What problems will be caused by inaccurate temperature control of engineering plastic extrusion production line? How to adjust it?

1. Problems caused by inaccurate temperature control
Material degradation or performance degradation-
Temperature is too high: When the temperature of the engineering plastic extrusion production line exceeds the decomposition temperature of engineering plastics (such as FEP, PVC, etc.), it will cause molecular chain breakage, discoloration, bubbles or mechanical property degradation.

Temperature is too low: The melt has poor fluidity, the engineering plastic extrusion production line is difficult to extrude, and cold flow lines or cracks are prone to appear on the surface of the product. For example, PVC extrusion at low temperature may cause excessive load on the front-end mechanism.

Product size and shape defects: Temperature fluctuations can cause changes in melt viscosity, resulting in unstable extrusion rate, which is manifested as uneven pipe wall thickness (such as large longitudinal wall thickness error) or deformation of profiles. Uneven head temperature may also cause circumferential wall thickness error, affecting concentricity.

Equipment and energy consumption issues-
Inaccurate temperature control may cause abnormal current of the main motor (such as increased torque due to heater failure) or increased screw wear. Frequent temperature corrections will increase energy consumption and reduce production efficiency.

2. Methods for accurate temperature adjustment
Optimize temperature control system hardware
PID controller calibration: Use proportional-integral-differential (PID) algorithm to reduce temperature fluctuations by adjusting the proportional band (P), integral time (I) and differential time (D). First adjust the P value to stabilize the basic response, then eliminate the residual error through the I value, and finally use the D value to suppress overshoot.

Sensor selection: Use fast-response thermocouples or infrared sensors to ensure that the actual temperature and the set value deviation are ≤±2℃.

Segmented temperature control and process matching
Segmented control: Divide the extruder into heating section, constant temperature section and insulation section, and set the temperature for different sections. In PVC processing, the feeding section and metering section need to be controlled to avoid imbalance between internal heat (shear heat) and external heat.

Material adaptation: Adjust parameters according to different plastic characteristics. For example, the extrusion temperature of FEP needs to be strictly controlled between 304℃~392℃ to avoid decomposition.

Dynamic adjustment and maintenance
Cooling system coordination: balance friction heat through water cooling or air cooling. For example, the feeding area of ​​the twin-screw extruder needs to be cooled to prevent premature solidification of the material.
Regular maintenance: clean the heating elements and sensors, check the screw wear, and avoid temperature control failure due to equipment aging.

Intelligent control technology
Adaptive algorithm: use fuzzy logic or neural network to optimize PID parameters in real time to adapt to nonlinear changes in production.
Data monitoring: integrate the Internet of Things (IoT) system to track the temperature curve in real time and warn of abnormalities.

3. Typical cases and precautions
PVC extrusion: Excessive temperature will cause melt rupture, which needs to be alleviated by reducing the screw speed and adjusting the mold pressure.
FEP processing: Excessive material temperature is prone to bubbles, and the cooling water flow needs to be increased and the mold structure needs to be optimized.
Maintenance tips: calibrate the temperature control system once a month and replace damaged heating coils or thermocouples.