Closed loop #
Closed loop is also called feedback control system.
The system compares the measured value of the system output with the expected given value, so as to generate a deviation signal, and then uses the signal deviation to control and adjust, so that the output value can be close to the expected value.
For example, when driving, people first have a preliminary perception of the driving direction of the car in their brain. During the driving process, people observe the driving direction of the car with their eyes, compare the driving direction of the car with the desired direction, constantly adjust the direction in the process, and finally make the driving direction of the car close to the target direction, Thus, a closed-loop control is formed.
Closed loop control is based on the operation of each part of the machine tool, with high accuracy and response speed.
Because the closed-loop control system involves many elements, compared with the open-loop system, the structure of the whole system is more complex and the price is higher.
Open loop #
The open-loop control is compared with the closed-loop control, that is, the open-loop control does not feed back the current system control results.
For example, throw things. Once something is thrown, people can’t control what is thrown. Because once things leave hands, people’s control over things immediately stops.
Therefore, in the open-loop system of the press brake machine, the accuracy of bending depends on the accuracy of each part of the machine.
The system can not control and compensate the parameter changes in the bending process, resulting in low bending accuracy.
Once the outside of the machine tool is disturbed, the internal parameters of the machine tool will change.
However, in terms of system design, open-loop design is simpler and more stable.
Both the installation of the machine tool in the early stage and the maintenance of the subsequent machine tool are simpler.
To sum up, when purchasing a press brake machine, if the buyer has high requirements for bending accuracy and sufficient purchase funds, it is recommended that to buy a press brake with closed-loop system; If the requirements for bending accuracy are not high, the press brake with open-loop system shall be selected.