Research Initiation: Ultra-Precision Machining of Glass Components

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This project is to advance the technology of high-precision grinding of glass, known as "ductile regime grinding", with the specific aim of eliminating surface fracture and subsurface damage. With this new technology, many materials that have previously been difficult to machine to accurate shapes because of their brittleness can now be machined to mirror finishes in a single grinding operation. This improved material-removal process is made possible by controlling the grinding infeed to rates below 100 nanometers per grinding wheel revolution. This process adapts the ductile-regime, and even the new technology described above cannot completely eliminate surface fracture during the grinding of glass. It is proposed that by introducing a diamond polishing slurry between the grinding wheel and the workpiece, high precision optical-quality glass components could be produced for the first time with a single machining operation. An additional benefit resulting from the introduction of a polishing slurry into the grinding zone is that it will permit ultra-precision grinding of large (greater than 1 meter) optical components, an application that has previously been considered to be impossible because of the rapid dulling of the diamond grinding wheel in the machining of glass. In this application, the combined grinding/polishing approach has considerable merit: by continually dressing the wheel, the loose abrasive solves the problem of grinding wheel dulling. At the same time, the precise control of tool position offered by grinding overcomes the inherent contour inaccuracies that are encountered in polishing operations.