What are the common faults of hot runner systems?

Common faults of hot runner systems are as follows:
Temperature control failure
Temperature is too high: It may be a thermostat failure, such as damage to internal electronic components, resulting in abnormal control of the heating element, causing the temperature to continue to rise. A short circuit in the heating element can also cause this situation, such as damage to the insulation layer of the heating rod, abnormal increase in current, and excessive heat generation. In addition, improper installation of the thermocouple, which cannot accurately measure the actual temperature, can also cause the thermostat to misjudge, and continuous heating will cause the temperature to be too high.
Temperature is too low: The reason may be aging or damage to the heating element, such as the resistance of the heating coil increases and the heating power decreases after long-term use. Thermocouple failures, such as line disconnection and poor contact, will prevent the thermostat from receiving accurate temperature signals, thereby erroneously reducing the heating output. In addition, power supply system failures, such as unstable voltage and phase-loss power supply, can also lead to insufficient heating power and cause low temperatures.
Plastic melt flow failure
Runner blockage: It is usually caused by impurities and foreign matter in the plastic particles entering the hot runner, or the plastic stays in the runner for a long time, carbonizing and agglomerating, which hinders the normal flow of the melt. In addition, unreasonable flow channel design, dead corners or narrow parts, can also easily cause material accumulation and blockage.
Melt leakage: Aging and damage of seals are common causes of melt leakage, such as the loss of elasticity and cracks of the sealing ring, which cannot be effectively sealed. Improper installation of components of the hot runner system, such as uneven tightening force of bolts, resulting in gaps between components, can also cause melt leakage. In addition, cracks in the flow channel due to long-term heat and pressure can also cause melt leakage.
Uneven flow rate: This may be due to uneven temperatures in various heating areas of the hot runner system, resulting in inconsistent viscosity of the plastic melt, thus affecting the flow rate. Unreasonable flow channel layout, such as large differences in the length and diameter of each branch flow channel, can also cause different flow rates of the melt in different flow channels. In addition, improper hot nozzle design, such as inconsistent nozzle size and irregular flow channel shape, can also cause uneven flow rate.
Hot nozzle failure
Hot nozzle blockage: It may be due to impurities in the plastic melt, cold material head, etc. blocking the hot nozzle nozzle. The needle valve in the hot nozzle is not flexible and cannot be fully opened, which will also cause poor material flow and blockage.
Hot nozzle leakage: The sealing surface of the hot nozzle is damaged, such as long-term contact with the mold, or scratched by foreign objects, which will reduce the sealing performance and cause leakage. The gap between the needle valve of the needle valve hot nozzle and the hot nozzle body is too large, or the seal of the needle valve is damaged, which will also cause leakage.
Abnormal hot nozzle temperature: Failure of the heating element of the hot nozzle, such as burning of the heating wire, will cause the temperature of the hot nozzle to be too low. The poor insulation effect of the hot nozzle, the heat dissipation to the surrounding environment, or the inaccurate temperature control of the hot nozzle by the thermostat may cause the temperature of the hot nozzle to be too high.
If the hot runner system fails, it will directly affect the quality and production efficiency of plastic products, so timely diagnosis and maintenance are required.