What Common Operation Faults Occur In Daily Hot Runner Use?

A number of common equipment faults can easily arise in the long-term continuous production and use process of hot runner systems, which are influenced by factors such as raw material characteristics, mold working environment, operation specification, accessory aging, and installation errors. The majority of these faults are closely related to the failure, inaccurate detection, poor contact, and signal abnormality of core temperature sensing accessories represented by hot runner thermocouples. Understanding frequent hot runner defects, fault manifestation features, and root causes can assist production maintenance staff in promptly identifying issues, promptly removing hidden hazards, cutting down on shutdown maintenance time, and preventing the mass production of faulty plastic items.

The most common issue with hot runners in everyday use is temperature abnormal fluctuation faults, which include inability to reach the desired heating temperature, slow heating speed, abrupt display temperature jump, unstable temperature floating up and down, and inconsistent temperature of each partition. Thermocouple failure issues are the primary cause of these faults: loose thermocouple installation results in poor contact with heating components, which causes delayed temperature sensing and low detected temperature; long-term high-temperature use causes aging wire core and signal transmission distortion of thermocouples, which causes a sudden jump in display temperature; thermocouple high-temperature oxidation and internal circuit breakage result in no temperature signal feedback, and the temperature controller displays abnormal numerical values. Temperature irregularities can also be caused by heating pipe burnout, wire harness virtual connections, and inadequate heat insulation, however the majority of temperature fluctuation issues are primarily caused by thermocouple failure.

The assembly gap between the manifold and nozzle as well as the location of the hot runner's connection to the mold cavity are common locations for hot runner internal material leakage faults. Melt overflow at the gap, material adhering to the hot runner surface, and challenging mold opening after cooling are the primary symptoms. The primary causes are excessive installation fastening force, aging and corrosion of high-temperature resistant sealing gaskets, excessive injection pressure setting, and an unacceptable thermal expansion reserved gap in the hot runner structural design. In the meantime, excessive local heating and accelerated aging of sealing accessories are caused by long-term temperature deviation measured by imprecise thermocouples, which indirectly increases the likelihood of material leakage problems.

Hot runner temperature failure-related product molding appearance flaws, such as nozzle wire drawing, material leaking, product surface burn marks, carbon deposition black spots, filling shortage, uneven product weight, and visible gate traces, are also very common in production. The primary reason of nozzle wire drawing and material dripping is an excessively high nozzle tip temperature, which results from the controller setting an excessive heating temperature since nozzle thermocouples are unable to reliably measure actual temperature. Local overheating of hot runner runners results in product surface burn scars and carbon deposition, while thermocouples' temperature monitoring blind region causes raw materials to be retained at high temperatures for extended periods of time, as well as thermal degradation and carbonization. Overall low hot runner temperature and poor melt fluidity, which results from erroneous thermocouple overall temperature detection and irrational temperature regulation, are the causes of filling scarcity and uneven filling.

Furthermore, frequent burnout of heating elements, temperature controller signal failure, hot runner valve needle jamming, and other mechanical and electrical issues frequently arise in actual production. The unstable operation brought on by long-term temperature data variation is the source of the majority of these issues. In order to significantly increase fault maintenance efficiency, promptly restore normal production order, and successfully lower the defective rate of injection molding products caused by hot runner faults, maintenance personnel should first check the working state of each group of hot runner thermocouples, calibrate temperature detection accuracy, eliminate temperature sensing failure hidden dangers, and then check mechanical structure and circuit faults.