An experimental investigation on micro-milling of polymethyl methacrylate components with nanometric surface roughness

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 x 2 mm(2) 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 x 2 mm(2)), 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.