Review of single-point diamond turning process on IR Optical materials

Ultra-high precision machining is the most convenient manufacturing method for fabricating      various optical components from diverse materials. Desired surface finish of optical components along with form accuracy can be achieved with the help of single-point diamond turning (SPDT) process. SPDT is a unique process that employs monocrystal or single crystal diamond tool for the development of diffractive and aspherical surfaces. Nanometric edge sharpness and wear resistance are the attractive features of the diamond tool which is utilized in SPDT process for achieving sub-nanometer surface finish on the metal mirrors. Night vision, thermal imaging, infrared imaging systems, and astronomical applications are few examples of optical devices. The field of infrared (IR) optics is one among the fastest growing branches of traditional optics. Infrared (IR) applications in optics requires a good surface integrity and nanometric roughness deprived of microfractures, scratches and microcracks. Silicon (Si) and germanium (Ge) both are the elemental materials in IR optics. This paper aims at providing an overview of ultra-precision SPDT process for attaining sub-nanometer surface finish on the IR materials. Subsequently, the factors that influence the generation of surfaces are presented and discussed in detail through some significant work in this domain. After an extensive literature review on different aspects of precision machining using single point diamond turning (SPDT) process such as analytical modeling, experimental and simulation studies on various process parameters including effect of tool geometry and crystal orientation on the output responses, it was found that very scant literature is available on FE model to simulate the impact of input machining parameters on the distribution of the cutting temperature and thermo-mechanical deformation of the diamond tool while machining of IR material and further to understand the effect of complex interaction of input parameters on output response in terms of nanometric surface roughness with minimum subsurface damage and by minimizing the tool wear.