How to Clean the Cooling System of a Hot Runner Multi-Cavity Mold

Cleaning the cooling system of a hot runner multi-cavity mold requires a combination of physical pulse cleaning, chemical descaling, and regular maintenance to ensure unobstructed water flow and efficient heat exchange, preventing uneven cooling, mold deformation, or machine shutdown due to scaling or blockage.

1. Preparation and Safe Shutdown Before Cleaning

Turn off the power to the equipment and the cooling system. Stop the injection molding machine and disconnect the power to the mold temperature controller and water pump to prevent misoperation.

Drain the cooling water. Open the drain valve to completely drain any residual water from the system, preventing dilution of the cleaning solution or cross-contamination.

Disconnect the mold inlet and outlet water connectors. Use a special tool to disassemble the quick-connect fittings, taking care to protect the O-rings and threaded interfaces.

2. Recommended Cleaning Methods and Operating Procedures

(1) Physical Pulse Cleaning (Preferred Method)

Suitable for removing deposits such as scale, rust, and biofilm, it can efficiently clean without disassembling the mold. Equipment: Mold water circuit cleaning machine (with pulse generator)

Media: Clean water or circulating liquid with added special cleaning agent

Operating procedure:

Connect the outlet of the cleaning machine to the inlet of the mold, and the return outlet to the outlet.

Set the pulse frequency (recommended 80-120 times/minute), pressure 0.5-0.8MPa.

Start the equipment, clean each circuit for 5-10 minutes until the effluent is clear.

Backwash once to ensure that impurities in dead corners are flushed out.

Advantages: Does not damage pipe walls, can handle curved and narrow water circuits, high efficiency.

(2) Chemical cleaning (suitable for stubborn scale)

For calcium and magnesium deposits and iron oxide rust layers caused by long-term use of hard water, chemical agents are needed to soften and decompose them. Agent Selection: Mild scaling: Weak acid descaling agent (e.g., citric acid solution) Severe scaling: Special mold waterway descaling agent (e.g., Ryton, Mold-Clean series)

Operating Procedure:

Prepare the solution according to the ratio (usually 1:10 to 1:20)

Soak statically for 2-4 hours, or continuously clean with a circulating pump for 1 hour

Drain the solution and rinse repeatedly with clean water until the pH is neutral

Check if the effluent is clear and free of suspended matter

Note: Avoid using strong acids to prevent corrosion of the mold steel; after cleaning, it must be thoroughly neutralized and rinsed clean.

(3) Endoscopic Inspection and Local Treatment

For areas difficult to clean, such as slender cores and deep-hole waterways, an endoscope can be used to check for blockages, and high-pressure nozzles can be used for directional flushing.

3. Post-Cleaning Inspection and System Restoration

Water Flow Test

Reconnect the connectors and flow water to observe whether the flow rate returns to normal and whether there are any leaks. **Pressure Test:** Maintain pressure at 1.5 times the working pressure for 10 minutes to confirm no leakage.

Mold Temperature Controller Calibration: Calibrate the temperature sensor after restarting to ensure temperature control accuracy ≤ ±0.5℃.

Maintenance Record: Record cleaning time, method, chemicals, any abnormalities found, and their handling results for future traceability.

4. Recommended Cleaning Cycle:

Case Study: A Wuhan auto parts factory achieved a 65% reduction in cooling system failure rate and a nearly 40% increase in mold life through quarterly pulse cleaning.