I. Temperature Signal Anomaly Judgment:
The temperature controller reading exhibits irregular fluctuations of ±2℃ or more, and investigation confirms that it is not caused by thermocouple or temperature sensing wire malfunction.
During the heating process, there is a significant temperature sampling lag; the actual flow channel temperature has reached the set value, but the temperature controller reading still lags by more than 2 seconds.
The temperature control curve exhibits unexplained small oscillations, with an overshoot exceeding 5℃, which cannot be eliminated even after PID parameter tuning.
II. Hardware and Environmental Change Judgment
The workshop has added high-power frequency converters, servo motors, and other strong interference sources, significantly altering the on-site electromagnetic environment.
The hot runner temperature sensing wires, connectors, and temperature controller input ports have been replaced or rewired, changing the signal link impedance.
The preset period threshold (6 months for normal scenarios, 3 months for precision scenarios) has been reached since the last RC parameter calibration.
III. Performance Index Measurement Judgment
Using an oscilloscope to measure the filtered output, the attenuation of the target interference signal is less than 15dB, far below the initial calibration standard of ≥20dB.
The measured RC filter cutoff frequency deviated from the set value by more than 20%, indicating parameter drift exceeding the allowable range.
The measured RC total time constant exceeded 200ms, indicating excessive temperature measurement signal delay and a risk of temperature overshoot and runaway.
IV. Production Process Anomaly Judgment
Under the same process conditions, the product yield suddenly declined for no apparent reason, and investigation confirmed that the materials, heating coils, and PID parameters were all normal.
Switching to process highly biodegradable and sensitive materials (PVC, POM, etc.) significantly increased the requirements for temperature stability, and the original RC parameters could not meet the requirements of the new scenario.
