Intermittent signal failure is one of the most troublesome hidden faults of hot runner thermocouples. The temperature display is normal occasionally, and suddenly jumps or alarms without rules, which is difficult to detect and troubleshoot in daily inspection. This kind of intermittent fault is not sudden damage, but is caused by hidden structural damage, poor contact, wiring fatigue and environmental erosion, which will lead to long-term temperature control disorder and batch quality fluctuation if not solved in time.
The first major cause is internal wire hidden fracture and welding joint virtual connection. During mold opening and closing, the thermocouple lead is repeatedly bent and pulled. Long-term fatigue will cause partial fracture of the internal alloy wire. The circuit is connected when static, and disconnected when vibrating or displaced, resulting in intermittent signal interruption. Split assembled thermocouples are more prone to virtual welding at the connection between probe and lead, which will loosen due to high-temperature thermal expansion and contraction, forming unstable contact.
The second reason is poor terminal contact and oxidation corrosion. The wiring terminal of the temperature controller is affected by workshop humidity, oil mist and high-temperature gas for a long time, and the metal contact piece is oxidized and rusted, resulting in increased contact resistance. The temperature signal is transmitted intermittently, showing irregular jumping of display temperature. Loose wiring screws and aging terminal shrapnel will also cause poor contact under equipment vibration.
The third factor is probe installation gap and carbon deposition pollution. Too large installation gap leads to unstable heat conduction and fluctuating temperature feedback; thick carbon deposition and oil dirt on the probe surface form an isolation layer, making the temperature response lag and signal unstable. In addition, damaged insulation layer causes intermittent leakage and weak short circuit under humid environment, which also induces irregular temperature display abnormality.
Timely troubleshooting hidden fracture, cleaning oxidized terminals, standardizing wiring fixation and regularly cleaning probe carbon deposition can completely solve intermittent signal faults. Replacing integrated sealed anti-fatigue thermocouples can fundamentally avoid such hidden troubles and maintain the long-term stable operation of hot runner temperature control system.
