Skin Layer Formation in Plate Model for Coupled Analysis of Injection Molding Process of Bonded Magnets

Abstract

The bonded magnet, which is formed by mixing magnet materials such as neodymium-based and ferrite-based materials with resin, has the characteristic of being able to be formed into small and complex shapes due to the resin being the binding material. It is used in small motors embedded in hard disk drives and motors for home appliances. The major methods for forming bonded magnets are compression molding and injection molding. In this study, injection molding is selected, which can easily apply to complex shape compared to compression molding. However, injection molding has the disadvantage of variability in density and magnetic properties of the molded products. This is due to the difficulty in observing the material flow, as the molding process progresses inside the mold and multiple processes occur simultaneously such as injection, compression, magnetization, and curing. Therefore, determining the optimal molding parameters for injection molding of bonded magnets requires numerous experimental trials. Based on the above, it is believed that predicting the behavior of resin inside the mold during the molding process using numerical simulation can provide guidelines for determining the optimal molding parameters. The authors have previously proposed a coupled analysis method of "fluid analysis and temperature analysis using MPS (Moving Particle Simulation) method, and magnetic field analysis using magnetic moment method." The objective of this study is to assess the solidification process of resin on the mold surface, utilizing a rectangular-shaped mold model

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