process in which both cutting edges of the sphere and cylindrical portions engage with the workpiece. In the cutting model, elemental chip at any point on the cutting edge is described by simple shear plane oblique cutting model, and the condition of side-curl of the chip is considered. In this paper, cutting edge configurations, inclination and normal rake angles at the sphere and cylindrical portions are discussed. Geometric quantities such as contact region between the cutting edge and the workpiece surface, and undeformed chip thickness along the cutting edge in milling for the tool moving upward or downward on the inclined surface are analyzed, and variation of these geometric quantities with tool rotational angle are also discussed. Three components of the cutting force and chip formation such as chip flow angle, radius of side-curl of the chip and chip form are predicted by using developed cutting model and energy method. The preliminary examination shows that there is the large difference in cutting forces and the chip formation for the tool moving upward or downward on the inclined surface.