Application of VFD (Variable-frequency Drive) for Sunwoele injection molding machine

I. Overview

At present, the vast majority of injection molding machines are hydraulic transmission injection molding machines. The power in the hydraulic transmission system is provided by the motor driven oil pump. The hydraulic oil pump is a positive displacement oil pump, which is divided into two types: quantitative pump and variable pump; There are some problems that need to be solved, so the most commonly used ones on the market today are quantitative pumps.

The general plastic parts production process has the following links: film locking, glue injection, melting glue, pressure holding, cooling, and film opening. Injection molding machines require different flow rates and pressures in different processes, and must rely on proportional flow valves and proportional pressure valves to adjust the required flow rates and pressures in different processes.

2. Principle of energy saving

Quantitative pumps can adjust the flow rate by adjusting the speed. Using VFD (Variable-frequency Drive) to adjust the speed of the oil pump motor and then adjust the flow rate is currently the most ideal energy-saving adjustment method. VFD (Variable-frequency Drive) is to follow the signals of the proportional flow valve and proportional pressure valve, control the oil pump motor speed in real time to adjust the oil volume, meet the needs of each link, and can control the overflow to the minimum state, thus saving energy.

Accurately adjust the rotation speed of the oil pump through VFD (Variable-frequency Drive), so that the actual oil supply of the oil pump can meet the working flow required by the injection molding machine, which not only meets the production needs but also achieves the purpose of energy saving. Usually, the effect of 20%-50% power saving of the oil pump motor can be achieved.

3. Power-saving principle and transformation analysis

1. Analysis of process energy saving

The molding process of the injection molding machine is a predetermined periodic action process, that is, mold closing - nozzle advance - injection - holding pressure - sol, cooling - mold opening - ejection product - ejector rod retraction - mold closing and other processing procedures To achieve a certain product molding. In a traditional injection molding machine, the hydraulic transmission device is mainly composed of a pump, a hydraulic control valve, a pressure electromagnetic proportional valve, a flow electromagnetic proportional valve, various action cylinders, an oil pump motor and other hydraulic accessories and pipelines. The oil pump is a quantitative pump. Motors typically provide rated power and speed. The oil pump converts the mechanical energy input by the motor into pressure energy, and then delivers hydraulic oil with a certain pressure and flow to the hydraulic components of the hydraulic system to meet the energy requirements of the hydraulic actuator to drive the load.

2. The wiring diagram for frequency conversion transformation is as follows:

Using Sunwoele VFD (Variable-frequency Drive) in the original injection molding machine system is easy to install and is very suitable for retrofitting on existing injection molding machines.

4. The technical advantages of Sunwoele injection molding machine dedicated VFD (Variable-frequency Drive)

1. The starting torque is large, and 0.5Hz can reach 150% of the rated torque; the dynamic response is fast.

2. The corresponding relationship between VFD (Variable-frequency Drive) analog input and the corresponding frequency can be set as broken line, and two inflection points can be set to meet the strong force required for mode locking.

3. It can directly accept the current signal of 0-1A and the voltage signal of 0-10V, and can directly obtain the speed control signal from the proportional flow valve, and it is two independent signals, which is convenient for the superposition of pressure and flow signals.

4. The two-way signals are isolated for power supply, which reduces mutual interference.

5. In order to facilitate customers' transformation, we specially designed an integrated control cabinet for injection molding machines, with built-in power and frequency conversion conversion. When VFD (Variable-frequency Drive) fails, normal production will not be affected.

6. The injection molding integrated control cabinet has a reasonable structure and beautiful appearance, and can be installed next to the injection molding machine and integrated with the injection molding machine.

V. Conclusion

The use of VFD (Variable-frequency Drive) dedicated to Sunwoele injection molding machines has the characteristics of high power saving rate, strong reliability, soft start, and easy operation. All investment can be recovered by saving electricity in about 6-12 months.