Mold Water Leak Detection and Maintenance
Injection mold cooling systems directly affect product quality, production stability, and mold service life. Water leakage is one of the most common failures in injection molding. Minor leaks cause poor cooling, dimensional deviation, and surface defects on molded parts. Severe leaks lead to electrical hazards, mold rust, template cracking, and extended downtime. Effective leak management requires accurate positioning, targeted repairs, and standardized prevention to ensure long-term stable production.
1. Leak Detection Methods
Visual inspection is the most basic method. After shutting down the machine, dry all connectors, plugs, parting lines, and insert joints. Run cooling water under normal pressure of 0.4–0.6 MPa and hold for 15–20 minutes to observe obvious water seepage. This method quickly locates external leaks but fails to identify internal cracks and micro-leakage.
The soapy water pressure test is widely used in workshops. Seal the water circuit, inject 0.3–0.4 MPa compressed air, and apply soapy water to suspected areas. Continuous bubbles indicate leakage points. This method is low-cost and efficient for hidden leaks around inserts, baffles, and threaded holes.
Water pressure holding testing verifies overall sealing performance. Pressurize the system to 0.4–0.6 MPa and maintain for 30 minutes. A pressure drop greater than 0.05 MPa confirms internal leakage. For ultra-fine micro-leaks, fluorescent tracer detection is recommended. By adding fluorescent agent and using ultraviolet lamps, tiny leakage paths can be clearly identified. Thermal imaging can also scan temperature differences during production to locate low-temperature leakage zones without halting production.
2. Repair Strategies for Common Leak Points
Leaks at quick connectors and pipe joints are usually caused by damaged O-rings, loose nuts, or worn threads. Maintenance includes replacing high-temperature fluororubber seals, cleaning thread surfaces, applying thread sealant, and tightening with a torque wrench to avoid over-tightening cracks.
Plugs and threaded holes often leak due to damaged threads, degraded sealant, or improper installation. The repair process involves removing old seals, cleaning holes, re-applying PTFE tape and anaerobic adhesive, and reinstalling plugs with appropriate torque. For damaged threads, re-tapping or insert repair is required.
Leaks at insert fitting surfaces and core/cavity gaps mainly result from excessive clearance, worn seal grooves, or micro-cracks. Solutions include adding custom sealing rings, installing PTFE gaskets, reprocessing seal grooves, or performing argon arc welding for cracks. After repair, the mold must be polished and re-tested.
Parting surface leakage is often caused by damage, material build-up, or template deformation. Technicians should clean residual plastic, repair dents, grind the parting surface, and check flatness. For structural cracks in templates, low-temperature welding or inlay repair is used to prevent further deformation.
Baffle leakage causes water short-circuiting and uneven cooling. Faulty baffles must be replaced or re-fixed with sealing gaskets to ensure independent water inlet and outlet circuits.
3. Post-Repair Verification and Prevention
All repaired molds must pass a pressure test of 0.4–0.6 MPa for at least 30 minutes with no pressure loss or seepage. Key molds require testing at 1.5 times working pressure. Routine maintenance should include regular cleaning of water scales, inspection of seals, and replacement of aging parts every 3–6 months.
Using high-temperature resistant seals, optimizing water channel design, and avoiding overpressure can significantly reduce leakage. Standardized operation and gentle mold handling also prevent mechanical damage that leads to water leakage.
