The actual distribution of the plastic melt in the die runner is determined by the flow properties of the melt, the geometry of the runner, the flow rate through the die, and the temperature distribution in the die. If the required flow channel geometry of a plastic has been optimized under a set of conditions, simply changing the transmission rate or temperature can affect the optimized flow channel geometry. In addition to the circular die, it is very difficult to obtain a reasonable flow channel geometry in terms of a variety of plastics and operating conditions. Therefore, usually when the extruder is running, the extrusion die is given the ability to adjust, and its distribution is changed from the outside, such as setting a flow blocking or restricting component in the die, and changing the local die temperature The mechanical design tends to be complicated, but the flexibility and controllability of the die head are improved. The general requirements for the design of the die head are: no dead angles in the runner, the speed along the runner is steadily increased, easy assembly and disassembly, the length of the die shaping section is about 10 times the gap of the die, the geometry of the runner should not be changed and adopted Small asymptotic angle.

       Extrusion die heads are mostly made of steel, which requires pressure resistance, high temperature resistance, wear resistance and chemical corrosion resistance; sufficient toughness and surface hardness; easy polishing, electroplating, small heat treatment deformation; good thermal conductivity; no stress. Commonly used steels are carbon structural steel, carbon tool steel, alloy structural steel and alloy tool steel. Manufacturing methods include mechanical cutting, electrical corrosion processing, and high-energy electron beam processing.