In modern injection molding technology, servo valve is a key control element in hydraulic system, and its control accuracy and response speed directly affect the quality and production efficiency of injection products. Therefore, the control mode and technology of injection molding machine for servo valve are particularly important. This paper will discuss the basic principle, control mode and application of servo valve in injection molding machine.
First, the working principle of servo valve
Servo valve is a kind of hydraulic control valve with high precision and high frequency response, which can continuously and accurately control the flow and pressure of hydraulic system according to input signals (usually electrical signals). Its core components include torque motor, nozzle baffle mechanism and slide valve. The deflection of the torque motor is controlled by the electric signal, which drives the baffle to move, thus changing the flow direction and flow rate of hydraulic oil and realizing the motion control of the actuator (such as hydraulic cylinder or hydraulic motor).
Because of its high responsiveness and high control accuracy, servo valves are widely used in situations that require high dynamic response and high positioning accuracy, such as injection and mold opening and closing of precision injection molding machines.
Second, the control mode of injection molding machine to servo valve
In the control system of injection molding machine, closed-loop control is usually used to drive and adjust the action of servo valve. Closed-loop control consists of the following parts:
1. Controller: Generally, PLC (programmable logic controller) or special electronic control system of injection molding machine is used to generate control signals according to the set process parameters.
2. Servo amplifier: converts the digital or analog signal output by the controller into a current signal suitable for the servo valve to drive the torque motor of the servo valve.
3. Servo valve: receives the signal output by the servo amplifier and adjusts the flow and pressure of the hydraulic system.
4. Feedback devices, such as displacement sensors and pressure sensors, are used to monitor the state of the actuator in real time and feed back the information to the controller to form closed-loop control.
Through this closed-loop system, the injection molding machine can accurately control the speed, position, pressure and other parameters to meet the needs of complex molding process.
Third, the application example of servo valve in injection molding machine
In practical application, servo valves are mainly used in the following aspects:
1. Injection control: the injection speed and pressure are adjusted by controlling the servo valve, and different injection curves are realized at different stages, thus ensuring the dimensional accuracy and surface quality of the product.
2. Clamping control: The servo valve can realize the smooth and impact-free moving die movement during the die closing process, protect the die and improve the production safety.
3. Ejection control: the servo valve is used to realize the precise control of ejection action, so as to avoid the damage of products caused by excessive ejection force.
In addition, with the improvement of energy-saving requirements, the servo energy-saving system combined with servo valve and variable pump has gradually become the mainstream, and remarkable energy-saving effect is achieved by supplying oil on demand.
IV. Conclusion
To sum up, the servo valve plays the role of “executive center” in the injection molding machine, and its performance directly affects the control accuracy, response speed and energy consumption level of the whole machine. Through the reasonable control of servo valve, not only the quality of injection molding products can be improved, but also the automation level and energy efficiency ratio of equipment can be improved. With the development of intelligent manufacturing and Industry 4.0, the servo valve will continue to evolve in the direction of higher precision and intelligence in the future, which will bring more possibilities to the plastic processing industry.