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The generation of tool paths for ultra-precision machining is still a limiting factor in the manufacturing of parts with complex optical surfaces. In conventional machining as well as in complex five axes machining the application of CAD-and CAM-software for the generation of tool paths is state of the art. But these software solutions are not able to generate tool paths according to the high requirements of ultra-precision machining. This paper describes possible ways to generate tool paths for ultraprecision machining when the optical surface can be analytically described or when the surface data is derived from optical design software. Ultra-precision milling experiments with different tool paths have been carried out and the quality of the machined geometry has been evaluated concerning the achievable form accuracy.

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So far ultraprecision diamond machining of steel molds for optical applications is not possible because of excessive wear of the applied diamond tools. This article discusses a thermochemical approach for steel machining with single crystal diamond tools as well as the process of material modification. Ultraprecision raster milling experiments for the nitrided carbon steel C45 ͑AISI 1045͒ and the tempering steel 42CrMo4 ͑AISI 4140͒ are presented. In both materials a surface roughness of RaϽ 10 nm could be achieved. The observed flank wear of the cutting tools was VBϽ 2 m for all experiments after cutting work pieces with a diameter of 30 mm.

The mass production of glass or plastic components by replication techniques, like hot pressing or injection moulding, requires inserts made of temperature resistant and hard materials. Generating an optical surface finish in these materials is time consuming and difficult. By using thermo-chemically treated steels as mould materials diamond cutting processes generating high form accuracies and low surface roughness can be applied without significant tool wear.