The word "extrude" of plastic extrusion die principle consists of Latin words "ex" and "trudere", which vividly describes the extrusion process of "applying pressure to drive the material to form through the die". During the processing of ZOJE extrusion die, polymers are usually added to the extruder barrel in the form of powder or particles. Under the action of screw or plunger, the polymer moves forward along the screw groove or barrel and gradually melts into viscous fluid. Then, through the die set at the end of the cylinder, a continuous body with a shape similar to that of the die is formed. Finally, after cooling and shaping, the product can be molded into the required shape. Such as plastic pipes, strips, sheets, plastic doors and windows, films, decorative skirting boards, etc. The overall design point of plastic extrusion die is the core part of extrusion production, and the technical state of extrusion die is directly related to the stability of extrusion production, the quality of extruded products, the efficiency of extrusion production and the service life of the die itself. Therefore, the design of extrusion die is very important. Pay attention to the following points when designing dies: 1. The inner cavity of the mold should be streamlined. In order to make the material extrude evenly along the die channel and avoid overheating and decomposition due to stagnation, the die must not shrink sharply, and there must be no dead angle and stagnation area. The chute should be as smooth as possible. It is suggested that the surface roughness Ra value is 0.4μm2. Adequate compression ratio should be designed according to different plastic products and varieties. 3. Correct cross-sectional shape Due to the influence of plastic properties, pressure, density, shrinkage and other factors, the cross-sectional shape of the mold is different from the real cross-sectional shape of the product. This factor should be considered in the design to make the die head of the die have a reasonable cross-sectional shape. 4. Compact rhythm and convenient disassembly. Under the condition of satisfying the mechanical properties, a die with compact rhythm, uniform heat transfer, convenient disassembly and assembly and no material leakage is designed. 5. Reasonable material selection The die should be made of steel with corrosion resistance, friction resistance, good tensile strength and high hardness. Some need chrome plating according to the situation.