Single-screw extruders are generally divided into three sections in terms of reasonable length. According to the extruder screw diameter, pitch, and screw depth, the reasonable length of the three sections is clearly defined. Generally, each section is divided into one-third.
An external thread of the material port is gradually called the transportation section: the raw material must not be melted here, but must be heated and forced to compact. In the past, the old basic extrusion theory believed that the raw material here is a loose body. Later, it was confirmed that the raw material here is a solid plug. It is here that the raw material is solid like a bottle cork after being extruded, so it is only necessary to carry out daily tasks for transportation.
The second stage is called the reduction stage. At this time, the volume of the screw groove is gradually reduced from large, and the temperature must be at the level of the melting of the raw materials. Here, the reduction is caused by the third stage of the transportation, and the reduction is here to one. This is called the engine compression ratio of the extruder screw. 3:1, some equipment also changes, the raw materials for melting enter the third stage.
The third section is the measurement verification section, where the raw material maintains the melting temperature, and it is only as accurate and quantitatively analyzed as the plunger metering pump to transport the molten raw materials to provide the engine. At this time, the temperature cannot be lower than the melting temperature, generally slightly higher.
