According to the driving theory of the injection molding machine, the control system of the injection molding machine is composed of various circuits for processing power and controller to complete the movement and process actions
The electric injection molding machine uses a servo motor to perform injection, plasticization, mold clamping, ejection, Therefore, it has high controllability and response characteristics
☆Features of electric injection molding machine:
-Since each action (injection, plasticization, melting, clamping and ejection) has independent servo motor drive, the electric injection molding machine consumes less energy than the hydraulically driven injection molding machine;
-The use of cooling water to control the oil temperature is reduced because no hydraulic oil is used;
-An oil-free environment is possible (no oil pollution);
-Because there is no vibration problem in the hydraulic circuit of the traditional hydraulic system, low noise levels are possible during operation;
-By using a high-precision servo motor, complete closed-loop control that reduces position and velocity fluctuations is easy to perform.
However, compared with hydraulically driven injection molding machines, the disadvantages of electric injection molding machines are as follows:
If the electric injection molding machine is close to full load operation, such as high injection pressure or high holding pressure, the servo motor often interrupts the forming operation due to overload. (that is, limiting the power of large electric injection molding machines)
The action of the electric injection molding machine is controlled by the servo motor, so it is different from the hydraulic injection molding machine when setting the process. The operation principle of the electric injection molding machine is described below.
It consists of 5 actions, each of which is as follows:
The rotary motion of the servo motor is converted into a linear motion by the ball screw and the synchronous tooth belt to complete the injection, holding pressure and back pressure. The movable plate connected to the ball screw moves forward.
The forward movement of the plate integrated with the ball screw pushes the screw forward.
According to the value set by the molding, the injection speed is controlled by controlling the rotation speed of the servo motor, and the injection pressure is detected by the load cell located between the moving plate and the ball screw nut, and the detected signal is directly fed back to the pressure control.
In the plasticizing stage, the rotational motion of the servo motor is used for the rotation of the screw through the timing belt.
During the rotation of the screw, the back pressure formed by the molten plastic accumulated in the head of the screw pushes the screw to move backward, and the back pressure is adjusted by adjusting the load of the servo motor.
The more important part of the injection unit is: the nozzle contact
device of the electric injection molding machine
In order to prevent the nozzle and mold from coming off due to high polymer pressure and the plastic melt from leaking between the mold and the nozzle, a high nozzle contact force is necessary. (You can observe the operation diagram of the motor injection unit).The steps are as follows:
For the electric injection molding machine, the geared motor is used as the driving source, and the rotational motion generated by the geared motor is linearly moved by the synchronous toothed belt and the ball screw to realize the forward and backward movement of the injection unit.
When the nozzle contacts the mold mounted on the fixed stencil, the injection unit cannot move forward.
The spring is compressed to provide braking, and when the spring is compressed to the set value provided by the brake, the contact force requirement of the nozzle is reached.
The rotary motion of the mold-cut servo motor is converted into a linear motion by the timing belt and the ball screw, and the toggle device is the same as the toggle device of the hydraulic mold clamping device. Opening and closing of the mold by a ball screw in the middle of the toggle system
The ejector device is used to separate the product and the mold when the mold is opened after the injection, pressure keeping and cooling are completed, and the rotary motion generated by the ejector servo motor is converted into a linear movement by the ball screw, and the ball screw is connected. The ejector rod connected to the ejector plate ejects the product from the moving plate.
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