How to Calibrate a Hot Runner Sensor After Aging

The main goal of calibrating a hot runner sensor after aging is to make up for the age-related variance. There are four steps in the calibration procedure, which is a little different from using a brand-new sensor:

1. Pre-treatment (Removing Non-Aging Interference)

Remove the sensor first, then clean the sensing diaphragm's surface to get rid of any debris and remaining corrosion. Use a soft copper sheet to gently scrape away any adhering materials, taking care not to harm the diaphragm. After that, put it back in the hot runner and heat it to the standard production temperature. Hold it there for half an hour to give the sensor time to achieve thermal stability.

2. Zero-point Calibration (Zero-Pressure Deviation Correction)

Depressurize the system completely until the runner's melt pressure is zero. Following ten minutes of steady output:

Set the output of the current sensor to the standard zero value, which is typically 4 mA for zero pressure. To finish the zero-point correction, enter the current zero-point deviation into the injection molding machine control system.

3. Full-Scale Calibration (Sensitivity Deviation Correction)

Wait for the output to stabilize after raising the injection molding machine pressure to 80% of the sensor's range and holding it there until it stabilizes.

Keep track of the sensor's actual output value and contrast it with the predicted value. To guaranty that the output corresponds to the theoretical value, make up for the system's departure.

4. Tracking and Verification

To verify that the output deviation is within the permitted range, repeat the "pressure release → pressure increase and holding" procedure three times in a row after calibration. To find any drift that exceeds the standard, it is advised to recheck the deviation every two weeks after the sensor has aged.

Note: After calibration, if the deviation is still greater than twice the normal accuracy, it means that aging is irreversible and cannot be corrected by calibration; replacement is required.