Abstract: The Delta VFD-G injection molding machine dedicated frequency converter provides process synchronization operation signals through the injection molding machine controller, changing the motor speed to change the output flow of the oil pump. While meeting the speed requirements of the injection molding machine at each working stage, it reduces hydraulic system backflow, transforming the original fixed-displacement pump into an energy-saving variable-displacement pump with energy efficiency as high as 20-60%. It also features simple operation and accurate and stable speed control. Keywords: Delta VFD-G, injection molding machine, energy saving 1 Introduction In recent years, China's injection molding machine industry has achieved significant development driven by the market economy. According to relevant research data, by 2010, the global demand for plastic machinery equipment will increase at a rate of 3.5% per year, with injection molding machines accounting for approximately 38%. Faced with a huge market, the upgrading and replacement of injection molding machine equipment is accelerating. With increasingly stringent requirements from countries around the world regarding environmental protection, such as energy consumption, noise, and leakage control, the design and manufacture of a new generation of "energy-saving" injection molding machines has become an urgent issue that needs attention and resolution. Hydraulic transmission is the most commonly used transmission method in injection molding machines. Hydraulic injection molding machines are typical equipment with periodically varying loads. The working pressure and flow rate required at each process stage differ, resulting in significant load variations in the hydraulic system. Traditional electric fixed-displacement pump hydraulic systems rely on flow valves and pressure valves to regulate flow and pressure at different stages. Since the fixed-displacement pump's output power is not adjustable, excess energy is consumed by baffles, oil circuit leaks, and oil temperature rise. This not only wastes a significant amount of energy but also exacerbates wear on various valves, leading to excessively high oil temperatures, excessive motor noise, and shortened mechanical lifespan. Furthermore, the often large-capacity design of the fixed-displacement pump motor further contributes to energy waste. Therefore, improving the hydraulic system drive technology of injection molding machines is of universal significance for reducing energy waste and lowering the cost of injection molded products. 2. Injection Molding Process Principle The hydraulic transmission device of an injection molding machine mainly consists of an oil pump, hydraulic control valves, pressure electromagnetic proportional valves, flow electromagnetic proportional valves, various actuating cylinders, an oil pump motor, and other hydraulic accessories and pipelines. The electric quantitative oil pump unit converts the mechanical energy input from the electric motor into pressure energy, and then delivers hydraulic oil with a certain pressure and flow rate to the hydraulic components of the hydraulic system to meet the energy requirements of the hydraulic actuator to drive the load. Injection molding machines are mainly used for the molding of thermoplastic plastics. The injection molding process is a predetermined cyclical process. A complete production cycle mainly includes several stages: mold closing, mold locking, injection, pressure holding, melting, cooling, mold opening, and ejection. In this test, the sequence of steps—including mold closing, injection, material feeding, cooling, mold opening, and ejection pins—is used to achieve product molding. Figure 1 shows the current output waveform of the injection molding process. Injection molding machines typically use hydraulic transmission, and their structure includes an injection unit, a mold opening and closing unit, a hydraulic transmission unit, and an electrical control unit. The function of the electrical control unit is to ensure that the pressure, speed, temperature, time, position, and action program parameters of the injection molding machine work accurately and effectively, meeting the process requirements at each stage. The process parameters for injection molding machine operation (mold closing → injection unit infeed → injection → material feeding → cooling → injection unit retraction → mold opening → ejection) are shown in Figure 1. [align=center] Figure 1 Injection Molding Machine Process Diagram[/align] 3. Injection Molding Machine Dedicated Frequency Converter Solution 3.1 Delta VFD-G Injection Molding Machine Dedicated Frequency Converter Delta VFD-G is a dedicated frequency converter for injection molding machines. The Delta VFD-G frequency converter is a customized frequency converter specifically designed for injection molding machines, extrusion machines, blown film machines, blown bottle machines, air compressors, and hydraulic presses, etc., with variable loads and high overload drives. The specifications and characteristics of the Delta VFD-G series injection molding machine dedicated frequency converter include: unique overload capacity: 150% for 60 seconds; two 0-1A current signal input terminals; two analog output signals; segmented gain setting; built-in PID feedback function; two analog signals can be used for addition, subtraction, multiplication, and maximum value calculation; dedicated functions for injection molding machines; energy-saving operation and power consumption recording, etc. 3.2 Delta Injection Molding Machine Variable Frequency Drive Principle Design The Delta VFD-G inverter utilizes the existing flow and pressure control signals of the injection molding machine to convert the original fixed displacement pump into an energy-saving variable displacement pump. By providing process synchronization signals through the injection molding machine controller, the inverter principle changes the motor speed to alter the oil pump's output flow rate. While meeting the speed requirements of the injection molding machine at each working stage, it reduces hydraulic system backflow, transforming the original fixed displacement pump into an energy-saving variable displacement pump with energy efficiency reaching 20-60%. It also features easy operation, accurate and stable speed control, a soft-start device to reduce mold opening and closing vibration, avoid equipment impact and wear, extend equipment lifespan, and reduce motor noise. It is suitable for injection molding machines of various power and models. According to the working requirements of the injection molding machine, the synchronous control signal and electrical control of the upper computer (such as computer or PLC) of the injection molding machine are used to send out the analog signal (0-10VDC analog voltage signal), which is directly applied to the input terminal of the Delta VFD-FG frequency converter, thereby changing the output frequency of the frequency converter, that is, changing the speed of the oil pump motor, to change the output flow of the oil pump motor, so as to meet the oil pressure and flow rate required by the injection molding machine in each process, and transforming the traditional fixed pump into a variable pump. The block diagram of the injection molding machine frequency conversion control system is shown in Figure 2. [align=center] Figure 2 Block diagram of injection molding machine frequency conversion control system[/align] 3.3 Electrical principle design (Figure 3) [align=center] Figure 3 Electrical principle of injection molding machine frequency conversion drive[/align] 3.4 Frequency converter parameter design (1) The VFD-G frequency converter parameter settings are shown in Table 1. Table 1 VFD-G Inverter Parameter Design (2) Example of VFD-G Series VFD300FA3A-G Inverter Parameter Setting (Motor Model: Teco, 30HP/6P/380/50Hz/47.1A, EFF: 92.0%, PF=78.5%, 98rpm) is shown in Table 2. Table 2 VFD300FA3A-G Parameter Setting (3) Results of Fixed Displacement Pump-Variable Displacement Pump Operation Experiment are shown in Table 3. Table 3 Results of Fixed Displacement Pump-Variable Displacement Pump Operation Experiment 4 Conclusion Delta servo-type plastic machine dedicated inverter, in conjunction with an AC servo motor, is equipped with a rotary encoder and pressure sensor to collect flow and pressure respectively. By changing the speed and torque of the servo motor, closed-loop control of flow and pressure is achieved. After trials by multiple injection molding machine manufacturers, injection molding machines equipped with Delta's servo-type dedicated injection molding machine controller have demonstrated superior performance. In addition to achieving energy savings of 20%-60% compared to traditional injection molding machines and significantly improved precision, their servo motors offer rapid response, increasing pressure from 0 to 175KG in just 40ms. Furthermore, the low hydraulic oil temperature eliminates the need for cooling, thus reducing workshop temperatures. The successful adoption of Delta's servo-type dedicated injection molding machine controller has brought significant economic and technological benefits to injection molding machine manufacturers in their pursuit of energy-efficient, precise, environmentally friendly, and high-speed product quality.