Abstract: This research focused on water penetration behavior in water-assisted injection molding process with the help of a newly developed water injection system by the author's lab and visualization technology. A flow visualisation mold of rectangular cavities with dimensional variations and curved sections,.was specially designed and made for this study. The material used was Polystyrene. The water-assisted melt filling processes on different water pressures were also observed during water-assisted injection molding. It was found that the water penetration behavior is a turbulent jet after water penetrates the high-viscosity melt which is caused by the cooling of the water injector. Water jet penetration length increases with water pressure increasing. When water pressure is low, water is inclined to change its penetration direction. The higher water pressure is, the more smooth water channel will be. The water front gradually contracts in the inlet of the curved section and at the contractional transitons, while expanding in the outlet of the curved section and at the expansional transitons.

Key words: water assistance, visualisation, water penetration, dimensional variations section, curved section, injection molding