Wu, H-Y; (2016) Robotic processes to accelerate large optic fabrication. Doctoral thesis , UCL (University College London).

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Abstract

The manufacture of metre-scale optics for the next generation of extremely large telescopes (and many other applications) poses a number of unique challenges. For the primary mirror of the European Extremely Large Telescope, each of its 1.45 m segments will need to be completed with nanometre scale accuracy. This demands an unprecedented combination of hybrid fabricating technology to process nearly 1000 segments before the year 2024. One important aspect in improving the current state-of-the-art manufacturing developments is adding an efficient smoothing process that can achieve a faster, and less expensive, manufacturing process-chain. The current process to finish a prototype segment using CNC grinding and CNC polishing takes approximately 1-2 months, and a significant contributing factor in this is the excessive processing times needed to correct the local grinding marks. In this study, therefore, grolishing, an intermediate process between grinding and polishing, is adopted to smooth the part and reduce the overall manufacturing time. This PhD work serves to advance the development of effective robotic grolishing processes (RGP) by the following achievements: (1) to propose the specification and achieve the requirements; (2) to design tools and establish a mechanism for grolishing; (3) to investigate and propose experimental methods to reduce process times while still achieving high performance, reliability and quality surfaces; (4) to establish the RGP and demonstrate that this process can smooth the errors from grinding and provide superior surfaces for polishing to speed up the current process; (5) to develop prototype metrology systems and algorithms to measure grolished surfaces; and, (6) to investigate an innovative proposed method to control mid-spatial frequencies on complex surfaces by using rotating rigid tools. These novel achievements describe the newest fabrication technology, and anticipate the evolution of the process-chain for future high-quality imaging systems for use in astronomy, space-research and laser physics.

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