Abstract: A variotherm injection molding technique with steam heating and coolant cooling was simulated by Moldflow. Pressures at injection location and frozen layer of part at different heating time were studied, and the thermal response at surface and cavity of the mold waqs analysed using constructed models. Compared with traditional injection molding, in the variotherm injection molding the mold temperature was increased to a designed value, the melt could easily fill into the cavity under a low injection pressure, and the frozen layer was appeared after the filling stage. As the mold heating time increased from 10 to 15, 25, 40 s, the maximum pressure at injection position was reduced from 87.1 to 84.61, 79.7, 74.4 MPa, respectively. The surface temperature of the part and the mold could be changed through different heating time, and the part surface temperature was simultaneously affected by the heat transfer coefficient.

Key words: steam heating, variotherm injection molding, numerical simulation