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우상원(S. W. Woo),최두선(D. S. Choi),유영은(Y. E. Yoo),윤재성(J.S. Yoon),김선경(S. K. Kim),조성준(S. J. Cho) 한국소성가공학회 2012 금형가공 심포지엄 Vol.2012 No.9
Surface defects such as silver streak is one of the common surface defects in injection molding of plastic part. Drying the material before molding to eliminate the moisture is one of the most typical ways to remove this defect. This pre-drying process, however, consumes too much energy generally and also cannot eliminate the surface defects perfectly, consumption of energy, this method cannot meet the requirement for quality of the molded part. In this study, an alternative way for this drying process is proposals, which is to pre-pressurize the mold cavity before molding. A pressurizing equipment and mold is made to investigate the effect of the new process on the surface quality and the mechanical properties of the injection molded specimen.
우상원(S.W. Woo),유영은(Y.E. Yoo),최두선(D.S. Choi),윤재성,김선경(S.K. Kim),조성준(S.J. Cho) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Vaporized moisture in the thermoplastic resin has caused surface defects such as silver streak. Pre-drying process to eliminate the moisture from the resin is a typical way to reduce the surface defects from the moisture, but it results in great increase of energy consumptions. As an alternative way for this drying process, pre-pressurized cavity of injection molding tool was proposed and proved to reduce the surface defects without pre-drying process for resin. The effect of this new process depends on the pressure of the pre-pressurized cavity by inert gas like air or nitrogen gas, because the vaporization of the moisture in the resin is determined by the temperature and the pressure of the environment. In this paper, the pressure of the cavity is measured during the injection molding process for different pressurized gas being delivered to the cavity. Due to the cavity volume and leakage from the injection molding tool, the pressure of the cavity varies for quite long time considering the very quick filling process of the injection molding and also is limited to maximum pressure quite lower than pre-set value. The data from a series of experiment has been applied to designing the injection mold tool structure and cavity pressurizing system.