Evaluating surface roughness, tool life, and machining force when milling free-form shapes on hardened AISI D6 steel

Abstract

Today, the AISI D6 tool steel has been employed in the manufacture of dies and molds that require high mechanical properties. Such hard material is not trivial to machining. Milling free-form geometries of D6 is a challenge usually faced at die and mold industries. Therefore, the current paper presents an investigation of free-form milling of hard material AISI D6 tool steel using a ball-end cemented carbide cutting tool. The influence of the toolpath direction (descendant and ascendant) and tool-workpiece surface contact were examined, and the machining forces, surface roughness, tool wear, and tool life were evaluated. The experiments were performed in two kinds of workpieces: in the first one, the milled surface was a cylindrical and in the second, the surface was inclined planes (with three different inclinations). The results indicate that the most influential factor for tool life was tool vibration. The higher the vibration, the shorter the tool life. Further, unlike milling of ordinary materials for molds and dies, the engagement of the center of the tool tip during cutting is advantageous for the machining process of hard materials because it improves cutting stability, thus reducing surface roughness and increasing tool life.