The hydraulic shearing machine has many advantages. Such as high speed, high shearing force, high efficiency, and protection against overload when cutting steel plates. When cutting the steel plate, the steel plate needs to be fixed. So there will be a row in front of the scissors. Usually, dozens of devices called presser feet, which are used to fix the steel plate (workpiece). It ensures the cutting size and prevents the steel plate from flying out.

Working principle of sheet pressing cylinder

As shown in Figure 1, in the natural state of the presser foot. The piston rod moves upward and retracts under the action of the spring force of the compression spring. When hydraulic oil is introduced into the upper cavity of the piston rod. The piston rod overcomes the spring force under the hydraulic pressure movement. Thereby pressing the steel plate (workpiece), to achieve a fixed shear of the workpiece. It should be noted that the number of the presser foot in the lateral direction (scissors) is several. Therefore, once the part leaks oil, it will cause serious pollution to the workpiece. Usually, the steel plate workpiece needs to be painted, which will adversely affect the adhesion of the paint. So This part must be sealed and reliable.

The structure design of the sheet pressing cylinder

As shown in Figure 2, it’s the cross-section of the designed sheet pressing cylinder.

The seal between the sheet pressing cylinder and the frame

The sealing between the sheet pressing cylinder and the frame is 46 × 3.0 outside the O-ring. And the extrusion gap is 3.0-2.6 = 0.4 mm, which is a static seal.

Piston rod main seal design

The piston rod part dynamic seal uses 2 UN25 × 33 × 5 seal rings, the material is polyurethane. And most of the structures are single seals, so this part is prone to oil leakage. An additional seal is designed here, and the material is also made of good wear resistance. Polyurethane material with greater hardness achieves a long seal life.

Guide belt design

A guide belt of 6 × 2.5 is designed. When the workpiece has lateral force, the guide belt can bear radial force, protect the piston rod and seal ring. And prevent the piston rod from scratching and causing oil leakage.

Conclusion

After the above-targeted theory combined with actual calculations, after improved design, it is used in the hydraulic shearing machine and has achieved a significant improvement effect. The life of the seal of the sheet pressing cylinder can reach 3 years or more, achieving the goal of long life, improving the surface quality of the steel plate workpiece, and causing no oil pollution to the subsequent process, which is worthy of popularization and application by peers.