At present, domestic injection molding electromechanical hydraulic control technology almost all use electro-hydraulic proportional technology, its technical feature is the use of three-way proportional speed control valve to control the speed. Although the electro-hydraulic proportional technology can greatly reduce the number of components, due to the use of quantitative pumps for fuel supply, there is always a flow-related energy loss in the work process, which has rarely been adopted in foreign countries.
Injection molding machine process is generally divided into clamping, injection, plasticization, pressure maintenance, cooling, open mold and other stages, each stage requires different pressure and flow. For the oil pump motor, the injection molding process is under a varying load condition. In the hydraulic system of the dosing pump, the oil pump motor provides a constant flow at a constant speed, and the excess hydraulic oil is returned through the relief valve. This process is called high pressure throttling. According to statistics, the energy loss caused by high-pressure throttling is as high as 36% to 68%.
In order to further reduce energy consumption and reduce noise, the plastics machinery manufacturers have made in-depth efforts to reduce energy costs and reduce energy costs. Extensive research and practice, such as Germany, Japan, and other countries have developed load-sensing injection-molded electromechanical and hydraulic control systems using a combination of variable displacement pumps and electro-hydraulic proportional valves as the most basic energy-saving method in electro-hydraulic control and have been widely used abroad. application. At present, in the energy-saving control technology of various injection molding machines, two kinds of energy-saving control systems, proportional variable pump and variable-frequency quantitative pump, have obvious energy-saving effects.
The proportional variable pump control system allows the user to set various operating pressures and speeds according to the injection molding process requirements and convert them into corresponding analog signals. The proportional pressure pump and the proportional flow valve are output to the proportional variable pump, and the set value is transmitted to the system. Output pressure and flow allow the hydraulic system energy output to follow the injection process load conditions to minimize energy loss. The variable frequency pump control system can make the energy output of the hydraulic system change along with the changing load conditions of the entire injection molding process, and maintains very low speeds in the pressure keeping, cooling and idling conditions, thereby achieving the purpose of energy saving. At the same time, using the synchronization signal of the injection molding machine and the electrical control system, the electro-hydraulic proportional control system is simulated into a load tracking control system, and the traditional quantitative pump is transformed into a variable-frequency variable pump, so that the oil return flow of the relief valve is reduced to the minimum without high pressure. Throttle energy loss, thus the traditional high-pressure throttling injection molding machine from energy-consuming upgrade to energy-saving.
Energy-saving technologies gradually become the focus of injection molding machine research and development
In the cost component of injection molding products, electricity charges account for a considerable proportion. According to the injection molding machine equipment technology, the consumption of the injection pump motor accounts for as much as 50% to 65% of the total power consumption of the equipment, and therefore it is also extremely energy-saving. Various advanced energy-saving control technologies aimed at reducing energy consumption are gradually becoming the focus of research on injection molding electromechanical systems.