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2008
Conference Paper
Titel
Precision grinding with CVD diamond coated grinding tools
Abstract
Todays diamond grinding wheels have restrictions for very small grit sizes, that are needed for achieving the smoothest surface finish, e.g. for fine optics applications (photo lenses, microscope lenses). The aim in lens fabrication is to reduce the polishing effort, since polishing improves the surface finish but can reduce the form accuracy. The reason for the limited surface finish is the bonding technique used for todays diamond grinding wheels. Very small diamond grit sizes of D 3 to D 15 are difficult to bond onto the tool body in terms of grit protrusion, layer thickness uniformity and from accuracy. Furthermore, the cutting edges would improve the abrasive process. CVD (chemical vapor deposition) diamond layers are an alternative to bonded diamond wheels. The microcrystalline diamond layer is formed out of many small crystalline tips, having atomistically sharp edges. The crystalline width and height can be set to very small dimensions, easily to 5 micron and smaller. Very precise thickness uniformities can be achieved. Grinding wheels of 80 mm diameter have been coated with CVD diamond grinding layers with crystallite widths of 8 microns. Tests have been performed on an topic grinding machine for the grinding of glass lenses. A surface roughness Ra of 0.17 micron was achieved.