What Causes Intermittent Signal Failure Of Hot Runner Thermocouples

One of the most problematic hidden issues with hot runner thermocouples is intermittent signal failure. In daily inspection, it might be challenging to identify and troubleshoot when the temperature display abruptly jumps or sounds an alarm without any regulations. If this type of intermittent problem is not resolved in a timely manner, it will result in long-term temperature control disorder and batch quality fluctuation. It is caused by hidden structural deterioration, poor contact, wiring fatigue, and environmental degradation.

Internal wire concealed fractures and virtual connections between welding joints are the primary causes. The thermocouple lead is repeatedly bent and pulled during the opening and closing of the mould. The internal alloy wire will partially shatter due to prolonged fatigue. Intermittent signal interruption results from the circuit being connected while it is static and disconnected when it is vibrating or moved. Split-assembled thermocouples are more likely to have virtual welding at the probe-lead connection, which will loosen as a result of thermal expansion and contraction at high temperatures, creating an unstable contact.

Oxidation corrosion and inadequate terminal contact are the second cause. Long-term exposure to high-temperature gas, oil mist, and workshop humidity affects the temperature controller's wiring terminal. As a result, the metal contact piece oxidises and rusts, increasing contact resistance. The display temperature jumps irregularly due to the sporadic transmission of the temperature signal. Poor contact under equipment vibration can also be caused by ageing terminal shrapnel and loose wiring screws.

Probe installation gaps and carbon deposition pollution make up the third factor. An isolation layer formed by thick carbon deposition and oil filth on the probe surface causes the temperature response to lag and the signal to become unstable; an excessively large installation gap causes unstable heat conduction and variable temperature feedback. Furthermore, in a humid environment, a broken insulation layer results in weak short circuits and occasional leaks, which also create erratic temperature displays.

Intermittent signal failures can be fully resolved by promptly troubleshooting concealed fractures, cleaning oxidised terminals, standardising wiring fixing, and routinely clearing probe carbon buildup. Such concealed issues can be completely avoided by replacing integrated sealed anti-fatigue thermocouples, which will preserve the hot runner temperature control system's long-term stable performance.