The core of calibrating a hot runner sensor after aging is compensating for the deviation caused by aging. The calibration process differs slightly from that of a brand new sensor and involves four steps:
1. Pre-treatment (Eliminating Non-Aging Interference)
First, remove the sensor and clean the surface of the sensing diaphragm, removing any accumulated material and residual corrosion. Gently scrape away any adhering substances with a soft copper sheet, being careful not to damage the diaphragm. Then, reinstall it in the hot runner and heat it to the normal production temperature, holding it at that temperature for 30 minutes to allow the sensor to reach thermal stability.
2. Zero-point Calibration (Correcting Zero-Pressure Deviation)
Completely depressurize the system to zero melt pressure in the runner. After 10 minutes of stable output:
Adjust the current sensor output to the standard zero point (generally 4mA corresponds to zero pressure). Write the current zero-point deviation into the injection molding machine control system to complete the zero-point compensation.
3. Full-Scale Calibration (Correcting Sensitivity Deviation)
Increase the injection molding machine pressure to 80% of the sensor's range, hold the pressure until it stabilizes, and wait for the output to stabilize.
Record the actual output value of the sensor and compare it with the theoretical output value. Compensate for the deviation in the system to ensure the output matches the theoretical value.
4. Verification and Tracking
After calibration, repeat the "pressure release → pressure increase and holding" process three times consecutively to confirm that the output deviation is within the acceptable range. After aging the sensor, it is recommended to retest the deviation every two weeks to detect any drift exceeding the standard.
Note: If the deviation still exceeds twice the nominal accuracy after calibration, it indicates that aging is irreversible and calibration cannot correct it; replacement is necessary.
