Abstract: In order to formulate the controlling model of the gas assisted controlling unit, experiments on the influence of processing parameters in the ga、一assisted co-injection molding were investigated in this paper. It showed that the gas packing time and gas delay time affected the gas penetrating pattern
appreciably, but not the melt at the core layer. With increasing gas packing time, the gas penetrating depth and width increased，with increasing gas delay time, gas penetrating depth increased，the gas penetrating width reduced，however, the instability of gas penetrating flow and finger appearance were observed.

Key words: gas assisted co-injection molding, process parameter, experimental research