Electrical Control of Electric Injection Molding Machine

Electrical Control of Fully Electric Injection Molding Machine.

Comparative advantages with traditional hydraulic injection molding machines Compared with traditional hydraulic injection molding machines, the biggest advantage of all-electric injection molding machines is that they use servo motors for electrical control. Due to the innovative use of servo motors, each injection molding link of the all-electric injection molding machine can be controlled with high precision for a long time, which not only saves 50% to 70% of power consumption compared with traditional hydraulic drives but also saves hydraulic oil and cooling. cost of water. In terms of injection speed, the traditional hydraulic injection molding machine can achieve faster injection speed by using accumulator technology, but due to the limitation of the hydraulic valve and accumulator action characteristics, it cannot achieve lower injection speed. The speed control characteristics of the servo motor are relatively good, and it can be controlled from extremely low to extremely high speeds and has a wider speed adaptation range.

 

Electrical control of all-electric injection molding machine:

Working principle: The system integrates the culmination of advanced production process control methods in the injection molding industry, and realizes the three injection molding concepts of high efficiency, energy saving, and environmental protection. The working principle of the all-electric injection molding machine is to make full use of the thermoplasticity of the plastic, control the heating and melting of the plastic and the speed of flowing into the mold cavity through the servo motor, and then go through the pressure maintaining and cooling stages to form plastic products of various shapes. When processing the product, firstly measure and feed the material, heat it to melt and plasticize the raw material, then apply high pressure to inject it into the closed mold, and then open the mold after a period ofElectric Inject pressure maintaining and cooling, and finally eject the product to complete the whole process. Product injection molding process.

 

The characteristic requirements of the servo unit: The injection performance of the all-electric injection molding machine depends on the precise and stable characteristics of the servo control system to a very large extent, and the servo system is required to have the following four characteristics.

 

High precision: In order to ensure that the product can meet the requirements of precision injection molding, the servo control system must have high quality and high stability, so as to make the actions such as injection have very high precision. Therefore, not only the servo unit is required to have high positioning accuracy in position control, but also to provide high-precision speed regulation in speed control.

 

Fast response: In order to make injection molding of products with complex structures, multi-stage injection is often required. To ensure that the actuator strictly switches the forming parameters according to the preset requirements, not only the high positioning accuracy of the servo control system is required, but also the good characteristics of fast response and the ability to quickly respond to the tracking command signal.

 

Wide range of speed regulation: Whether it is an injection process or a mold clamping process, the actuator is required to operate within a relatively wide speed range. For example, in the process of driving the template to close the mold, in order to protect the safety of the mold, the mold clamping mechanism needs to switch from the high speed of the mold moving stage to the low speed when the mold is about to be closed, thus requiring the servo unit that drives the mold clamping mechanism to operate It can provide a wide range of speed regulation to realize the conversion between the highest speed and the lowest speed.

 

Large torque at low speed: When the injection molding machine is running at low speed, the feed servo system is required to have a larger torque output. In order to meet the above characteristic requirements, the all-electric injection molding machine also puts forward some corresponding requirements for the actuator of the servo system-

 

  • The servo motor is required to run smoothly within the entire speed range, and the torque The fluctuation of the servo motor should be small, especially when running at low speed, it should still maintain a stable speed without crawling
  • The servo motor is required to have a corresponding overload capacity to meet the characteristics of the system in terms of low speed and high torque.
  • The servo motor is required to have a small moment of inertia, a large stall torque, the smallest possible electromechanical time constant, and the smallest possible starting voltage to meet the characteristic requirements of the system’s rapid response.
  • The servo motor is required Can withstand frequent starting, braking, and reverse rotation.

 

Action control: In order to obtain high-quality injection molding products, the all-electric injection molding machine uses servo motors to realize the sequence and process control of the actions of each movement mechanism during the injection molding process, so as to ensure that the injection molding machine can complete the product production process according to the process requirements. The injection device of the all-electric injection molding machine is the key component to realize the three functions of plasticizing metering, injection, and pressure holding and feeding. Provide a set quantity, composition, and uniform temperature of molten material within a certain period of time; the second is to provide suitable injection speed and injection pressure according to the plastic properties and the structure of the product and inject the molten material into the mold cavity. 

All the movement process of injection molding is driven by the six servo motors of the Guangshu precision all-electric injection molding machine through motion coordination. Shown is the structure diagram of its main components. The motor that is coaxial with the injection screw and closely connected is called the injection servo motor, which plays the role of realizing the forward injection movement of the injection screw through the power transmission device. The motor parallel to the injection screw is called the sol servo motor, and its function is mainly to realize the rotation of the screw to make the granular raw materials forward. The motor used to translate the entire shooting platform is called the shooting platform moving servo motor, which is driven by the motor to complete the reciprocating motion of the shooting platform. The all-electric injection molding machine uses a servo motor as the driving device. The hardware framework of its control system mainly consists of six parts: man-machine interface, motion controller, logic controller, servo drive, temperature control unit, and sensor. Process program control is based on sensor information such as position, temperature, pressure, and speed, and multiple closed-loop links have been established to achieve high-precision electric injection molding machine processes. 

 

Final Thought:

For the control of the moving speed of the injection screw, the encoder signal installed behind the servo motor is used as the input signal, which realizes semi-closed-loop control compared to setting the speed command in the controller. For the control of injection pressure, it is a full-closed loop control of injection pressure formed by measuring the information of the pressure sensor behind the screw. As for the ultra-low-speed position control, the grating ruler is used to realize the closed-loop control. The key to the action control system of an all-electric injection molding machine lies in the high-speed processing of sensor signals such as temperature and pressure. The digital interface is used between the process program control device and the servo motor drive system, and only digital signals are transmitted between the two, and the anti-interference ability is particularly strong, so it can realize high-precision, fine-scale stable control.

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