This blog introduces a new hydraulic pump servo drive and control technology for injection molding machines. The AC permanent magnet synchronous servo motor is used to drive the hydraulic oil pump as the drive level control system of the injection molding machine to realize energy saving, fast dynamic response, stable pressure control, Excellent low-speed performance, and other performance improvements.
Through practical tests and applications, the new drive control technology plays an essential role in realizing the progress of energy-saving technology and the improvement of control precision of injection molding machines.
The composition of the drive and control system of the hydraulic pump servo of the injection molding machine:
The schematic diagram of the servo drive system of the hydraulic pump of the injection molding machine. The servo control system of the hydraulic pump of the injection molding machine is mainly composed of an AC permanent magnet synchronous servo motor, a servo driver, a hydraulic oil pump, a pressure sensor, an encoder, or a resolver.
This system provides a new concept of injection molding machine drive and control system, which can approach the energy-saving level of all-electric injection molding machines.
When the system is working, the whole machine controller of the injection molding machine converts the set value of the speed and pressure of the machine action into an analog signal or a digital signal and outputs it to the servo driver. The servo driver drives the servo motor to drive the hydraulic oil pump according to the requirements of the command signal. The speed and pressure control requirements correspond to the servo motor’s speed control and torque control.
Power consumption analysis of servo pump injection molding machine:
The hydraulic system of the servo pump injection molding machine is an essential part of the injection molding machine.
The working quality of the hydraulic system of the injection molding machine, such as the stability, reliability, repeatability, sensitivity, energy-saving effect, and low noise performance of the system, will directly affect the quality of the injection molded products and the dimensional accuracy, plastic molding cycle, and production cost will affect the Work environment, safe operation, and maintenance work.
The hydraulic system of the servo pump injection molding machine has the characteristics of high precision, high sensitivity, low noise, energy saving, proportional, servo control, and microprocessor.
The pressure and flow of the hydraulic control system of the servo pump injection molding machine in each injection cycle are changed according to the process requirements, that is, when the hydraulic system pressure executes each specific program, such as the driving force and speed of the actuator, there are particular requirements; therefore, the hydraulic system pressure and flow must be adapted to it.
The total energy consumption and output power of the hydraulic system of the servo pump injection molding machine are specific. Still, due to the different power consumption required to execute each program, the power consumption of the injection molding machine is in one cycle.
The oil pressure required for the mold clamping and mold opening system is low, and the time is short, generally 40% to 60% of a working cycle. The length of the time is related to the workpiece, and the interval is faster, which also Depends on the condition of the workpiece to be processed; it may be possible to process intermittently continuously.
Performance test experiment of hydraulic pump servo system:
Energy saving effect and its influencing factors: Due to the high energy conversion efficiency of the servo motor itself, the fact that the system flow and pressure output tend to be consistent with the load demand, and the servo motor can stop rotating when the machine is in the product cooling process, the hydraulic pump servo drive and control technology is used to save power for the injection molding machine. Performance is significantly improved.
Compared with the variable pump machine, it can save 20% to 50% of electricity, and compared with the fixed pump machine, it can save 30% to 60% of electricity.
The power-saving effect relates to product molding processes, plastic material properties, and system configuration schemes.
There are differences in power-saving performance between servo motors and drive control systems produced by different manufacturers.
For example, there is a specific difference in the moment of inertia and efficiency of the servo motor; the design of the brake circuit of the driver leads to a difference in the energy-saving effect; the type of hydraulic pump configured has a direct impact on the power saving performance of the hydraulic pump servo drive and control system. Plunger pumps, quantitative screw pumps, and double-displacement plunger pumps are used in different scenarios. Among them, the dual-displacement plunger pump system has the best power-saving effect.
Response speed and its influencing factors: Fast response speed is one of the technical advantages of the hydraulic pump servo drive and control system, which improves the machine’s ability to form precision products and operating efficiency.
The experimental data shows that the system’s response time reaches the fastest speed, and the highest working pressure is 40ms-50ms. In contrast, the response time of the exact specification variable pump system is 70ms-120ms.
The response time of the high-frequency response servo valve is 25ms-40ms.
The main influencing factors to improve the response speed are the displacement of the hydraulic pump configured in the system and the maximum speed of the servo motor.
The larger the hydraulic pump displacement of the same specification machine, the lower the maximum working speed of the motor and the faster the system’s response speed.
Pressure control accuracy and its influencing factors: In pressure maintaining and high-pressure clamping of the injection molding machine.
The machine needs pressure control. When the system is under pressure control, the speed of the servo motor is as low as 20.
150r/rain, under the working condition of low speed, the pressure fluctuates wildly.
The actual test found that the pressure control accuracy of different systems is quite different.
Through the performance test experiment of the hydraulic pump servo system, it can be shown that it has obvious technical advantages in reducing the energy consumption of the injection molding machine and improving the system response speed and pressure control accuracy.
It is foreseeable that the new system will replace the quantitative and variable pump systems currently configured on the injection molding machine and become the mainstream configuration scheme.
Now that the power supply is becoming more and more severe, energy saving is undoubtedly a relatively important topic. The energy consumption of injection molding machines is rather large, and energy saving is imperative.