The hydraulic control system of CNC bending machine consists of hydraulic control and sensors. Hydraulic control and energy conversion mainly include core components such as hydraulic control valves and hydraulic pumps. As an important branch of automatic control system, hydraulic control technology occupies a key position in CNC bending machine system with its remarkable characteristics and many advantages.
Hydraulic control technology is essentially an electro-hydraulic hybrid technology, such as an electro-hybrid system, which organically integrates mechanical system, electronic system and hydraulic system. At present, hydraulic control system is widely used in equipment manufacturing, automobile industry, aerospace and metallurgy.
This article introduces the electro-hydraulic control system of bending machine in detail. The system can be divided into open-loop control system and closed-loop control system, in which the bending machine crossbeam is the main control part of the system.
1. Closed-loop System
The closed-loop control system is also called feedback control system. The system compares the measured value of the output with the expected given value, generates a deviation signal, and controls and adjusts the deviation signal to make the output value approach the expected value.
For example, when driving a car, the human brain first forms a preliminary perception of the direction of the car. During driving, the driver observes and compares the actual driving direction with the expected direction, and constantly adjusts the steering wheel to gradually approach the target direction, which forms a closed-loop control process.
Closed-loop control is adjusted according to the real-time operation of each component of the CNC bending machine, and has the characteristics of high precision and fast response speed. However, due to the large number of elements involved in the closed-loop control system, it is more complex than the open-loop system and the cost is correspondingly higher.
“The closed-loop control system can improve the bending accuracy to ±0.01mm, which is suitable for sheet metal processing scenarios with high precision requirements such as aerospace and medical equipment.” —- Excerpted from “Modern Hydraulic Control System”, Machinery Industry Press, 2023
| Key parameters of closed-loop system | Typical value | Application field |
|---|---|---|
| Bending accuracy | ±0.01-0.03mm | Precision electronics, medical, aviation |
| Response time | <10ms | High-speed production line |
| Feedback frequency | 500-1000Hz | Precision control system |
2. Open-loop System
Open-loop is a concept relative to closed-loop, that is, open-loop control will not feedback the control results of the current system. For example, when throwing an object, once the object leaves the hand, the person can no longer control its trajectory, because once the object leaves the hand, the person’s control over it has ended.
Therefore, in the open-loop system of the CNC bending machine, the bending accuracy mainly depends on the inherent accuracy of the various components of the machine tool. The system cannot control and compensate for the parameter changes during the bending process, resulting in relatively low bending accuracy. Once the machine tool is disturbed by external interference, its internal parameters will change. However, from the perspective of system design, the open-loop design is simpler and more stable, and it is more convenient for both early installation and later maintenance.
3. System Selection Reference
According to the 2024 issue 2 of “International Metal Processing Technology”, in the global sheet metal processing industry, about 65% of small and medium-sized enterprises choose open-loop systems, while 35% of enterprises (mainly large or professional precision processing enterprises) choose closed-loop systems. This choice mainly depends on product accuracy requirements and investment budgets.
| Influencing factors | Open-loop system | Closed-loop system |
|---|---|---|
| Initial investment | Low (baseline) | 30-50% higher |
| Maintenance cost | Low | Medium to high |
| Applicable plate thickness | 0.5-10mm | 0.3-20mm |
| Typical applications | Building components, furniture, general industrial use | Precision machinery, electronic equipment housing, medical equipment |
Conclusion
In summary, if the buyer has high requirements for bending accuracy when purchasing a CNC bending machine and has sufficient funds, it is recommended to purchase a bending machine with a closed-loop system; if the bending accuracy requirements are not high, a bending machine with an open-loop system can also meet basic needs.
“The correct selection of a control system should consider factors such as product accuracy requirements, production scale, and investment payback period, rather than blindly pursuing high-end configurations.” —- Quoted from “Sheet Metal Processing Equipment Selection Guide”, China Mechanical Engineering Society, 2023
