Flow Patterns and Water Penetration in Water-assisted Melt Filling Using an Emulated Mold

Water-assisted injection molding (WAIM) provides a new way to produce hollow plastics parts and reduce production costs. The melt flow behavior when applying high pressure water has an important effect on the water penetration length and residual wall thickness of molded parts. So the purpose of this study was to visualize the flow patterns of melt and to characterize the water penetration behavior under applying high pressure water. The experimental setup mainly consisted of a water injection unit, a water injector, and an emulated mold. A circular mold cavity was filled alternately with red and green polymer tablets. The mold was heated long enough to make these tablets melt completely. After a delay time, water was injected into the melt to fill the cavity. The flow patterns of the polymer melt were visualized on the molded samples. The influences of process parameters on the melt flow, water penetration length, and residual wall thickness were investigated. The process parameters varied in experiments included initial filling, melt temperature, water delay time, and water pressure. It was demonstrated that the initial filling was the most significant factor affecting the water penetration.