When using a twin-screw extruder, many friends may not be aware of its temperature control, which can lead to the inability to meet the required temperature during the production process and affect the quality of the output. So, how should its temperature be controlled? It is mainly controlled based on the temperature of the feeding port, melting section, and homogenization section. In the article, the editor will provide a detailed introduction to the temperature control of twin-screw extruders and the correct startup steps.
Temperature control of twin-screw extruder:
1. Temperature at the feeding port
At the inlet of the feeding section, the temperature needs to be lower to prevent the resin from sticking and blocking the feeding port. Additionally, in the feeding section, the resin is constantly compressed and air needs to be discharged backwards from the feeding port. Depending on the twin-screw extrusion mechanism, the temperature at the feeding port is approximately 50-90 degrees. The temperature at the inlet is 50-90 degrees, and the end is equal to the melting point or viscous flow temperature. On this section, it can be set as a temperature proportional linear heating.
2. Melting section temperature
At the beginning of the melting stage, the temperature reaches the viscous flow temperature before melting. For crystalline resins, the viscous flow temperature is equal to the melting point temperature. Then, by continuously tightening and increasing the melt layer, the temperature of the twin-screw extruder needs to be continuously increased in order to make the resin molecular chains of different lengths and the polymers with different thermal motion energies melt successively. Therefore, after the temperature at the end of the melting section is established, it can be determined that other parts of the section are linearly heated.
3. Temperature of homogenization section
In the homogenization stage, the main processes are remelting homogenization and quantitative constant pressure constant temperature output of the melt. The temperature in this stage should be kept stable, or the temperature at the end of the melting stage should slightly increase. For blown film, it is required that the temperature of the first stage be lower, but not lower than the viscous flow temperature, in order to facilitate the lifting and normal blowing of the twin-screw extruder.
The startup steps of twin-screw extruder:
1. Heat the twin-screw extruder to keep the temperature of the body, head, die, and control points within the specified range.
2. If the machine is stopped for a long time and then restarted, it needs to be kept at a constant temperature for 10-30 minutes after the heating temperature at each point reaches the target range. If the machine is stopped for half an hour and restarted, it does not need to be kept at a constant temperature.
3. Start the air compressor and stop for backup when the pressure in the storage cylinder is 6-8 kg/cm.
4. According to the requirements of film bending diameter and thickness, operate the production capacity of the twin-screw extruder for processing, estimate the traction speed and stable bubble diameter.
5. After the temperature at each point meets the requirements, put on personal protective equipment and start the tractor, blower, and extruder in order.
6. Check the thickness and width of the film at various locations of the plastic blown film machine, and adjust them to meet the requirements.
7. When the discharge from the mold is uniform and consistent, you can wear gloves and slowly lift the tube blank, while sealing the end of the tube blank and blowing a small amount of compressed air from the center hole of the core rod.
The above is the introduction by the editor about the temperature control of twin-screw extruders and the correct startup steps. I hope this article can help you better understand this industry.