The hydraulic system is the core power source of the injection molding machine, and its stability directly affects the life of the equipment and product quality. However, hydraulic oil contamination is one of the main causes of system failures (such as valve core stuck, pump wear, and unstable pressure). According to statistics, about 70% of hydraulic system failures are caused by oil contamination. This article will introduce 5 key maintenance steps to help you effectively prevent pollution and extend the service life of the hydraulic system of the injection molding machine.
The main sources and hazards of hydraulic oil contamination
1. Types of pollutants
Solid particles: metal chips, dust, seal debris (main hazards: scratching the cylinder barrel, blocking the valve core).
Moisture: condensed water or external infiltration (causing oil emulsification and rusting metal parts).
Air: mixed with oil to form bubbles (causing cavitation and pressure fluctuations).
Chemical pollutants: colloid and sludge produced by oil oxidation and deterioration.
Typical failures caused by pollution
Unstable system pressure → dimensional deviation of injection molded products.
Abnormal noise from hydraulic pump → wear of bearing or valve plate.
Solenoid valve stuck → delayed action or failure.
2. 5 key steps to avoid hydraulic system contamination
Step 1: Regularly inspect and replace hydraulic oil
✅ Inspection frequency: Sampling and inspection every 3 months (focus on monitoring particle count, moisture content, and acid value).
✅ Replacement standard:
Particle contamination level exceeds ISO 4406 18/16/13 (NAS 1638 level 9).
Moisture content > 0.1% (or oil is turbid and emulsified).
✅ Oil change operation:
After draining the old oil, flush the system with new oil of the same model.
It is recommended to use anti-wear hydraulic oil (such as HM46) and ensure that the viscosity matches the equipment requirements.
Step 2: Install a high-precision filtration system
✅ Filter selection:
Oil suction port: 100~150μm filter (to prevent large particles from entering the pump).
Pressure line: 10μm high-pressure filter with β≥200 (to protect precision valves).
✅ Maintenance points:
Check the filter pressure difference every month, and replace the filter element if it exceeds 0.3MPa.
Install an air dryer on the oil tank breathing valve to prevent dust and moisture from invading.
Step 3: Sealing and dust prevention management
✅ Key sealing point inspection:
Cylinder piston rod: Use a dust ring + step seal combination to regularly clean impurities on the rod surface.
Fuel tank cap: Ensure that the seal is intact and avoid open refueling.
✅ Dust prevention measures:
Install a dust cover around the hydraulic station of the injection molding machine, especially in dusty workshops.
Step 4: Control oil temperature and moisture
✅ Oil temperature management:
Maintain the oil temperature at 40~60℃ (exceeding 65℃ accelerates oil oxidation).
Install an oil cooler or radiator to avoid high-temperature operation.
✅ Waterproof measures:
Set a drain valve at the bottom of the oil tank to discharge condensed water regularly.
Use a vacuum dehydrator (for high humidity environments).
Step 5: Standardize maintenance and operation procedures
✅ Daily maintenance:
Use a special filter cart (filtration accuracy ≤ 5μm) when refueling.
Clean the pipeline thoroughly after maintenance to avoid impurities.
✅ Operation training:
It is forbidden to directly replenish hydraulic oil without filtering.
Turn off the hydraulic pump during shutdown to reduce the risk of idling pollution.
Pollution monitoring and intelligent maintenance trends
Online sensors: Real-time monitoring of oil particle count, moisture and temperature, and data access to the MES system.
Predictive maintenance: Analyze oil inspection data through AI to warn of filter blockage or oil quality deterioration in advance.
Quick oil change equipment: Integrated filtering and dehydration functions to shorten downtime.