Troubleshooting Methods for Thermocouple Temperature Display Floating Fault

Temperature display floating is a frequent non-stable abnormal event in the day-to-day functioning of hot runner systems. Its primary symptom is that, without changing any process parameters, the displayed temperature value varies erratically up and down within a specific range. This significantly disrupts the regular consistent temperature management and has an impact on the stability of injection molding production. Using standardized inspection techniques, it is essential to precisely identify fault points and gradually remove concealed hazards.

Poor contact and virtual connections at wire locations are the first common cause of faults. The terminal fastening screws inside the temperature control box may eventually become loose due to prolonged equipment vibration, which will cause the wire core and terminal sheet to make poor contact. Furthermore, oxidation rust and dust buildup at the wire contact points will raise contact resistance, leading the signal transmission state to become unstable and temperature data to continuously float. The fix is to turn off the power for a safety check, disassemble each wiring terminal individually, clean and remove oxide rust from the contact surface, tighten any loose screws, and make sure the wiring is gap-free and tight.

The thermocouple's unstable installation status is the second reason. There will be spaces between the probe and the mounting hole if the thread is not securely secured after installation. The contact state between the probe and the heated matrix is constantly changing due to the alternating effect of high-temperature thermal expansion and mold vibration, which causes unstable heat conduction efficiency and varying measured temperature. Re-adjusting the thermocouple's insertion depth, cleaning sundries inside the mounting hole, tightening the thread to guaranty a snug fit, and routinely inspecting the fastening condition to avoid displacement and loosening are all tasks that maintenance staff must perform.

Thirdly, another significant causative factor is external electromagnetic interference. Strong alternating magnetic fields will interfere with weak thermoelectric signals when thermocouple signal wires are placed next to high-voltage power lines or when high-power frequency converters, servo motors, and other equipment are operating nearby. This will cause distorted feedback data and noticeable temperature floating. To improve signal anti-interference capabilities, the wiring paths should be rearranged, strong current and weak current lines should be laid separately, high-quality insulated compensation wires should be used, and standard single-point grounding should be used.

Fourth, this issue will also be caused by partial thermocouple damage and aging internal performance. After extended usage, the measuring head's welding points have loose, hidden cracks, and the internal wire cores have localized fatigue damage. The output signal is constantly fluctuating at random, and the thermoelectric conversion status is unstable. These old and broken thermocouples can only be replaced with new, approved items in time to fully resolve the floating issue; they cannot be fixed with straightforward maintenance and adjustment.

Subtle temperature variations and data floating will also result from excessive local air flow and unstable heat dissipation surrounding the hot runner. Once all external interference and mechanical hidden issues have been removed, do a low-temperature trial heating observation to ensure that the temperature display is stable and normal before formally starting production again. Melt fluidity can be stabilized, accurate consistent temperature control can be restored, and various quality flaws brought on by unstable temperature may be successfully avoided by promptly eliminating temperature floating faults.