hrough the to-and-fro movement of plunger therein, and the spreader further injects them into the mold cavity through the nozzle. The plastication of plastics in the charging barrel mainly depends on the heat provided by the outer heater of charging barrel. The poor thermal conductivity of plastics results in the unbalanced plastication to the inner and outer layer of materials in the charging barrel and therefore, the plunger injection molding machine is not suitable for the molding of plastic parts with low fluidity. strong heat sensitivity and overlarge amount of injection 2)Screw Injection Molding Machine 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 The course of injection and molding of plastics is a cycling process, wherein the completion of one cycle represents the completion of one injection cycling period. Each period mainly comprises quantitative feeding, fusion and plastication, pressurization and injection, mold filling and cooling as well as mold opening and taking out the parts etc. The next cycle follows after the plastic parts have been taken out and the molds have been closed. The completion of each injection cycling period represents the completion of a working cycle for the injection unit and mold clamping unit of the injection molding machine, namely, each moving part of the two units has moved once according to the scheduled The cycling process is indicated in Fig. 6-2 Plastication Raw materials 塑料原料一预塑 主座后退 注座前进 Injection unit moving backward Injection unit moving forward 具预热 计量 Preheating mold 插嵌件一闭校一 清理模具← 顶出塑 Opening mold Clear-up mold Pressure maintaining Fig6-2: cycling process of plastic injection molding Three stages shall be needed for the completion of injection and molding: plastication, injection and mold 1)Plastication Ejecting parts The raw materials of plastics fall into the charging barrel from the hopper and are sent forward by the rotating screw. While in the charging barrel, the plastics, on the one hand, receive heating and warming from outside of the barrel, and on the other hand, are compacted due to the gradual reduction of the volume of spiral flute. Meanwhile, strong stirring and cutting shall be applied to the plastics by the rotation of screw in the charging barrel, resulting in the intense friction between plastics and between plastics and the barrel as well as screw, and producing a lot of heat which leads to the gradual plastication and fusion of plastics while being pushed forward. The screw while rotating also movesthrough the to-and-fro movement of plunger therein, and the spreader further injects them into the mold cavity through the nozzle. The plastication of plastics in the charging barrel mainly depends on the heat provided by the outer heater of charging barrel. The poor thermal conductivity of plastics results in the unbalanced plastication to the inner and outer layer of materials in the charging barrel and therefore, the plunger injection molding machine is not suitable for the molding of plastic parts with low fluidity, strong heat sensitivity and overlarge amount of injection. 2) Screw Injection Molding Machine 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. The course of injection and molding of plastics is a cycling process, wherein the completion of one cycle represents the completion of one injection cycling period. Each period mainly comprises: quantitative feeding, fusion and plastication, pressurization and injection, mold filling and cooling as well as mold opening and taking out the parts etc. The next cycle follows after the plastic parts have been taken out and the molds have been closed. The completion of each injection cycling period represents the completion of a working cycle for the injection unit and mold clamping unit of the injection molding machine, namely, each moving part of the two units has moved once according to the scheduled sequence. The cycling process is indicated in Fig.6-2. Fig.6-2: cycling process of plastic injection molding Three stages shall be needed for the completion of injection and molding: plastication, injection and molding. 1) Plastication The raw materials of plastics fall into the charging barrel from the hopper and are sent forward by the rotating screw. While in the charging barrel, the plastics, on the one hand, receive heating and warming from outside of the barrel, and on the other hand, are compacted due to the gradual reduction of the volume of spiral flute. Meanwhile, strong stirring and cutting shall be applied to the plastics by the rotation of screw in the charging barrel, resulting in the intense friction between plastics and between plastics and the barrel as well as screw, and producing a lot of heat which leads to the gradual plastication and fusion of plastics while being pushed forward. The screw while rotating also moves Raw materials Injection unit moving forward Preheating mold Insert Plastication Injection unit moving backward Measurement Closing mold Parts Clear-up mold Opening mold Injection Pressure maintaining Ejecting parts