Detailed explanation of the working principle of the hydraulic system in injection molding machines

Detailed explanation of the working principle of the hydraulic system in injection molding machines
A.The basic composition and power transmission of hydraulic systems The hydraulic system of an injection molding machine mainly consists of a hydraulic pump, a control valve group, an actuator cylinder, an oil tank, and pipelines. Its working principle can be summarized as follows: the motor-driven hydraulic pump (usually a plunger pump or gear pump) converts mechanical energy into hydraulic energy, and the oil is distributed to each cylinder through pressure regulating valves (such as proportional valves) to push the mold to complete actions such as mold closing, injection, and pressure holding. Taking the common 2500 ton injection molding machine as an example, the system working pressure can reach 21MPa (data source: "Plastic Machinery Design Manual"), and the high-pressure oil is precisely controlled for flow through a servo valve, with an error range of ± 0.5%.

B. Core link: Dynamic regulation of pressure and flow rate 1. Flow matching: The injection speed is achieved by adjusting the pump displacement through a servo motor, and the flow rate can reach 300L/min during high-speed injection (data source: Klaus Maffei Technical White Paper); 2. Pressure control: The system adopts dual regulation of overflow valve and proportional pressure valve. For example, during the pressure holding stage, it is necessary to maintain a pressure of 15-20MPa to prevent product shrinkage marks; 3. Energy saving design: The new variable displacement pump can reduce energy consumption by 30%, while the efficiency of traditional quantitative pump systems is only 60% -70%, while servo hydraulic systems can reach over 90%.

C. Collaboration of execution agencies and fault protection 1. Injection cylinder: equipped with displacement sensor, repeat positioning accuracy ± 0.01mm; 2. Mold closing cylinder: using a differential circuit to accelerate the idle stroke, the formula for calculating the closing force is F=P × A (P is the oil pressure, A is the piston area); 3. Safety mechanism: The pressure relay monitors in real-time and cuts off the oil circuit within 0.1 seconds when overpressure occurs. 4、 Key points of technological evolution and maintenance The current electro-hydraulic hybrid system (such as fully electric injection molding machines) is gradually replacing pure hydraulic design, but hydraulic systems still dominate in medium and large-scale equipment. Daily attention should be paid to oil temperature (recommended ≤ 55 ℃), filter cleanliness (NAS level 8 standard), and oil viscosity (commonly used in ISO VG46). Regularly replacing seals (with a 2-year cycle) can prevent 80% of leakage failures.


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