2. Design of runner. 1).Mainstream channel design. The main channel is usually located at the entrance of the plastic melt at the center of the mold, which is injected into the flow channel or cavity of the injection mold. The sprue is in a conical shape, so that the melt flow and mold sprue pulling out smoothly. 2).Design of diversion channel and cold material well. Due to the use of the nozzle plate, the diversion channel must be made into a trapezoidal cross section, which is convenient for the diversion channel and the mainstream way.