The screw injection molding machine differentiates from the plunger injection molding machine mainly in that the horizontally-pushed plunger in the charging barrel is replaced by a rotary screw which undertakes all the fusion, plastication as well as injection of the materials in the charging barrel.The screw can not only rotate in the barrel but also can move forward and backward, and thereby is able to achieve such functions as sending materials, compacting, plasticating and transmitting pressure. Currently, the screw injection molding machine yields the highest productivity and is also the most widely applied. As indicated in Fig.6-1 is a complete set of super-luminous and traceless injection molding system, wherein Yanhing SP108A injection molding machine is one of the screw type. The subsequent discussion shall be based on the screw injection molding machine.