A study of the performance of cutting polycrystalline Al 6061 T6 with single crystalline diamond micro-tools

A study was carried out to understand the mechanism of cutting polycrystalline Al 6061 T6 with single crystalline diamond (SCD) micro-tools using a 5-axis ultra-precision machine. The crystallographic structure, such as grain size and grain orientation, was found to play a significant role on the cutting performance. Variations in cutting force, chip formation and machined surface finish were observed as a result of changes in crystallographic structure. The hard and brittle micro-particles were found embedded in the metal matrix of Al 6061 T6. Cracks generated in the hard particles could be observed on the machined surface after the hard particles were brittle-mode cut by a micro-tool at a coarse cross-feed. These cracks also lead to surface imperfections such as voids or scratched lines on the machined surface. Cutting strategies of reduced cross-feed and/or applying ultrasonic vibration on the micro-tool tip were demonstrated to achieve a stable-state cutting performance with constant cutting force, an improved roughness of the machined surface finish and reduced burr size. High aspect ratio micro-pillar arrays with individual pillar size down to ∼1.1 × ∼1.3 × ∼5.3 (height) μm have been generated employing the cutting strategies.