The design content of hydraulic cylinders of different types and structures is different. Since there are often inherent links between various parameters, there are no hard and fast rules for the design steps of hydraulic cylinders.
Under normal circumstances, the design procedures and steps should be flexibly selected according to the various materials and conditions that have been mastered, and repeated deliberation and calculations should be repeated until the design principles are met and satisfactory results are obtained.
General design work can refer to the following steps:
Step 1. Master the original data and design basis, including:
(1) The purpose and working conditions of the host;
(2) The structural characteristics, load conditions, stroke size and movement requirements of the working mechanism;
(3) The selected working pressure and flow rate of the hydraulic system;
(4) The actual situation of materials, accessories and processing technology;
(5) Relevant national standards and technical specifications, etc.
Step 2. According to the action requirements of the main engine in the design basis, carry out the force analysis of the hydraulic cylinder, and select the type of the hydraulic cylinder, the structure of each part, and the installation method.
Step 3. Determine the law of load change of the hydraulic cylinder at each stage of the stroke and the power value that must be provided according to the external load force that the hydraulic cylinder can withstand (including gravity, external mechanism movement friction, inertial force, and working load, etc.) Relevant technical data.
Step 4. Determine the end face area of the piston and calculate the diameter of the piston (that is, the diameter of the cylinder bore) and the outer diameter of the cylinder according to the working load of the hydraulic cylinder and the selected rated (working) pressure.
Step 5. Determine the diameter of the piston rod according to the ratio of the cylinder diameter to the moving speed or the allowable stress of the working load and the material.
Step 6. Determine the pressure and flow rate of the hydraulic pump according to the movement speed, work output and piston diameter.
Step 7. Select the structure of the cylinder head, and calculate the thickness and connection strength of the cylinder head and cylinder tube.
Step 8. Determine the maximum working length of the hydraulic cylinder according to the working stroke requirements. Generally, the maximum working length should not be less than the diameter of the piston rod. As the piston rod is slender, calculation of longitudinal bending strength, stiffness and stability of hydraulic cylinder should be carried out.
Step 9. Design devices for guiding, sealing, dustproofing, exhausting and buffering.
Step 10. Draw assembly drawings and parts drawings, and prepare technical documents.
Step 11. Verify all design calculation data, modify and supplement.
The design content of the hydraulic cylinder is not static. Depending on the specific situation, some content can be omitted or added. The design process may need to be modified repeatedly to get the correct and reasonable design results. The correct design and use of a hydraulic cylinder directly affect its performance. In this regard, problems such as improper installation of the hydraulic cylinder, unbalanced load on the piston rod, sagging of the hydraulic cylinder or piston, and instability of the pressure rod of the piston rod are often encountered. Therefore, when designing hydraulic cylinders, consideration must be given to the type selection, parameter calculation, structural design and installation of the hydraulic cylinder to avoid the above problems as much as possible.
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