As an experienced engineer in the field of hydraulic machinery, I have often faced the challenges associated with shock absorption in large prensa hidráulica machines. The design and application of shock-absorbers for large hydraulic press machines is crucial for enhancing performance and ensuring operator safety. In this article, I will explore the key design principles, materials, and techniques that contribute to effective shock absorption. By understanding these elements, we can significantly improve the reliability and efficiency of hydraulic presses, ultimately leading to better production outcomes. Let’s delve into the innovative solutions that make this possible.

Design background

With the rapid development of the machinery industry, prensas hidráulicas as forging equipment are constantly moving towards large-scale, automated, precise and intelligent directions, and at the same time need to meet the requirements of low-carbon economy and green environmental protection development advocated by the state.

When the sheet metal is punched, due to the sudden reduction or disappearance of the resistance to deformation of the material, a load loss phenomenon will occur, which often causes the hydraulic press body to be subjected to extreme shock vibration, accompanied by harsh noise. The beam is broken and the foundation is damaged. Severe noise pollution can also cause serious harm to workers’ health. Controlling harmful vibration and reducing noise has become an urgent problem to be solved.

The punching shock-absorber principle

O prensa hidráulica moves downward through the slider to drive the forming mold fixed on it to close the mold quickly, so that the metal sheet is permanently deformed to obtain the final formed part. The main principle of the vibration and impact of the hydraulic machine during the blanking is that at the moment when the plate shears and breaks, the high pressure of the main cylinder of the hydraulic machine actuator suddenly disappears, and the liquid compression energy in the cylinder and the elastic deformation of the fuselage can be released suddenly. This process caused the hydraulic machine to shake strongly and the piping to vibrate, making the entire equipment very noisy.

Common shock-absorbers are divided into mechanical shock-absorbers and hydraulic shock-absorbers. Among them, the shock-absorber using spring energy absorption and the rubber shock-absorber energy absorption device belong to the mechanical shock-absorber, and the hydraulic energy absorption shock-absorber belongs to the hydraulic shock-absorber. At present, the back pressure method is mainly used for noise reduction in hydraulic presses. The basic principle is that when the plate breaks, a reverse force is provided by the reverse hydraulic cylinder to act on the slider, instead of the plate acting on the slider of the hydraulic machine during punching.

The load of the hydraulic machine enables the hydraulic machine to smoothly transition from the punching process load to the load of the reverse hydraulic cylinder, so that the hydraulic energy accumulated in the main hydraulic cylinder and the elastic deformation of the fuselage can be controlled and released, ensuring that there is no sudden loss of the hydraulic machine during work. The charge phenomenon eliminates the resulting shock and vibration.

Calculation of shock-absorber parameters

The height of 2000t hydraulic press is 500～2200mm, and the size of the worktable is 4000mm×1900mm. Among the main punching dies, the size of the side pillar blanking die is 3200mm×1170mm×820mm, the size of the large beam blanking die is 3 850mm×860mm×705mm, and the required punching force is about 11000kN. In order to ensure that the use of the blanking mold is not hindered after the shock-absorber is installed, four shock-absorber cylinders are installed on the left and right sides of the hydraulic machine base, and the nominal force of each shock-absorber cylinder is 2500kN.

According to the size of the hydraulic press table and the width of the mold, the maximum size of the outer diameter of the shock-absorber cylinder is 520mm. In combination with the adjustment amount and the wall thickness of the shock-absorber cylinder when the mold is installed, the inner diameter of the shock-absorber cylinder should not be greater than 360mm.

Calculated with an inner diameter of 360mm, the pressure area of the shock-absorber cylinder is 0.102 square meters. According to the pressure formula, the pressure of the shock-absorber cylinder can reach 24.5MPa. Use imported seals for sealing to prevent hydraulic leakage. According to the height of the mold, the minimum height of the shock-absorber cylinder is 700mm, the shock-absorber stroke is 50mm, the total adjustable height is 400mm, the fine adjustment height is 50mm, and the total adjustment range of the pressure of the shock-absorber is 4000kN ~ 10000kN.

Shock-absorber cylinder structure

The shock-absorber cylinder is composed of a cylinder body, a piston rod, a butterfly spring, a support plate, an adjustment screw, a cushion block, an upper fixed cushion, an oil tank, etc. The structure is shown in Figure 1, and the actual object is shown in Figure 2.

Each shock-absorber cylinder is equipped with an independent hydraulic oil tank. The hydraulic oil circulates back and forth in the hydraulic pipeline without power drive, which can reduce energy consumption and reduce the failure rate. In order not to hinder the use of other molds, the shock-absorber cylinder is connected to the hydraulic press working table with bolts, which has high flexibility and easy installation and disassembly.

The piston rod is processed into a thread form, and is equipped with an exhaust device, which can quickly exhaust the air in the cylinder to ensure stable pressure and smooth operation. The butterfly spring is installed in the cylinder body and guided by the guide rod, so that the butterfly spring has no deviation under vibration conditions, and the piston rod lifting movement is stable and reliable.

The adjusting screw is set in the piston rod, and the adjusting screw and the piston rod are in the form of a threaded screw structure. By rotating the adjusting screw, the height fine adjustment function is realized. A lock nut is provided on the height fine adjustment device. When the height is adjusted to an appropriate height, the lock nut is tightened to prevent loosening. When the adjustment height is greater than 50 mm, different numbers of pads can be placed on the end surface of the adjustment screw to meet the use requirements of molds of different heights. There is a positioning slot between each pad to prevent the pad from sliding down due to vibration.

Shock-absorber cylinder hydraulic system

The shock-absorber cylinder hydraulic system is installed on the pipeline between the oil tank and the shock-absorber cylinder, and is used to provide pressure to the shock-absorber cylinder. The hydraulic system consists of a one-way relief valve, joints and pipes. The one-way relief valve is provided with scale and pressure dial, which can conveniently set the pressure.

Application of shock-absorber

The shock-absorber is installed on the 2000t hydraulic machine. When the side pillar blanking mold is replaced by the large beam mold, only two pads need to be removed according to the height, and the height of the adjustment screw can be adjusted to perform blanking production. There is only slight noise during production, which greatly reduces the impact and vibration of the impact force on the equipment during punching.