How to Manually Calibrate a Hot Runner Sensor

I. How to prepare for the examination

Instruments: CNAS calibrated high precision digital temperature monitor instrument (accuracy 0.1℃), 500V Digital Megohm Meter, insulated gloves, high temperature thermal grease, Phillips screwdriver, record book.

Requirements The hot runner heater has removed all possible leakage current; The insulation resistance of all channels is ≥5MΩ; The hot runner has been heated to 320℃ and held for 2 hours; The system has reached a fully stable operation condition without overcurrent or voltage fluctuation alarm.

II. Step-by-Step Manual Calibration Usage

Standard Temp Measurement Point Connection Turn off the system. Gently withdraw the thermocouple probe to be calibrated out of the hot runner sensing hole. Apply a thin, even coat of high temperature oil on the probe surface.

Insert the probe back into the bottom of the detecting hole such that the probe has full contact with the metal body of the runner and no gaps exist. Tighten the anchoring screws, controlling the torque to 0.8 N m, to avoid damage to the probe.

Standard Data Acquisition: Use the calibration probe of the high-precision temperature monitoring instrument against the corresponding flow channel temperature measurement point of the sensor to be calibrated and temporarily affix it with high temperature resistant tape to ensure full contact between the probe and the flow channel surface.

The system is then switched on again and maintained warm for 30 min, after which synchronous data collecting is started. Record 10 sets of data, including the temperature displayed by the temperature controller and the actual temperature detected by the standard monitoring device, every minute.

Calculation of deviation and parameter correction Average deviation = Average temperature displayed by the temperature controller - Average temperature measured by the standard monitoring instrument = Average deviation of 10 sets of data.

Access the sensor calibration menu of the Husky temperature control system, locate the cold junction compensation correction parameter of the corresponding channel, and input the calculated average deviation into the offset compensation item of the temperature controller to realize manual correction of the parameter.

Calibration Effect Verification Perform parameter correction, continue to run for 1 hour at high temperature, synchronously acquire 5 groups of temperature data to verify that the temperature measurement error of the sensor is stably regulated within ±1℃.

Manually start and stop the heater 3 times, observe the PID adjustment process, check the temperature overshoot is <=2 degree Celsius, the temperature back to the set value in 3 minutes and no jumps and drifts.

III. Post-calibration Completion and Archiving

Clean the residual thermal grease on the surface of the flow channel and restore the equipment to the normal production status. Remove the probe of the standard inspection instrument.

As benchmark reference data for further periodic inspections, record in the hot runner sensor calibration logbook the channel number, original deviation, correction parameters and verification data of this calibration.

Conduct a small-lot trial production of 20 molds to check that no defective products are generated from aberrant temperatures (e.g., flash, lack of glue), and ensure process stability is fully up to specification after calibration.