In the design of hydraulic cylinder, first of all, we need to determine the piston diameter D and piston rod diameter D. to determine the piston diameter and piston rod diameter, we need to find the load of the hydraulic cylinder and carry out the force analysis; in the case of determining the force, we can roughly determine the piston diameter and piston rod diameter by selecting the appropriate liquid flow. Besides D and D, the structural parameters of hydraulic cylinder include piston stroke s, guiding distance h and oil port diameter D. The stroke of the hydraulic cylinder should be set according to the working needs. In order to simplify the manufacturing process and save the manufacturing cost, a series of standardized stroke size parameters should be adopted. In order to reduce the deviation between the piston rod and the cylinder shaft, the hydraulic cylinder should have a reasonable guide length.The end cover is divided into front cover and back cover. The front end cover seals the piston rod (plunger) cavity to guide, seal and prevent dust. The rear end cover is the closed end of the cylinder, which usually plays the role of connecting the hydraulic cylinder and other components.There are eight common connection modes between cylinder and end cover: pull rod type, flange type, welding type, internal thread type, external thread type, internal snap ring type, external snap ring type and steel wire retaining ring type. Welding type is only applicable to the connection between cylinder and end cover.Oil cylinder requiredThe cylinder is the main part of the hydraulic cylinder, sometimes the direct working part of the hydraulic cylinder (when the piston rod or plunger is fixed); it forms a sealing cavity with the end cover and the piston (plunger) to contain the pressure oil and drive the load to do work, so it has the requirements of strength, stiffness and sealing.Material selection of cylinderAnnealed cold drawn or hot rolled seamless steel tubes are widely used in cylinder billets. There are already semi-finished products for honing or finishing inner holes on the market. The seamless steel pipe only needs to be cut according to the required length. The materials are 20, 35, 45 steel and 27SiMn alloy steel. Because the mechanical properties of No. 20 steel are a little low, it can not be quenched and tempered, so it is rarely used. When welding cylinder and cylinder bottom, cylinder head, pipe joint or trunnion, 35 steel with good weldability is rough machined and then tempered. Generally, 45 steel is used and tempered to 241 ~ 285hb.