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Large mirrors are required for a wide variety of applications. Two key constraints are mirror stability and mirror mass. Low expansion glass ceramics remain a useful material because of its excellent thermal stability, relative ease of processing and lower cost compared to alternatives. However there is room for the improvement of the manufacturing techniques over the traditional methods of milling and etching, which are high risk, expensive and time consuming. A solid blank is milled out using high speed diamond tooling to leave fragile webs of supporting material. The final process steps are the highest risk, when it is possible for catastrophic flaws to appear. We present a novel method of producing a monolithic structure from component pieces that provide a lower risk, lower cost method of producing stable and light-weighted mirrors. Individual smaller components are machined and then bonded together. The bonding process results in near substrate strength components without compromising the very low thermal expansion of the glass ceramic. It also allows the creation of novel designs with hollow cavities embedded within the structure. Prior to commencing the fabrication the mechanical design was modelled to predict the stability of candidate designs. Tests were carried out on witness pieces to prove the relative strength of the bonds. Prototypes were then fabricated and tested for thermal stability.
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