Abstract: A frequent problem encountered in gas-assisted injection molding(GAIM) is gas fingering, i.e. gas bubbles penetrating outside designed gas channels and forming finger-shaped branches. Severe gas fingering will result in reduction of part strength, failure of gas-assisted injection molding or cancellation of the advantages of GAIM. Gas fingering defects in GAIM parts are investigated with the methods of numerical simulation and orthogonal experiment. Six process parameters that have the most important influence on gas fingering defect are studied, i.e. shot size, gas delay time, gas injection pressure, mold temperature, melt temperature and gas injection time. The results show that the most important process parameters that influence gas fingering are gas delay time, melt temperature and gas injection pressure successively. Therefore, to choose reasonable gas delay time, melt temperature and gas injection pressure is particularly important. For reducing the degree of gas fingering, it is suggested that at the same melt temperature the gas delay time should be appropriately prolonged.

Key words: Gas fingering, Gas-assisted injection molding, Numerical simulation, Orthogonal experiment