Abstract: Polycrystalline alumina (PCA) in high pressure discharge lamps can have different shapes, such as spherical with two small openings or cylindrical, plugged with larger openings for electrodes. Cylindrical tubes can be vertically extruded, but due to low material efficiencies, injection molding was investigated. Electrical injection molders have precision to modify the velocity and easily mold arc tubes as well as complex shapes. Besides the molding equipment, a major modification is the debinding process, which uses a wicking agent to remove a percentage of binder. Due to one end of the tube being open, the wicking agent can coat all surfaces compared to the outer surface of a hollow body. Testing the effect of the direction of tube opening through debind resulted in varying sintered dimensions. Results show that the more intimate contact of the wicking agent produced increased shrinkage in the sintered state.
Author: Jordan Otminski
Keywords: Injection Molding, High Purity Alumina, Translucent PCA