Study on the mechanism of the Surface Defect of the Ceramic Injection molded (CIM) Insulator

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Title:	Study on the mechanism of the Surface Defect of the Ceramic Injection molded (CIM) Insulator
Authors:	Feng-Jen Hsu, Chao-Tsai (CT) Huang*, Richard Lee, and Denni Liao
Keywords:	ceramic injection molding, high voltage insulator, surface defects, volume shrinkage
Date:	2018-05-23
Issue Date:	2018-10-04 12:11:34 (UTC+8)
Abstract:	Insulators have been applied in many fields, such as in industry, medical, or military very often. Especially, in high voltage environments, insulator plays a very important role. In general, inorganic or plastic materials are used for the low voltage insulator, but the ceramic material is applied for fabricating the high voltage insulator. The most common method to fabricate ceramic insulator is ceramic powder injection molding (CIM). Based on this method, the good quality for high voltage and mass production can be obtained. In general, the ceramic powder and some plastic are mixed, and then the mixed material is delivered into injection molding process. The major procedures can be divided as the mixing of the ceramic powder and plastics to prepare the feedstock, injection molding to make the green parts, thermal debinding, sintering, and post processing [1-3]. As the CIM process is performed, some surface defects will be generated during the injection molding step. These surface defects will become very serious problem after thermal debinding and sintering. Recently, some researchers suggested that those surface defects could be related to the non-symmetrical volume shrinkage during the injection molding period in the formation of green parts. Thomas and Evans [4] have tried to applied alumina to make ceramic green part. They found out some tiny crack in green parts where would become a big crack. They proposed that the final crack is strongly related to the molding process. Jansen et al [5] tried to understand how the shrinkage behavior happened in injection molding. They had systematically considered various operation conditions including injection speed, package pressure, melt temperature, and mold temperature for seven polymer materials. They found out the major factors to influence the volume shrinkage of injected parts are melt temperature and packing pressure. Moreover, German [6] suggested that the improper high melt temperature will enlarge the defects. The non-uniform volume shrinkage will cause the void and crack defects for the final products. Although many researchers proposed that the surface crack defect is related to green parts during the injection period, how the quantitative relationship is not fully understood yet. Hence, in this paper we will try to build this relationship between the surface defects of final ceramic product and the physical property of the green parts during the injection molding.
Relation:	PPS-34 Proceeding
Appears in Collections:	[Graduate Institute & Department of Chemical and Materials Engineering] Proceeding

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