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The hydraulic system of a hydraulic press is one of its two major components. Its function is to control the hydraulic press and its auxiliary mechanisms to complete various strokes and actions through various hydraulic components. The design, manufacturing level, and quality of the hydraulic system (including the hydraulic components used), as well as the quality of its use, adjustment, and maintenance, have a significant impact on whether the hydraulic press can operate normally. A correct understanding of the working principle of the hydraulic system is essential for understanding the working performance of the hydraulic press and fully utilizing its functions. It also provides a basis for the correct use of the hydraulic press to complete various forming processes. The hydraulic systems of hydraulic presses mostly fall within the high-pressure, high-flow rate range. It must universally and accurately meet the various process requirements of pressing workpieces, while also saving energy and improving energy utilization as much as possible. Therefore, there are common requirements for the hydraulic system of a hydraulic press, which can be summarized as follows:

(1) In terms of operating characteristics, it is required to be able to realize adjustment actions for the mold, manual operation, and semi-automatic operation.

(2) In terms of stroke speed, it is required to be able to achieve fast empty stroke movement and fast return stroke movement to save auxiliary time.

(3) The working fluid pressure is generally 20-32 MPa. For those with a smaller rated pressure and larger structural space, a lower working pressure is used. For workpieces with high unit deformation pressure, a higher working fluid pressure is used for presses with a large rated pressure and a relatively small table size.

(4) In terms of process characteristics, small hydraulic presses generally do not perform pressure grading, while medium and large hydraulic presses generally require graded rated pressure to meet the needs of different processes.

(5) At the end of the working stroke, before the return stroke begins, it is generally required to pre-unload the main cylinder to reduce impact and vibration during the return stroke. These are some of the small requirements for the hydraulic system of a hydraulic press. But do you know what to pay attention to during the long-term operation of the hydraulic system?

Hydraulic presses are used for pressure processing in processes such as molding, pressing, cold stamping, and bending. They are among the earliest applications of hydraulic transmission. The hydraulic system is used for the main drive of the machine, mainly pressure-controlled, with high system pressure, large flow rate, and high power. Special attention should be paid to how to improve system efficiency and prevent hydraulic shock. The operation of the hydraulic system of a hydraulic press generally requires the following basic actions for the main cylinder's work cycle: fast forward - deceleration approach to the workpiece and pressurization - pressure holding delay - pressure relief - fast return and keeping the piston at any position of the stroke. When there is a load cylinder, if topping is required, the action cycle of the topping cylinder is generally piston rising - stop - downward retraction. Thin plate stretching requires the oil-pushing cylinder to rise - stop - pressure return, etc. Sometimes, a side pressing cylinder is also needed to press the material tightly. Therefore, faults occur in this work cycle. So how to avoid faults in the hydraulic system?

1. Prevent air from entering the system and promptly remove any air that has entered the system. Air entering the hydraulic system will cause noise and oil oxidation and deterioration. Measures must be taken to prevent air from entering, and air that has entered the system must be frequently discharged.

2. Keep the oil clean at all times. Impurities mixed in the oil will cause the slide valve to jam, block the throttle holes or gaps, preventing the hydraulic components from working normally, and increasing the wear and tear of the relatively moving parts. In addition to installing oil filters and various devices to prevent external impurities from entering the system, the oil filter should be cleaned and the old oil replaced regularly. During the assembly of the hydraulic system, each hydraulic component and pipe should be cleaned. After the test run, it is best to remove each component and pipe, clean them thoroughly, and then reinstall them.

3. Prevent leakage. External leakage is not allowed, while internal leakage is unavoidable, but the leakage amount cannot exceed the allowable value. If the leakage is excessive, the pressure will not rise, and the hydraulic motor will not reach the expected force (or torque). The amount of oil leakage is related to the pressure, which will make the movement of the working parts unstable. In addition, due to excessive leakage, the volume loss increases, and the oil temperature rises. To avoid excessive leakage, there should be an appropriate gap between the relatively moving parts and appropriate sealing devices should be installed.

4. Prevent the oil temperature from becoming too high. The oil temperature of a general hydraulic system should be maintained at 15-50℃. Too high oil temperature will bring a series of adverse consequences. The rise in oil temperature will cause the oil to become thinner, increase leakage, and reduce system efficiency. Oil working at higher temperatures is prone to deterioration. To avoid excessive oil temperature, in addition to taking measures to avoid oil heating in the design (such as oil pump unloading and the use of volume control for high-power systems), it is also necessary to consider whether the oil tank has sufficient heat dissipation capacity. If necessary, a cooling device can be added.