Hybrid tool servo diamond turning of multiscale optical surface based on spectral separation of tool path

Multiscale optical surface (MOS) that contains non-rotational symmetry micro-features and large sag height macro-features is promising in optics, due to their special optical advantages. Diamond turning with the slow tool servo (STS) or fast tool servo (FTS) is widely used for fabricating optical surfaces. However, due to the limited dynamic performance of STS and the small stroke of FTS, applying STS or FTS alone cannot efficiently fabricate MOS. Therefore, in this paper, a hybrid tool servo (HTS) diamond turning technique was presented to efficiently produce MOS. By integrating characters of the high dynamic performance of FTS and long stroke of STS, the new technique fulfills the strict requirements of manufacturing MOS. Methods for generating tool path in CAD software and separating the tool path into STS path and FTS path based on its spectral features were proposed. Besides, tool path evaluations were conducted to predict the profile errors with considering the dynamic performance of STS and FTS, based on the suitable machining parameters selected. A machining experiment of a typical MOS was carried out using the proposed technique. Results showed that the MOS was efficiently fabricated with no tool interference mark on the fabricated surface and a maximum profile error of about 2.8 μm.