SINGLE-POINT DIAMOND TURNING PROCESS FOR ULTRA-PRECISION OPTICAL SURFACE GENERATION

Ultra-precision manufacturing is the recent realm in advanced manufacturing, subsequent to the precision manufacturing technologies, for generating optical components with nanometric surface characteristics. Single-point diamond turning (SPDT) is the leading technology in the manufacturing of optical components with optical surface roughness down to one nanometer, which ensures extremely smooth optical surfaces. SPDT technology has a wide range of applications in different industry sectors, including military, defense, aerospace, biomedical, electronics, computer, and entertainment. In SPDT, a mono-crystalline diamond is used as the cutting tool for cutting the workpiece surface. Cutting-edge technologies and state-of-the-art machining solutions are used in the development of SPDT machines, to achieve the best possible outcome in terms of cutting accuracy and the quality of optical surface generation. Yet, during the optical surface generation process, many factors can negatively affect the optical surface generation mechanisms and reduce the quality of the machined surface. Different types of tool wear, as well as high cutting temperature, are some of the important machining factors that negatively influence the optical surface generation mechanisms and reduce the quality of the optical surface finish.

Experimental studies, as well as modeling and simulations, have been conducted to discover the factors that influence the diamond turning process and their direct and indirect effects on the quality of the optical surface finish. The main factors that influence the optical surface generation and increase the optical surface roughness are listed as follows: environmental parameters, cutting parameters, workpiece material properties, machine tool parameters, diamond tool geometry, tool wear, passive vibration, chip formation, shear angle, material swelling, and recovery. Different studies have been conducted to evaluate the impacts of mentioned influencing factors on the optical surface generation mechanisms, resolve the existing limitations of the SPDT machining process, optimise the SPDT condition, and reduce the effects of the harmful factors during the optical surface generation process.

Better results, in terms of the quality of the turned workpiece, can be obtained by setting the optimised machining parameters and tuning the machining factors. However, there are still limitations in the SPDT process, especially when a diamond tool is cutting hard-to-cut and brittle materials including titanium alloys and silicon. High tool wear, low diamond tool life, and high surface roughness are some of the factors that are induced during the turning of materials that have low machinability with the SPDT technology. There are still gaps between the developed SPDT platforms and an ideal SPDT platform for generating the best possible optical surfaces with minimum optical surface roughness