Tool life and surface roughness in the milling of curved hardened-steel surfaces

Abstract

The manufacturing of molds and dies requires that complex hardened-steel surfaces be milled. The deep cavities in these parts are generally cut using high-speed machining technologies and long, slender tools. Consequently, the milling cutter has a tendency to vibrate, potentially damaging the surface of the workpiece and causing the cutting tool to chip or break. This study investigates tool life, cutting forces, and surface roughness in ball-end milling of a curved, convex surface of AISI D6 tool steel with a hardness of 62 HRC. The main goal was to find cutting conditions that provide good surface quality with long tool life. Two cutting strategies (upward and downward) with three lead angles (−16°, 0°, and 16°) were tested. Analysis of variance was used to understand the results better. Adhesion followed by chipping of the cutting edge was the main wear mechanism found. The results show a close relationship between radial components of the machining forces and surface roughness and tool life. The cutting conditions that provided the lowest radial force also generated the best surface finish and the longest tool life (an upward strategy with a lead angle of 0°).