Case 1: Recurring thermocouple breakage alarms caused by improper soldering.
Background: A Husky hot runner thermostat at an automobile parts injection moulding machine was triggering thermocouple breaking alarms every 2-3 hours after being reset. Despite multiple thermocouple replacements, the problem persisted.
Long-term high-temperature oxidation of the thermocouple terminals resulted in inadequate soldering that caused inconsistent continuity. The thermostat occasionally read a normal signal, and following a reset, it worked normally for a brief period of time. However, vibration or temperature fluctuations led the faulty soldering to fail, quickly setting off the alert.
Complete Solution: All terminal oxide layers were re-ground, and high-temperature resistant crimp-type terminals were installed, eliminating the possibility of faulty soldering. The channel then worked consistently for 18 months without experiencing any such alarms.
Case 2: Ground loop interference causes repeated false triggers of over-temperature alarms.
Background: A Husky temperature controller on a medical consumables injection moulding production line was triggering random over-temperature alarms 3-5 times per day after being reset, despite the fact that the actual hot runner temperature was entirely normal with no signs of overheating.
Root cause: A freshly installed servo motor on the production line was not correctly grounded, resulting in a grounding loop. This resulted in an anomalous interference voltage in the thermocouple signal circuit, causing the temperature controller to sample false high-temperature data and incorrectly activate the overheating warning.
Complete Solution: By re-standardizing the hot runner system's single-point grounding and adding a signal isolator in the thermocouple signal circuit to block the interference path, the alarm recurrence problem was completely eradicated.
Case 3: A partial short circuit in the heating coil results in repeated overload alarms.
Background: When the temperature reached to roughly 180°C in a daily requirements injection moulding facility, an overload alert reoccurred after being reset. After cooling and resetting, it was able to briefly resume regular operations.
The insulation layer of the heating coil in the hot runner has aged due to sustained high temperatures, which is the root cause of the defect. Heating causes a sharp drop in insulation resistance, resulting in a partial short circuit and activating the thermostat's overload protection alarm. After cooling, the insulating resistance returns to normal, and the gadget can be briefly used after resetting.
Complete solution: Replace the ageing heating coil and re-match the thermostat's output current protection threshold. Afterward, the temperature control performance of this channel is entirely steady, and the alarm does not reoccur.
These three situations cover more than 90% of the field scenarios in which Husky thermostat alerts reappear after resetting, and they can be used as a straight reference for addressing similar issues.
