The injection molding hydraulic system is the driving force behind the machine, responsible for key operations such as mold closing, injection, and ejection. Its operating status directly impacts the machine’s efficiency, part quality, and equipment lifespan. The hydraulic system, comprised of components such as the hydraulic pump, cylinder, valve, tubing, and tank, operates under high pressure and high speed for extended periods, making it susceptible to failures due to oil contamination, component wear, and seal aging. Therefore, scientific and standardized maintenance is crucial to ensuring stable hydraulic system operation. This not only reduces downtime and maintenance costs, but also extends the lifespan of the equipment. Hydraulic system maintenance requires a comprehensive maintenance system encompassing oil management, component inspection, cleaning, and maintenance, ensuring the system is always in optimal working condition.
Regular hydraulic oil replacement and contamination control are key maintenance tasks. Over long-term use, hydraulic oil can degrade due to factors such as high temperatures, oxidation, and contaminants. These factors can lead to decreased viscosity, poor lubricity, and increased corrosiveness, further exacerbating wear on hydraulic components. Therefore, hydraulic oil replacement should be done regularly based on the hydraulic system’s operating environment and frequency of use. Generally, the hydraulic oil should be replaced after the first three months of use or after 500 hours of operation for a new machine. Thereafter, the oil should be replaced every 2,000-3,000 hours of operation or annually. When replacing hydraulic oil, the tank must be completely drained and the tank, oil filter, and other components must be cleaned to prevent residual contaminants from mixing with the new oil. Furthermore, hydraulic oil contamination must be strictly controlled and regularly checked for cleanliness. An oil contamination meter can be used to ensure that the oil contamination level does not exceed NAS Level 8. Furthermore, a dedicated filter refueling device must be used during refueling to prevent airborne impurities such as dust and moisture from entering the system. A high-efficiency air filter should be installed in the tank’s air vent to prevent contaminants from entering the oil.
Routine inspection and maintenance of hydraulic system components are crucial for preventing failures. The hydraulic pump, the system’s power source, requires regular inspection. Check its operating status and verify its normal operation. Any unusual noises may be caused by poor oil suction, bearing wear, or blade damage, requiring prompt shutdown and inspection. The operational flexibility of hydraulic valves (such as reversing valves, pressure valves, and flow valves) directly impacts system control accuracy. Regular inspections are required for spool sticking and solenoid function. Valve performance can be verified manually or by voltage testing, and any problems should be replaced promptly. The hydraulic cylinder, the actuator, requires inspection of its piston rod for scratches and deformation, and for seals for aging and leakage. If leaks are detected, replace the seals promptly to avoid oil waste and environmental pollution. Furthermore, oil lines and joints should be inspected for aging, damage, deformation, and loose joints for leakage. High-pressure oil lines, in particular, should be replaced immediately if damaged to prevent accidents involving high-pressure oil injection.
Cleaning and maintaining a hydraulic system is crucial for stable operation. The cleanliness of the oil tank directly impacts the quality of the fluid. Regular cleaning is essential, typically every six months or when the hydraulic oil is changed. Use a lint-free cloth or specialized cleaning tools to remove contaminants such as sludge and impurities from the tank’s interior. After cleaning, flush with fresh oil to ensure no residual impurities remain. The oil filter is a key component in preventing contaminants from entering the system and requires regular cleaning or replacement based on usage. The suction filter is typically cleaned every one to two months, while the pressure and return filters require timely replacement based on differential pressure alarm signals to prevent increased pressure loss or oil contamination caused by filter clogging. External cleaning of the hydraulic system is also crucial. Regularly clean equipment surfaces from oil and dust, and keep the heat sink clean to ensure proper heat dissipation and prevent oil deterioration and system failures due to excessive oil temperatures.
Parameter monitoring and performance testing of hydraulic systems are effective means of promptly identifying problems. Hydraulic system parameters such as operating pressure, flow rate, and oil temperature should be regularly monitored to ensure they operate within their design ranges. System operating pressure should generally not exceed 90% of the rated pressure. Abnormally high pressure may be due to factors such as excessive load or a stuck valve. Low pressure may be caused by leaks or pump failure and requires prompt investigation. Oil temperature is a key factor affecting hydraulic system performance and should generally be maintained between 30°C and 55°C, with a maximum temperature not exceeding 60°C. Excessively high oil temperatures accelerate oil oxidation and seal degradation. The cooling system, including the cooling fan and cooler, should be checked for proper operation. If necessary, cooler scale should be removed or the cooling medium replaced. Additionally, regular system performance testing is required, such as testing the hydraulic cylinder’s movement speed, positioning accuracy, and system response time. These should be compared to the equipment’s factory specifications. Any performance degradation should be analyzed and appropriate maintenance measures implemented.
Establishing a comprehensive hydraulic system maintenance record and management system is crucial for improving maintenance effectiveness. A hydraulic system maintenance file should be created for each injection molding machine, recording the time, content, replaced parts, oil brand and model, system parameters, and other information for each maintenance session. This facilitates tracing the system’s operating status and maintenance history. A detailed maintenance plan should be developed, clearly defining the content and cycles for daily, scheduled, and special maintenance. Responsibilities should be assigned to individuals to ensure timely and quality maintenance. Training for operators and maintenance personnel should be strengthened to ensure they master the basic principles of hydraulic systems, common fault diagnosis, and maintenance skills, enhancing their sensitivity to and ability to handle system anomalies. Furthermore, a contingency plan should be established to ensure prompt and effective response to sudden hydraulic system failures, minimizing the impact on production. Through scientific management and standardized maintenance, the reliability and service life of hydraulic systems can be significantly improved, providing a strong guarantee for the smooth operation of injection molding production.
