1. Temperature setting principle
Feeding section temperature:
The main function of the feeding section is to convey solid plastic into the screw and start preliminary heating and softening. The temperature of this section should not be too high, and is generally set in a range close to the softening temperature of the plastic but below the melting temperature.
For example, for most general plastics, the feeding section temperature can be set at about 20℃ to 50℃ lower than its melting temperature.
Compression section temperature:
The compression section is the area where the plastic is further softened and compressed, and in this section the plastic gradually changes from a solid state to a molten state. Therefore, the temperature of the compression section should be gradually increased to promote the melting and mixing of the plastic.
The temperature of the compression section is usually about 20℃ to 50℃ higher than that of the feeding section.
Homogenization section temperature:
The main task of the homogenization section is to make the plastic melt reach a uniform temperature and composition to prepare for extrusion molding. The temperature of this section is usually set at a level slightly higher than the melting temperature of the plastic to maintain good fluidity and stability of the plastic melt.
The temperature fluctuation of the homogenization section should be as small as possible to ensure uniform quality of the extruded product.
2. Monitoring and adjustment
Real-time temperature monitoring:
Use high-precision temperature sensors and control systems to monitor the temperature of each heating section in real time and make fine adjustments based on feedback.
Ensure that temperature sensors are installed in key locations, such as barrels, die heads, and molds.
Temperature control system:
Use PID control system to automatically adjust the heating and cooling systems to maintain the set temperature based on the temperature value fed back by the temperature sensor.
In the temperature control system, set the appropriate temperature range and deviation value to ensure temperature stability.
Regular calibration:
Regularly calibrate the temperature sensor and control system to ensure the accuracy of measurement and control.
During the calibration process, a standard temperature source can be used for comparison to ensure the accuracy of the sensor.
3. Optimization measures
Adjust the screw speed and feed rate:
Under certain conditions of the extruder screw speed, adjust the shear heat by increasing or decreasing the feed rate.
Reducing the feed rate can reduce the shear heat, but be careful not to reduce the material temperature in the feed section.
Cooling system coordination:
When necessary, use cooling devices such as oil cooling or water cooling to transfer excess shear heat in the metering section.
Ensure that the cooling system can effectively absorb heat to avoid local overheating.
Optimize screw design:
Appropriately increase the gap between the screw fins in the metering section to adapt to high-speed extrusion and reduce shear heat.
