What are the key technologies of servo press?

Release time：2024.06.15

1. Using servo motor to directly drive the main oil pump of the hydraulic press to achieve energy saving.

At present, there are still many difficulties in using high-power servo motors to directly drive hydraulic pumps. The main requirement is that the speed range of the hydraulic pump is very large. Generally, the minimum speed of a hydraulic pump is 600 r/min, and the hydraulic pump can still work normally even below 10 r/min.
The appearance of high-power AC servo motors and their control technology is a new product in the past decade. Currently, the main application in technology is the switched reluctance motor (SMR), which has the advantages of simple and reliable operation, high efficiency operation in a wide range of speeds and torques, operation in four quadrants, fast response speed, and low cost. Its disadvantages are: large torque fluctuations, high vibration; the system has nonlinear characteristics, high control costs, and low power density.
The AC servo motor drive control unit is composed of large-scale integrated circuits, high-power rectifier modules, and other electronic power components. With the development of electronic technology, the performance of the AC servo motor drive control unit continues to improve, the price keeps dropping, promoting the realization and popularization of high-power AC servo drive technology, and providing the possibility of adopting AC servo drive in the field of forging and pressing equipment. The research focus is to concentrate scientific research efforts, develop high-power AC servo motor control technology with independent intellectual property rights, and related application technologies, providing a solid foundation for the development of servo presses.

2. Implement closed-loop control of hydraulic pressure and position by changing the speed of the servo motor.

The technology of using servo motors to achieve closed-loop control of hydraulic pressure and position in hydraulic machines is not very mature. Traditional hydraulic machines control hydraulic pressure and position through proportional valves and proportional servo valves. Special control algorithms need to be studied to ensure high stability and precision of hydraulic pressure between 1-25 MPa.

3. Research on energy recovery and energy management systems.

In order to achieve greater energy savings and minimize energy loss, it is necessary to recover and reuse the potential energy from the slider's gravitational descent and the energy generated when the oil cylinder is depressurized. Currently, there are no mature practices or experiences in this area. In terms of energy management, due to the instantaneous power being many times greater than the average power, energy allocation needs to be well managed in large servo hydraulic machines to avoid causing impact on the power grid.

4. Development of specialized control systems.

Since many existing hydraulic machines use PLC control, it is difficult for standard PLCs to meet the requirements of servo hydraulic machines which use hydraulic and speed closed-loop program control that require large computational power. Control systems for servo hydraulic machines need to be controlled using industrial PCs, and therefore, specialized control systems must be developed.

5. Optimization of forming processes based on servo hydraulic machines.

Different materials and shapes of stamping parts lead to drastically different stamping processes. For example, in the process of quiet cutting and shearing, control of the speed change point is crucial. The reverse extrusion forming of magnesium alloy cup parts requires the slider to undergo 4 different speeds within one work cycle, with constant pressure control during the extrusion process. Therefore, the superiority of servo hydraulic machines can only be realized when combined with various form optimization processes. Researching the forming mechanisms of various forming processes, establishing optimized parameters suitable for the forming process, is crucial for improving product quality, production efficiency, and reducing production costs.

6. Optimization design of the body of servo hydraulic machines.

Compared to traditional hydraulic machines, servo hydraulic machines have the advantages of energy saving and noise reduction, requiring more considerations in body design, including various possible extreme working conditions, working frequencies, and complexity of stamped parts. In the past, domestic engineering and technical personnel mainly used empirical methods and analogies with similar products for design. Domestic forging machine products have disadvantages such as large volume, heavy weight, and poor control accuracy, with steel consumption being a key factor in controlling the production costs of forging machine manufacturing companies. Domestic scholars and engineering technicians have developed optimization software for the local optimization of the body parts of forging machines, but mainly at the static design stage. Not much consideration is given to the dynamic machining process of the machine tool system, resulting in fundamental reliability issues of the machine tool not being resolved, leading to reduced machine tool lifespan and increased maintenance costs. Therefore, the design of servo hydraulic machine bodies needs to establish a design method and technical system under the constraints of forging machine rigidity, strength, and dynamic performance, narrowing the design and manufacturing gap with developed countries.