Improvement of Surface Flatness in Face Milling by Varying the Tool Cutting Depth and Feed Rate

This paper explores two approaches to improve the flatness of face milled surfaces by modifying the tool cutting depth and feed rate based on the 3D holographic laser measurement. The tool cutting depth compensation method generates a cutting path which is the mirror image of the measured error profile to reduce the flatness errors. Issues of back-cutting and the interference due to cutter size limit the range of applicability of this approach. The feed rate is varied to match the axial force on the cutter with the local compliance of the workpiece to further improve the surface flatness. Using a flat plate workpiece and 50.8 mm diameter face milling cutter, the surface flatness can be reduced from around 15 μm without compensation to lower than 10 μm by varying tool cutting depth. Modification of feed rate further reduces the flatness errors from 10 μm to 6 μm. Automatic tool path compensation based on holographic feedback is also discussed.