In recent years, scientific and technological workers on the plastic molding front have conducted in-depth discussions, research, and practice on how to expand the application scope of injection molding, shorten the injection molding cycle, reduce molding defects, improve the quality of plastic parts injection molding, and reduce production costs. They have achieved gratifying results, and new technologies for molds and injection molding processes have emerged one after another. Here, we will only introduce the increasingly widely used thermosetting plastic injection molding, gas assisted injection molding, precision injection molding, low foaming injection molding, co injection molding, exhaust injection molding, and reaction injection molding.
1、 Overview of Injection Molding Process for Thermosetting Plastics
The application of new injection molding technology in injection molding processing. Although there are many similarities in the injection molding principles and processes of thermosetting and thermoplastic plastics, there are also significant differences between them due to their different chemical properties. The principle of thermosetting plastic injection is to feed the molding material from the hopper of the injection machine into the material cylinder, heat it up, and melt and plasticize it under the rotation of the screw, making it a uniform viscous flow state melt. Through the high-pressure push of the screw, these melts are injected into the high-temperature mold cavity through the nozzle at the front end of the material cylinder at a high flow rate. After a period of pressure maintenance, shrinkage and cross-linking reaction, they solidify into the shape of plastic parts, and then the mold is opened to take out the plastic parts. It is obvious that, in principle alone, the main difference between injection molding of thermosetting and thermoplastic plastics lies in the solidification stage after the melt is injected into the mold. The curing of thermoplastic injection molded parts is basically a physical process of transition from high-temperature liquid phase to low-temperature solid phase, while the curing of thermosetting injection molded parts must rely on cross-linking chemical reactions under high temperature and high pressure. It is precisely because of this difference that the injection molding process conditions of the two are different.

（1） Temperature
(1) Material temperature: Similar to the thermoplastic injection molding process, material temperature includes plasticizing temperature and injection temperature, which depend on the temperatures of the barrel and nozzle, respectively. However, due to the different properties of thermosetting and thermoplastic injection molding processes, there are differences in the temperature requirements for the barrel and nozzle between the two. For thermosetting plastics, Dongguan Machike injection molding manufacturers tend to take a lower value of the barrel temperature in order to prevent early hardening of the melt in the barrel and to take into account that the barrel temperature has less effect on plasticization than the shear friction inside the material. However, when the temperature of the barrel is too low, the melting of the material is slow, and a large amount of frictional heat is generated between the screw and the raw material. This heat is actually more likely to cause early hardening of the melt than when the barrel is at a higher temperature. Therefore, strict control should be exercised over the temperature of the material barrel during production. Usually, the temperature of the barrel is set in two or three stages. When setting in two stages, for different materials, the temperature of the rear stage can be selected within 20~70 ℃, while the temperature of the front stage can be selected within 70~95 ℃. The temperature of the rear stage (for example, when adding materials, the frictional heat between the affected melt and the nozzle hole should also be considered, which is generally a high temperature rise. In principle, it is generally required that the temperature of the melt after passing through the nozzle has good fluidity on one hand, and can be close to the critical value of the hardening temperature on the other hand. This can ensure injection molding and also facilitate hardening and shaping. Therefore, the nozzle temperature is generally set higher than the material temperature. For different materials, the nozzle temperature can be selected and controlled within 75~100 ℃. At this temperature, after passing through the nozzle, the temperature of the melt can reach 100-130 ℃, which may meet the above two requirements.

（1） Temperature
(1) Material temperature: Similar to the thermoplastic injection molding process, material temperature includes plasticizing temperature and injection temperature, which depend on the temperatures of the barrel and nozzle, respectively. However, due to the different properties of thermosetting and thermoplastic injection molding processes, there are differences in the temperature requirements for the barrel and nozzle between the two. For thermosetting plastics, Dongguan Machike injection molding manufacturers tend to take a lower value of the barrel temperature in order to prevent early hardening of the melt in the barrel and to take into account that the barrel temperature has less effect on plasticization than the shear friction inside the material. However, when the temperature of the barrel is too low, the melting of the material is slow, and a large amount of frictional heat is generated between the screw and the raw material. This heat is actually more likely to cause early hardening of the melt than when the barrel is at a higher temperature. Therefore, strict control should be exercised over the temperature of the material barrel during production. Usually, the temperature of the barrel is set in two or three stages. When setting in two stages, for different materials, the temperature of the rear stage can be selected within 20~70 ℃, while the temperature of the front stage can be selected within 70~95 ℃. The temperature of the rear stage (for example, when adding materials, the frictional heat between the affected melt and the nozzle hole should also be considered, which is generally a high temperature rise. In principle, it is generally required that the temperature of the melt after passing through the nozzle has good fluidity on one hand, and can be close to the critical value of the hardening temperature on the other hand. This can ensure injection molding and also facilitate hardening and shaping. Therefore, the nozzle temperature is generally set higher than the material temperature. For different materials, the nozzle temperature can be selected and controlled within 75~100 ℃. At this temperature, after passing through the nozzle, the temperature of the melt can reach 100-130 ℃, which may meet the above two requirements.