This paper presents an analytical approach to investigating the chip formation process in micro-milling aluminum 6082-T6 particularly by using natural diamond and tungsten carbide tools. Through well-designed micro-milling experiments, a comparative study is conducted by utilizing a natural diamond tool with the perfectly sharpened cutting edge and a tungsten carbide tool with the rounded cutting edge respectively. Cutting forces are recorded and analyzed as one of main process indicators. The chip morphology and micro milling processes are analyzed in correlation with cutting force variations in the processes. The size effect, minimum chip thickness and their integral effect are quantitatively assessed against the chip formation process. Research results show that the chips formed during the consecutive revolutions are affected jointly by the cutting tool/workpiece material pair and the cutting edge radius in using tungsten carbide tools; whereas the chips formed by using diamond tools are intact and separate. Furthermore, the cutting force and thrust force are of the same order due to the cutting edge radius cannot be ignored. For using a natural diamond tool with the sharp cutting edge, the resultant cutting force is usually two times higher than the thrust force.

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Micro-optical components made from polymethyl methacrylate are increasingly in demand. This article presents an experimental investigation into diamond micro-milling of polymethyl methacrylate components with nanometric surface roughness and its application perspectives. The experimental micro-milling trials with a chemical vapour deposition diamond ball endmill are conducted on a self-developed ultra-precision micro-milling machine (UltraMill) featuring high precision and high dynamic performance. Surface roughness of micro-milled slots using different micro-milling strategies is measured with white light interferometer. Results show that when feed and cutting orientations are perpendicular, smaller surface roughness can be obtained. Micro-milling is carried out on 2 × 2 mm2 areas by applying different micro-milling strategies and process parameters. The results demonstrate that the micro-milling strategy which can generate good surface roughness in slot micro-milling cannot produce expected surface roughness on such a large area (2 × 2 mm2), and machining dynamics plays an important role. By applying two-way joint micro-milling strategy and adjusting process parameters, an optical surface is obtained with roughness of 8.717 nm.

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Drag reduction in wall-bounded flows can be achieved by the passive flow control technique through the application of bio-inspired ribleted surfaces. In this paper, innovative design and manufacturing of serrate-semi-circular ribleted surfaces are presented with application to friction and drag reduction on engineering surfaces. Firstly, the design of the ribleted surfaces is described particularly focusing on the serrate-semi-circular shaped structures. Secondly, machining of ribleted surfaces by fly-cutting is investigated, covering the utilization of bespoke CVD diamond tools on a micro-milling machine and the corresponding micro fly-cutting processes. Metrology measurement results show good agreement achieved between the designed and machined surface features. Experiment conducted in wind tunnel shows the machined surface can produce 7% in drag reduction. Compared with conventional micro milling, the micro fly-cutting technique resulted from this research illustrates the unique advantage and industrial significance, particularly for manufacturing microstructured surfaces in an industrial scale.