During injection molding process, stability and reliability of hot runner system are crucial to ensuring product quality and production efficiency. However, due to influence of various factors, various abnormal phenomena may occur in hot runner system. This article will analyze in detail common abnormal phenomena, causes and solutions of hot runner system.

Phenomenon description: Hot runner system cannot heat up to set temperature, resulting in inability of injection molding to proceed normally.
Cause analysis:
Heating wire broken: Due to long-term high-temperature operation or improper use, heating wire may break, resulting in inability to transfer heat.
Poor contact of connecting wire or connecting system (socket): Connecting wire is loose or socket pins are deformed, resulting in inability to transmit current stably.
Poor temperature control box: Internal components of temperature control box are damaged or aged, resulting in failure of temperature control.
Reverse polarity of temperature sensing line: Reverse polarity of temperature sensing line will cause temperature signal transmission error, affecting judgment of temperature control box.
Temperature sensing line broken: Temperature sensing line broken will cause temperature signal to be unable to be transmitted to temperature control box.
Open hot runner system (integrated)

 

Solution: Use a multimeter to check integrity of heating wire and temperature sensing line, and replace it in time if it is broken. Check whether all connecting wires and socket pins are loose or deformed to ensure reliable connection. Check whether hot runner temperature sensing line and temperature control box setting model match to ensure normal operation of temperature control box. Check whether polarity of temperature sensing line is connected correctly to avoid abnormal temperature control caused by reverse polarity. Use a multimeter to check whether fuse and thyristor are damaged, and replace damaged components in time. If temperature control box does not display, consider replacing a new temperature control card.

Phenomenon description: Leakage occurs in hot runner system during injection molding process, affecting product quality and production efficiency.
Cause analysis:
Poor mold assembly: Inaccurate mold processing dimensions or improper assembly, resulting in hot runner system cannot fit tightly.
Poor assembly of hot runner system itself: Internal parts of hot runner system have incorrect dimensions or assembly sequence is improper.
Injection molding machine nozzle and main nozzle of manifold do not match: Matching dimensions of injection molding machine nozzle and main runner of hot runner do not match.
Matching tolerance of valve needle and valve needle guide sleeve is too large: Gap between valve needle and guide sleeve is too large, resulting in material leakage.
Poor sealing: Nozzle and mold sealing part do not fit well, resulting in molten material leakage.
Cracks in nozzle and valve needle guide sleeve: Long-term high-temperature operation or improper use causes cracks in nozzle and valve needle guide sleeve.
Solution: Confirm processing dimensions of mold to ensure assembly accuracy of mold. Disassemble hot runner system, confirm that dimensions of each part are correct, and assemble them in correct assembly sequence. Make sure that "R" of injection molding machine nozzle is smaller than "R" of main runner to achieve a tight fit. Replace new valve needle and valve needle guide sleeve to ensure that matching tolerance is reasonable. Check matching of nozzle and mold sealant, and repair poor matching parts in time. Replace new nozzle and valve needle guide sleeve to avoid leakage caused by cracking.

Phenomenon description: After hot runner system is shut down for a long time or during injection molding process, molten material carbonizes inside hot runner, affecting product quality and production efficiency.
Cause analysis:
Hot runner system temperature is not reduced during long-term shutdown: During long-term shutdown, hot runner system temperature is not reduced to a safe range, resulting in carbonization of molten material at high temperature.
Carbonization near gate: Molten material near gate stays for too long, resulting in carbonization.
Material stagnation inside injection molding machine nozzle or manifold: Molten material remains inside injection molding machine nozzle or manifold, and carbonization occurs under long-term high temperature.
Material stagnation inside hot nozzle: Molten material remains inside hot nozzle, and carbonization occurs under long-term high temperature.
Improper fixing state and connection method of temperature sensing line: Temperature sensing line is not fixed firmly or connection method is improper, resulting in inaccurate temperature control and carbonization.
Temperature control box temperature control card, thyristor is bad: Internal components of temperature control box are damaged or aged, resulting in unstable temperature control and carbonization.
Solution: When machine is shut down for a long time, reduce temperature of hot runner system to a safe range to avoid carbonization of molten material at high temperature. Check and clean carbides near gate to ensure smooth flow of molten material. Clean stagnant material inside injection molding machine nozzle and manifold to avoid carbonization at high temperature for a long time. Clean stagnant material inside hot nozzle to ensure smooth flow of molten material inside hot nozzle. Check fixing state and connection method of temperature sensing line to ensure accurate temperature control. Check whether internal components of temperature control box are damaged or aged, and replace damaged components in time to ensure stable temperature control.
In summary, for common abnormal phenomena of hot runner system, we need to analyze faults and formulate solutions from multiple aspects. By strengthening daily maintenance, regular inspections and timely replacement of damaged components, we can ensure stability and reliability of hot runner system, improve product quality and production efficiency of injection molding.