Abstract: The effects of the gas channel geometry in the gas-assisted injection molding on the gas fingering defect of the part made of polystyrene were investigated. The semicircular gas channels with different radiuses, the rectangular gas channels with different section width-to-length ratios, and the four gas channels with different cross section shapes but with same section area were studied. In the case of the semicircular channels, a minimum gas fingering defect was observed when the ratio of the section equivalent radius to the part thickness is in a certain range. For the rectangular channels, the gas fingering defect appears the most severe at a certain definite section width-to-length ratio. For the four gas channels with different section shapes, the channel with ribs appears to be better than that without ribs in respect of the gas fingering defect.

Key words: gas-assisted injection molding, finished product, gas-fingering, numerical simulation