Thermocouple failures are one of the main causes of hot runner system downtime, and common problems have obvious characteristics and causes. The most frequent failure is open circuit, mainly due to internal alloy wire breakage caused by thermal cycling fatigue, mechanical vibration, or improper installation and bending. Frequent temperature changes cause repeated expansion and contraction of the wire, which eventually leads to fracture, especially for low-quality thermocouples.
Short circuit is another common problem, usually caused by damage to the internal insulation layer. Molten plastic infiltration, moisture erosion, or chemical corrosion will damage the magnesium oxide insulation, causing the two alloy wires to contact and generate signal interference. Temperature drift is also widespread, resulting from impure alloy materials, high-temperature aging, or long-term use, leading to inaccurate temperature measurement and affecting molding quality.
Mechanical damage, such as crushed probes, worn cables, or loose connectors, will cause intermittent signal interruption and unstable temperature. In addition, electromagnetic interference from unshielded wires or unreasonable wiring will distort the thermocouple signal, resulting in temperature fluctuations. Many problems can be avoided by selecting high-quality products, standardizing installation, and regular maintenance. Understanding these common problems helps users quickly diagnose faults and reduce production losses.
