What are the steps for manually calibrating a hot runner sensor?

I. Preparatory Steps Prior to Calibration:

1. Check that the hot runner heater cannot leak current, that the insulation resistance of all channels is ≥5MΩ, and that there is no static/dynamic leakage danger.

2. Heat the hot runner to the rated operating temperature of 320℃, and keep the temperature of the hot runner at this temperature for 2 hours, so that the overall temperature of the hot runner reaches a stable functioning state. There is no overcurrent alarm and temperature jump alarm from the temperature controller.

3. Prepare the whole set of equipment in advance, including the CNAS calibrated high-precision temperature monitoring instrument, 500V digital megohmmeter, 350℃ heat-resistant insulated gloves, high-temperature thermal lubricant and compact screwdriver with torque display.

 

II. Pre-treatment and Installation Procedures for Probe:

1. Put on heat resistant insulated gloves. Turn off and disconnect power. Gently withdraw the thermocouple probe to be calibrated out of the temperature sensor hole of the hot runner. Clean the surface of the probe of remaining old thermal grease.

2. Apply a thin and uniform amount of high temperature thermal grease to the temperature sensing end of the probe. Re-insert the probe into the bottom of the temperature detecting hole. The probe shall be in full contact with the metal body of the runner with no gaps.

To avoid damage to the thermocouple probe by excessive torque, tighten the probe mounting screws at 0.8 N·m using a screwdriver with torque indication.

 

III. Acquisition steps of reference data Fix the calibration probe of the high-precision temperature monitoring instrument firmly on the flow channel temperature measurement point corresponding to the sensor to be calibrated, and temporarily fix it with high-temperature resistant polyimide tape to ensure the probe is in full contact with the flow channel surface.

Turn the system back on and keep the heat on for 30 minutes so that the temperature measurement data from the two probes are fully synced and steady.

– Every minute, register a set of temperature measurements of the temperature controller and standard monitoring device, continuously obtaining 10 sets of valid data to prevent the calibration accuracy from being affected by single sampling errors.

 

IV. Deviation calculation and parameter correction steps: Determine the mean temperature readings of the temperature controller and the average temperature readings of the standard monitoring equipment for 10 groups of data, and get the average deviation between the two.

Then, enter the sensor calibration menu of the Husky temperature control system, find the cold junction compensation correction parameter item of the corresponding channel, enter the average deviation calculated in the offset compensation column of the temperature controller, and complete the manual parameter correction.

Save the parameter values and exit the calibration menu. Confirm that there is no aberrant alert in the temperature controller due to the modification of parameters.

 

V. Verification of Calibration Steps Effectiveness

After correcting the parameters, run at high temperature for 1 hour, and then collect 5 sets of temperature data synchronously again to verify that the temperature measurement error of the sensor is stably controlled within ±1℃.

Manually switch the heater on and off 3 times, examine the PID adjustment process, and check that the temperature overshoot is ≤2℃, returns to the set value within 3 minutes, and there are no temperature jumps and baseline drift.

Remove the standard inspection instrument probe, clean the residual thermal grease on the surface of the flow channel, and restore the normal wiring condition of the equipment.

 

VI. Final Archival Process

This calibration shall be completely recorded in the hot runner sensor calibration logbook, including the channel number, initial deviance, corrected parameters and verification data as benchmark reference data for further periodic inspections.

Do a small batch trial production of 20 mold goods to validate that there are no defective products produced by anomalous temperature such as flash or insufficient glue, and verify that the process stability after calibration is fully up to the standard.