Solenoid valve
Function in Plastic Machinery
The solenoid valve in plastic machinery primarily controls the fluid circuit, which in turn controls the forward and backward movement of the crankshaft. This process facilitates the opening and closing of the mold. The solenoid valve contains a closed cavity with through holes at various positions, connecting to oil pipes. The valve body manages oil discharge, allowing hydraulic oil to flow into different oil discharge pipes.
Role in Fluid Control
The solenoid valve is a basic automatic component used for fluid control, serving as an actuator for both hydraulic and pneumatic systems. It is essential for controlling the direction of hydraulic flow, particularly in factories where hydraulic systems power machines.
Working Principle
The solenoid valve’s operation relies on a closed cavity with multiple through holes, each leading to different oil pipes. A valve sits in the middle of the cavity, flanked by two electromagnets. When one of the magnet coils is energized, it attracts the valve body toward it. By controlling the movement of the valve body, various oil drain holes are either opened or closed, while the oil inlet hole remains open. This allows hydraulic oil to enter different oil discharge pipes, moving the piston, which drives the piston rod and ultimately controls the mechanical device’s movement. The entire system’s movement is regulated by controlling the electromagnet’s current.
Proportional Valve
Purpose in Plastic Machinery
The proportional valve plays a key role in adjusting the injection pressure and speed in plastic machinery.
Structure and Working Principle
The proportional valve is a hydraulic component consisting of a valve body and an oil-seal coil. Its working principle involves controlling the flow or pressure by adjusting the current in the oil-seal coil. There is a direct, proportional linear relationship between the current and the valve body’s flow/pressure opening degree. The valve can be categorized into two types: a proportional flow valve and a proportional pressure valve. This linear relationship is managed by the computer CPU processor and the electronic amplifier in the plastic machinery.
Flow and Pressure Control
The DSCA and DPCA ammeters in plastic machinery reflect changes in current corresponding to the voltage variations in the proportional flow and pressure valves. The electronic amplifier board outputs voltage to control the proportional valves, regulating oil pressure and flow. This ensures precise control over injection pressure and speed, which is crucial for applications requiring exact control over the movement of hydraulic cylinders or motors. The proportional relief valve offers smooth regulation of flow based on system requirements, ensuring system stability and reliability.
Pressure Regulation
In addition to controlling flow, the proportional relief valve also controls system pressure. By adjusting the valve core’s position, the system pressure is regulated within a specific range, preventing issues caused by excessive or insufficient pressure. This is essential for hydraulic systems requiring operation within a particular pressure range to prevent damage or failure.
Proportional Valve and CPU Control
Coordination with the Computer CPU
The relationship between the proportional valve and the computer CPU processor in plastic machinery is akin to the relationship between the human brain and limb organs. The CPU processor acts as the brain, while the electronic amplifier board functions like the nervous system, transmitting instructions. The CPU first processes input parameters and then sends signals to the proportional valve through the amplifier board, which controls actions during the injection molding process.
Applications Beyond Injection Pressure
Besides regulating injection pressure and speed, the back pressure proportional valve can control the screw’s movement, aiding mold opening and closing. It also enhances hydraulic system stability by reducing hydraulic shock and vibration, minimizing noise and energy loss. This is particularly beneficial in high-precision, high-stability hydraulic systems required by plastic machinery.
Safety Mechanism
Proportional Overflow Valve
The proportional overflow valve offers a critical safety mechanism. If the system pressure exceeds the set value, the valve automatically opens to release excess hydraulic oil back into the tank, preventing system overload and potential damage. This safety feature helps ensure the hydraulic system’s longevity and smooth operation.
