Effect of Laser Preheating the Workpiece on Micro end Milling of Metals

Micro end milling is a fast and direct method of creating net-shaped functional microparts, micromolds, and prototypes. However, the small flexural stiffness, strength, and hardness of the tool limit the efficiency of machining. It is not expected that a new material with increased hardness and yield strength will be developed in the near future that significantly improves the durability for tools manufactured with diameters in the tens to hundreds of microns. To enable a significant increase in performance and productivity requires higher spindle speeds and increased chiploads. However, an increase in chipload is inhibited by the small flexural stiffness and strength of the tools: a direct result of the tool diameter. Laser-assisted micro end milling has the potential to increase the chipload and productivity by locally reducing the workpiece material’s yield strength at the cutting location. This study examines the effect of laser preheating on micro end milling of 6061-T6 aluminum and 1018 steel. Two-flute, 300μmdia, carbide end mills are used to cut 100μm deep slots at a spindle speed of 40,000rpm. The laser power and chipload are varied to show their effect on cutting forces, specific cutting energy, burr formation, surface finish, and temperature. The results are compared to the average material removal temperature given by predictions made from a heat transfer model of the workpiece undergoing laser preheating. Results indicate that chipload and productivity can be significantly increased during dry machining of 6061-T6 aluminum and 1018 steel by localized preheating of the workpiece.