Characteristics of gas penetration and polymer melt flow in gas‐assisted injection molded spiral tubes was investigated by simulations and experiments. Distribution of the skin melt thickness along the gas flow direction was measured, and gas penetration in the primary and secondary stages was identified. An algorithm based on the control‐volume/tiniteelement method combined with a particle‐tracing scheme using a dual‐filling‐parameter technique is utilized to predict the advancements of both melt front and gas from during the molding process. The simulated distribution of gas penetration shows reasonably good coincidence with experimental observations. © 1995 John Wiley & Sons, Inc.

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Erperimental shrdies of polymer mekj7uw in the moldJiUing stage of the coinjection molding process have been carried ouf using sequenliol injection of lra~parenf and colored polystyrene resin. Simuhtions are also developed to predict the meN fronl uduancemertls of both skin and core meh. A control uolume/Jinife elemenl method employed within eoch grid hyer of the gapwise direction is applied lo trace the mek front advancements for both skin and core materiuls. Numerical sirnulolions show reasonnlily good consistency wifh experimenlal results in both skirr and core mulerid distribution. Howeuer, the sirnulolion accumcy can be improuedfurther i f edge eflect is &ken into m o u n t using the shape factor as a geometrical correction.

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