Plastic pipe extrusion die structure
2022-08-01
The extrusion molding head is an important component in the extrusion molding production line. Its function is to further compact and plasticize the plasticized melt. After being split, it enters the annular cross-section flow channel and cools to form a tube blank. Pipe extrusion heads are divided into three types: straight-through head, right-angle head (also known as elbow head) and side head (side head). Among plastic pipes, polyvinyl chloride pipes have the largest output and the widest application, of which rigid polyvinyl chloride pipes account for 75% and soft polyvinyl chloride pipes account for 25%. The following is a further introduction to the PVC pipe head.
1. Straight-through head
The axis of this type of head coincides with the axis of the extruder, and has the advantages of simple structure, easy manufacture, low cost, and low material flow resistance; this type of head has difficulties in heating the core mold when producing pipes with large outer diameter and sizing. , The shortcomings of the pipe at the seam line caused by the shunt bracket are low. It can be seen from the runner structure that when the fluid passes through the machine head, it goes through several stages, such as shunt, compression, stable flow, and shaping. Here, L is the length of the straight part of the die, L2 is the length of the compression section, and L is the shunt cone. .
2. Right-angle head
The mandrel end of this structure is the support end. Since there is no diverter bracket, the molten material enters from the head end to the opposite side of the mandrel and gathers, which may only produce a seam line. In addition to pipes, the right-angle head can also produce wire and cable products, which has the advantages of easy heating of the mandrel and suitable for extruding pipes by the inner diameter setting method; however, it also has the advantages of complex structure, difficult mandrel design, high manufacturing cost, material Disadvantages such as large flow resistance.
3. Lateral nose
The material flow from the extruder first flows through a curved flow channel, and then enters the side of the machine head, and then flows out along the direction of the machine head axis after wrapping the core rod. This design can not only make the extrusion direction of the pipe material at any angle with the extruder, but also parallel to the screw axis of the extruder, which is suitable for high-speed extrusion of large-diameter pipes, but the head structure is relatively complex and the cost is high.
4. Other forms of head
Other types of heads include sieve plate extrusion head, coated pipe head, coated pipe head, mandrel rotary head and so on. The mandrel rotary head uses ordinary polymer particles to mix glass fibers of a certain length online after plasticizing and melting, and make the melt molecules and glass fibers spirally oriented along the wall of the extruded circular pipe. , to produce higher strength pipes to meet the actual needs of the project.