The movement of the material in the screw of the extruder is divided into three sections, so that the design of the screw is often carried out in sections. Since each section is a continuous channel, in actual production, as long as it can meet the requirements, it is not necessary to divide the screw into three sections. In fact, there are only two sections of the screw, and some are not segmented. For example, when extruding a material with good crystallinity such as nylon, only the feed section and the homogenization section, and the general screw-extruded soft PVC plastic screw, can use the entire compression section without being divided into the feed section and the feed section. Sections. The segmented type of screw obtained from experience mainly depends on the nature of the material. The length of the feed section can range from 0 to 75% of the total length of the screw. Generally speaking, the longest is the extrusion of the crystalline polymer, the hardest amorphous polymer is the next, and the soft amorphous polymer is the shortest. The length of the compression section usually accounts for 50% of the total length of the screw, except for the above-mentioned nylon and soft PVC plastics. When the polyethylene is extruded, the length of the homogenization section can be 20 to 25% of the total length. However, for some heat-sensitive materials (such as polyvinyl chloride), the material should not stay too long in this section, you can not homogenize the length of some high-speed extruder homogenization section actually take 50%.