The stage of the injection molding cycle when pressure is applied to the polymer melt to compress the polymer and to force more material into the mold. This compensates for the shrinkage that occurs as the polymer cools from the melt temperature to ambient temperature (hours or even days after the part has left the mold). From 5 percent to 25 percent more material is added to the mold during the packing stage. The gate should freeze during the packing time to prevent material from exiting the mold.