Measurable properties of Al2O3 ceramic injection molding raw materials

Abstract

Powder injection molding (PIM), which encompasses metal injection molding (MIM) and ceramic injection molding (CIM), is a process which enables large scale production of complex-shaped components for use in a diverse range of industries. Ceramic injection molding (CIM) is a technology for manufacturing complex, precision, netshape components from ceramic powder. In the illuminant industry, for producing arc tube parts for high intensity discharge lamps the applied method is the ceramic injection molding. The ceramic arc tube parts are made of high purity alumina powder. By producing ceramic parts, one of the most critical steps is to optimize the injection molding process, to determine and control the influential machine parameters, which have an effect on the quality of the end product. Nevertheless, the properties of injection molding raw material is needed to be known before any optimization of the injection molding process, because later the molding process is optimized for this material, to decrease the amount of cracked ceramics. For producing ceramic arc tube parts (plugs), there are two different major components used for producing injection molding raw material (feedstock): high purity alumina powder as the main component, and an organic paraffin wax as a binder material. It is expressly important to know the physical and dimensional properties of the alumina powder, since mainly these have affect on the homogeneity and viscosity of feedstock, and therefore on the quality of the end product. In the present research, both the main components and the moldable raw material were investigated by visual, physical, chemical and thermal methods. It was found – most importantly – that the viscosity of the raw material linearly decreases with the increasing grinding time of the alumina powder. Applied analytical methods in terms of laser granulometry, tap density analysis, differential thermo-analysis and rheology analysis were used.