The full name of the closed type of plastic molding machine. It is one of the main equipments for plastic compounding. According to the principle of work can be divided into two types of intermittent and continuous. The main structural parameters of the mixer are the rotation speed, diameter, length of the rotor and the total capacity of the mixer. Figure 1 shows the structure of an oval rotor type intermittent mixer. It is composed of a refining chamber, a rotor, a top bolt (pressing device), a bottom bolt (unloading device), a heating and cooling device, and a transmission system. Its working principle is: the mixture enters the smelting room from the hopper, and is subjected to changing shearing and pinching in the gap between two relatively rotating rotors, the gap between the rotor and the mixing chamber wall, and the gap between the rotor and the top and bottom spigots. Smelting and friction, plastic heat and plasticizing, and mixing. Batch mixers have become more standardized and serialized. Commercial mixers are available in sizes of 4, 25, 50, 75, 150, 250, 380l, etc. according to total capacity. Since the intermittent mixer was not suitable for continuous production, a continuous mixer was developed in the 1960s. More commonly used are rotor-type continuous mixers and twin-screw mixers. There are many types of twin-screw kneading machines. Generally, it has the material forcibly conveying capacity, strong mixing function, the short residence time of the material in the twin-screw, and the self-cleaning performance of the twin-screw is good. It can eliminate accumulated material in time and reduce the material degradation phenomenon, so the application is increasingly popular. Figure 2 is a twin-screw compounding-pelleter.