Major lighting companies have released the volume production of Ceramic Metal Halide (CMH) lamps and its market growth rate is maintained by around 30% every year. In 1990s Philips announced the first design of Mo-Nb composite electrode system which uses translucent ceramic discharge vessel, a cylindrical body with two capillaries.'1' That cylindrical vessel has corners at the both end and they make cool spots.12' If a completely spherical or oval vessel is available, a lamp performance, such as color rendering, efficacy, anti-corrosion and mechanical strength can be improved. '3) Some patents and papers reported manufacturing method of such spherical vessel.'4'"'1' They attribute unique design with accurate dimension tolerance to only small quantity of samples, however it is very few such unique vessel design is released to volume production with reasonable manufacturing cost. On the other hand translucent ceramic vessels are widely used for High Pressure Sodium (HPS) lamp application and its manufacturing technology has been matured, which achieved enough stable manufacturing cost. NGK is one of the most experienced HPS ceramic vessel manufacturers in the world. We developed the volume production process of seamless CMH discharge vessel in high cost performance, utilizing HPS ceramic vessel manufacturing technology. The research was focused to forming technology of seamless spherical shape.
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