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Conflict of Interest: In relation to this article, we declare that there is no conflict of interest.

Publication history: Received April 3, 2003
Accepted December 10, 2003

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Flow Direction When Fan Shaped Geometry is Applied in Gas-Assisted Injection Molding: 1. Flow Model Theory and its Criteria for Predicting Flow Directions

Kwang-Hee Lim^†

Department of Chemical Engineering, Daegu University, Kyungsan, Kyungbuk 712-714, Korea

khlim@daegu.ac.kr

Korean Journal of Chemical Engineering, January 2004, 21(1), 48-58(11), 10.1007/BF02705380

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Abstract

In part 1 of this paper a qualitative analytical method to predict the preferred gas flow direction in gasassisted injection molding (GAIM), which involves flow through panel-areas of various fan-shaped geometries, and the criteria to apply the method were presented with appropriate assumptions. Then the definition of a resistance to initial velocity was proposed as a rule of thumb, by which the gas directions of GAIM were predicted under various fan-shaped geometries. Upon performing the simulation on them with commercial software (MOLDFLOW), we compared_x000D_ the ratio of simulated gas penetration lengths to both directions with the predicted ratio of resistances as well as the predicted direction of the gas flow in GAIM using the suggested rule of thumb herein presented. The predictions with the suggested rule of thumb were generally quite consistent with the results of simulation (MOLDFLOW). However the discrepancy between the ratio of gas penetration lengths and the ratio of resistances was observed to increase as the ratio more{(H/R₀)(one-side)/less(H/R₀)(the other-side)}of the values of H/R₀ on both sides of fan-shaped cavities became bigger even though the suggested rule of thumb was assumed adequate to use until the case met the condition of (H/R₀)² 1/θ² << 1 and (H/R₀)² << 1. Nevertheless, the suggested rule of thumb was still effective as far as the direction of gas flow was concerned.

Keywords

Fan-shaped Geometry Direction of Gas Flow Gas-Assisted Injection Molding Gas Penetration Length A Rule of Thumb Simulation

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