What steps should be followed when designing a hydraulic cylinder?

Firstly, the wall thickness design of the hydraulic cylinder depends on the tensile strength of the material, the working pressure requirements, the piston stroke, etc. Generally, hydraulic cylinders in the north use grade 35, with large flow, low pressure, thin walls, and large pistons. In the south, grade 45 thick-walled high-pressure cylinders and American-style structural designs are mainly used. Gas trapped inside the hydraulic cylinder causes slow crawling. This can be achieved by repeatedly operating the hydraulic cylinder to expel the gas. In necessary cases, exhaust devices can be set in the pipelines or on the two chambers of the hydraulic cylinder during the operation of the hydraulic system to expel the gas.

Selection of hydraulic cylinder guide supports

For the low-speed crawling caused by uneven friction of the internal guide elements in the hydraulic cylinder, it is recommended to prioritize the use of metals as the guide supports. If non-metal support rings are used, it is advisable to select non-metal support rings with good dimensional stability in the oil, especially with a small thermal expansion coefficient. Additionally, the thickness of the support ring must be strictly controlled in terms of dimensional tolerance and uniformity of thickness.

Selection of sealing rings

For the low-speed crawling problem of the hydraulic cylinder caused by the material of the sealing element, it is recommended to prioritize the use of a combined sealing ring with polytetrafluoroethylene as the sealing material; if a lip seal is selected, it is recommended to use nitrile rubber or similar materials for the sealing element, as these materials have better followability.

Selection of hydraulic cylinder types and structural forms

Choose the type and structural form of the hydraulic cylinder based on the action requirements of the main machine; determine the variation pattern of the load on the hydraulic cylinder at each stage of its stroke and the required power value based on the external load forces it bears, such as gravity, external mechanism motion friction force, inertia force and working load.

Selection of the internal structure of the hydraulic cylinder

Based on the working load of the hydraulic cylinder and the selected working pressure of the oil, determine the diameters of the piston and the piston rod; based on the movement speed of the hydraulic cylinder, the diameter of the piston and the piston rod, determine the flow rate of the hydraulic pump; select the material of the cylinder barrel, calculate the outer diameter; select the structural form of the cylinder cover, calculate the connection strength between the cylinder cover and the cylinder barrel. Finally, according to the requirements of the working stroke, determine the working length of the hydraulic cylinder and the diameter of the piston rod. Generally speaking, the working length is greater than the diameter of the piston rod. Due to the slender nature of the piston rod, longitudinal bending strength verification and stability calculation of the hydraulic cylinder should be conducted. If necessary, design buffer, exhaust and dust-proof devices.