Thermocouple calibration is the process of verifying and adjusting a sensor's output to ensure it accurately measures temperature. Over time, all thermocouples drift due to thermal cycling, mechanical stress, and contamination. In hot runner systems, this drift can lead to costly consequences: inconsistent part quality, material waste, and machine downtime. Therefore, regular calibration is not just maintenance but a quality control necessity.
The calibration process involves exposing the thermocouple to known temperature points, typically using a dry-block calibrator or a reference thermometer. The controller then compares the thermocouple's reading to the reference value and makes adjustments. For hot runners, this must be done at the operating temperature, as cold calibration can lead to inaccuracies when the system is hot. Multi-zone systems require each thermocouple-nozzle and manifold-to be calibrated individually.
Many automotive and medical molders perform quarterly or semi-annual calibrations to meet ISO and TS standards. Poor calibration can result in temperature errors exceeding 5-10°C, causing burn marks, flow lines, or dimensional instability. Investing in a robust calibration program not only ensures compliance but also extends the lifespan of heaters and nozzles by preventing overheating.
