Ultra-precision diamond turning of optical silicon—a review

In traditional approach of silicon optical lens production, grinding, lapping, and polishing are employed. Success of these steps depends on the quality of the preceding ones; therefore, use of precision grinding is becoming an unwise decision during manufacturing of optical lenses with complicated surfaces. Owing to this, an alternate manufacturing approach for producing silicon optical component was sought. Ultra-precision diamond turning using a single-crystal diamond tool with a high negative rake angle while maintaining a cutting regime in the ductile mode is now widely used as the alternate approach. However, depending on view point, machinability in ultra-precision machining may be in terms of tool wear rate, hardness, chip shape, surface roughness, and other benchmarks. Therefore, determining proper machining conditions, such as tool geometry and processing parameters, is crucial in achieving the required surface finish and optical form accuracy. In determining the optimal process parameter settings in silicon diamond turning, numerous process trials are generally required to evaluate the most favorable machining variables and their interactions. To improve the machinability of silicon, this review article presents an overview of the previous research on the effects of both machining parameters and tool geometry to optical silicon machinability. This is aimed at facilitating adequate understanding of the deformation, fracture, surface quality, and microstructural changes of both silicon and diamond to ease attainable product quality, utility, and quality cost.