Visualization of foaming phenomena in thermoplastic injection molding process

The present study focuses on visualization analysis of foaming mechanisms in foam injection molding process. A novel approach in mold design is introduced to take advantages of concepts such as counter-pressure and mold opening to further extension of expansion range, a visual mold with a rectangular cavity was designed and manufactured to observe the effectiveness of this approach. The mold consists of a main cavity and an over-flow well connected together via a secondary gate of variable sizes. The selected processing parameters were gate width and part thickness. The observation clearly showed the development of melt frontier and gas escape, which were affected by varying the selected parameters. The results showed that the relative bulk density and cell diameter decreased and cell population density increased as the optimum gate width (7mm) was employed.