Hot Runner Nozzle Leakage: Causes and Solutions
Hot runner nozzle leakage is one of the most frequent failures in precision injection molding. It causes material waste, product defects, component damage, and unplanned downtime. This article explains the main causes, on-site handling steps, targeted repair methods, and preventive measures to quickly resolve leakage and ensure stable production.
Common Causes of Leakage
Leakage usually results from damaged sealing surfaces, poor alignment between nozzle and gate, unstable temperature settings, excessive injection pressure, or worn components such as nozzles, seals, and heating parts. These issues create small gaps where molten plastic can escape under high pressure.
Immediate On-Site Handling
When leakage occurs, stop production and reduce pressure immediately to prevent further carbonization and damage. Lower the nozzle temperature safely and identify the leakage position. Allow the system to cool fully before disassembly to avoid thread seizure or surface scratches. Use copper tools to clean resin and carbon deposits without damaging sealing surfaces.
Repair by Leakage Location
Leakage at Nozzle Tip
Check the nozzle contact surface for dents, scratches, or deformation. Lightly polish minor damage; replace severely worn nozzles. Clean the gate bushing thoroughly and ensure full, flat contact. Correct alignment between nozzle and mold to eliminate side gaps. Slightly lower nozzle temperature to increase melt viscosity and reduce seepage.
Leakage at Nozzle Base
Inspect seals and gaskets for aging or damage and replace them with high-temperature resistant parts. Tighten the nozzle evenly to avoid distortion. Check the manifold contact surface for flatness and polish if needed to restore effective sealing.
Leakage Under High Pressure
Reduce injection speed, pressure, and holding time to avoid overloading the seal. Adjust the V‑P switch point to lower pressure buildup in the hot runner. Stabilize temperature to prevent local overheating and excessive flowability.
Long-Term Wear Leakage
Replace worn nozzle tips, nozzles, or sealing components. Check heating coils and sensors for failure, as uneven temperature accelerates wear and leakage.
Post-Repair Commissioning
Heat gradually and hold temperature to ensure uniform thermal expansion. Run low‑pressure, low‑speed test shots to confirm no leakage. After confirming stability, restore standard parameters and monitor for 3–5 cycles before full production.
Preventive Measures
Ensure accurate alignment and clean sealing surfaces during installation. Use stable temperature and pressure within design limits. Perform monthly maintenance: check seals, heaters, sensors, and nozzle condition. Match nozzle type to plastic material, especially for abrasive or high-temperature resins.
Conclusion
Hot runner nozzle leakage is mainly caused by poor sealing, misalignment, temperature error, overpressure, or wear. Effective handling includes locating the leak, cleaning components, targeted repair, low‑pressure testing, and preventive maintenance. Proper procedures minimize downtime, reduce waste, and maintain consistent, reliable injection molding performance.
