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Briefly describe the solution to the problem of low-speed crawling of the hydraulic cylinder
1. Low-speed crawling caused by the presence of gas in the rod cavity and rodless cavity of the hydraulic cylinder barrel can be achieved by repeatedly operating the hydraulic cylinder to achieve the purpose of exhausting. An exhaust device is installed in the pipeline or its two cavities to exhaust the gas when the hydraulic system is working.
2. For low-speed crawling caused by improper design clearance of the hydraulic cylinder, the sliding fit clearance between the piston and the cylinder block, the piston rod and the guide sleeve in the hydraulic cylinder can be correctly designed. The theoretical fit clearance is H9/N or H9/f8, and there are also H8/f8; according to the author's experience, its cylinder diameter and rod diameter are from small to large. If the fit clearance is designed according to this, for larger cylinder diameters (&ge ;200mm) and rod diameter (≥140mm), the gap appears to be too large. In the actual application process, the low-speed crawling phenomenon of this type of hydraulic cylinder occurs more often in hydraulic cylinders with smaller bore diameters. The matching gap of the sliding surface of this type of hydraulic cylinder is generally designed to be 0.05mm~0.15mm. From the actual comparison results, its low-speed crawling problem is obviously optimized. Therefore, it is recommended to use this method for large bore diameters.
3. Low-speed crawling caused by uneven friction of the internal guide elements. It is recommended to use metal as the guide support. If a non-metallic support ring is used, it is recommended to use a non-metallic support ring with good dimensional stability in oil. The main reason is that the thermal expansion coefficient should be small. In addition, for the thickness of the support ring, the dimensional tolerance and thickness uniformity must be strictly controlled.
4. For low-speed crawling of hydraulic cylinders caused by seal material problems, it is recommended that when the working conditions permit, it is recommended to use polytetrafluoroethylene as the sealing combination seal ring, such as commonly used Gley rings, Ster seals, etc.; if lip seals are selected, it is recommended that the material be a seal made of nitrile rubber or similar materials, which has better followability.
5. The impact of component machining accuracy. In the manufacturing process of the hydraulic cylinder, the machining accuracy of the inner wall of the cylinder and the piston rod surface should be strictly controlled, mainly geometric accuracy. Straightness is the key. In the processing technology, the processing of the piston rod surface is basically post-turn grinding, which ensures that straightness is not a big problem. However, for the processing of the inner wall of the cylinder, there are many processing methods, including boring-rolling and boring. - Honing, direct honing, etc. However, due to the gap in the basic level of materials compared with foreign countries, the pipe blank has poor straightness, uneven wall thickness, uneven hardness and other factors, which often directly affect the straightness of the cylinder inner wall after processing. Therefore, it is recommended to use boring - rolling, boring - honing processes. If direct honing, the straightness of the pipe blank must be increased first.
In addition to the above methods, if the cylinder wall thickness is allowed, the safety factor should be as large as possible to increase the cylinder wall thickness, mainly for oil cylinders used under high-pressure conditions to reduce cylinder deformation under oil pressure. The deformed cylinder will also cause the hydraulic cylinder to crawl at low speed.
2. For low-speed crawling caused by improper design clearance of the hydraulic cylinder, the sliding fit clearance between the piston and the cylinder block, the piston rod and the guide sleeve in the hydraulic cylinder can be correctly designed. The theoretical fit clearance is H9/N or H9/f8, and there are also H8/f8; according to the author's experience, its cylinder diameter and rod diameter are from small to large. If the fit clearance is designed according to this, for larger cylinder diameters (&ge ;200mm) and rod diameter (≥140mm), the gap appears to be too large. In the actual application process, the low-speed crawling phenomenon of this type of hydraulic cylinder occurs more often in hydraulic cylinders with smaller bore diameters. The matching gap of the sliding surface of this type of hydraulic cylinder is generally designed to be 0.05mm~0.15mm. From the actual comparison results, its low-speed crawling problem is obviously optimized. Therefore, it is recommended to use this method for large bore diameters.
3. Low-speed crawling caused by uneven friction of the internal guide elements. It is recommended to use metal as the guide support. If a non-metallic support ring is used, it is recommended to use a non-metallic support ring with good dimensional stability in oil. The main reason is that the thermal expansion coefficient should be small. In addition, for the thickness of the support ring, the dimensional tolerance and thickness uniformity must be strictly controlled.
4. For low-speed crawling of hydraulic cylinders caused by seal material problems, it is recommended that when the working conditions permit, it is recommended to use polytetrafluoroethylene as the sealing combination seal ring, such as commonly used Gley rings, Ster seals, etc.; if lip seals are selected, it is recommended that the material be a seal made of nitrile rubber or similar materials, which has better followability.
5. The impact of component machining accuracy. In the manufacturing process of the hydraulic cylinder, the machining accuracy of the inner wall of the cylinder and the piston rod surface should be strictly controlled, mainly geometric accuracy. Straightness is the key. In the processing technology, the processing of the piston rod surface is basically post-turn grinding, which ensures that straightness is not a big problem. However, for the processing of the inner wall of the cylinder, there are many processing methods, including boring-rolling and boring. - Honing, direct honing, etc. However, due to the gap in the basic level of materials compared with foreign countries, the pipe blank has poor straightness, uneven wall thickness, uneven hardness and other factors, which often directly affect the straightness of the cylinder inner wall after processing. Therefore, it is recommended to use boring - rolling, boring - honing processes. If direct honing, the straightness of the pipe blank must be increased first.
In addition to the above methods, if the cylinder wall thickness is allowed, the safety factor should be as large as possible to increase the cylinder wall thickness, mainly for oil cylinders used under high-pressure conditions to reduce cylinder deformation under oil pressure. The deformed cylinder will also cause the hydraulic cylinder to crawl at low speed.