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Advances in Materials Science and Engineering
Volume 2014, Article ID 238251, 6 pages
Research Article

A Study on the Void Formation in Residual Wall Thickness of Fluid-Assisted Injection Molding Parts

1Molding & Forming Technology R&D Group, Korea Institute of Industrial Technology, 7-46 Songdo-dong, Yeonsu-gu, Incheon 406-840, Republic of Korea
2Department of Mechanical Engineering, Ajou University, San 5 Woncheon-dong, Yeongtong-gu, Suwon, Kyungki-do 443-749, Republic of Korea
3Department of Manufacturing Engineering, University of Texas Pan-American, Edinburg, TX 78539, USA

Received 23 December 2013; Accepted 22 April 2014; Published 9 June 2014

Academic Editor: Mohd Sapuan Salit

Copyright © 2014 Hyung-Pil Park et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In fluid-assisted injection molding, the distribution of the residual wall thickness on the inside and outside of the curved area is different, and void is formed due to the effect of the shrinkage on the outside where the residual wall thickness is thicker. The shrinkage that takes place in the residual wall is affected by the rheological changes in the polymer caused by temperature change and also by the thermal properties of the penetration fluid. In this study, the different effects on void formation in residual wall during fluid-assisted injection molding were analyzed, and water and silicone oil that had different thermal properties were used for the fluids. For this, heat transfer analysis and injection molding analysis were conducted. The void formation occurred due to the different temperature distribution and volumetric shrinkage in the direction of the residual wall in the curved area with a hollow section. It was also found that the void formation in the curved area decreased in the case of silicone oil compared to the case of water from simulation and experiments.