Four Factors Affecting Plastic Pipe Extrusion

The plastic extruder can be used with various plastic molding auxiliary machines such as pipes, films, holding materials, monofilaments, flat filaments, packing belts, extrusion nets, plates, profiles, pellets and cable coatings. Plastic pipe extrusion machine is one of the widely used machines in the plastic processing industry.

Extrusion process parameters include temperature, pressure, extrusion rate, and traction speed.

1.Temperature

Temperature is one of the important conditions for smooth extrusion. Starting from powdery or granular solid materials, high-temperature products are extruded from the head and undergo a complex temperature change process. Strictly speaking, the extrusion molding temperature should refer to the temperature of the plastic melt, but this temperature largely depends on the temperature of the barrel and the screw. This should be especially paid attention among China high speed PE PPR pipe extrusion lines.

The head temperature must be controlled below the thermal decomposition temperature of the plastic, and the temperature at the die can be slightly lower than the head temperature, but the plastic melt should have good fluidity. In addition, temperature fluctuations and temperature differences during the molding process will cause defects such as residual stress, uneven strength at various points, and a dull and matte surface.

2. Pressure

As with temperature, pressure changes with time will also produce periodic fluctuations. Such fluctuations also have adverse effects on the quality of plastic parts. Changes in screw speed, instability of heating and cooling systems are all causes of pressure fluctuations. Many double wall corrugated pipe extrusion machine suppliers ignored this point and made mistakes in manufacturing. In order to reduce pressure fluctuations, the screw speed should be controlled reasonably to ensure the temperature control accuracy of the heating and cooling devices.

3. Extrusion rate

There are many factors that affect the extrusion speed, such as the structure of the head, screw and barrel, the speed of the screw, the structure of the heating and cooling system and the characteristics of the plastic. Both theory and practice have proved that the extrusion rate increases with the increase of the screw diameter, the depth of the spiral groove, the length of the homogenization section and the speed of the screw, and increases with the melt pressure at the end of the screw and the gap between the screw and the barrel. When the structure of the extruder and the type of plastic and the type of plastic parts have been determined, the extrusion rate is only related to the screw speed. Therefore, adjusting the screw speed is the main measure to control the extrusion rate.

4. Traction speed

Extrusion mainly produces continuous plastic parts, so traction devices must be provided. The plastic parts extruded from the die and die will be stretched and oriented under traction. The higher the degree of tensile orientation, the greater the tensile strength of the plastic part along the orientation direction, but the larger the length shrinkage after cooling. Generally, the traction speed can be comparable to the extrusion speed. The ratio of traction speed to extrusion speed is called the traction ratio, and its value must be greater than 1.