Cutting Machine Hydraulic Cylinder Crawling Low Speed Problem

- Feb 24, 2021-

1. The hydraulic cylinder of the hydraulic cutting machine has a rod cavity and a rod-free cavity containing gas and produces a low speed creep. The purpose of exhaust can be achieved by repeatedly running the hydraulic cylinder.




2. Low speed crawling caused by improper clearance of hydraulic cylinder of hydraulic cutting machine can correctly design sliding clearance between piston and cylinder, piston rod and guide sleeve inside hydraulic cylinder. In theory, the clearance is H9 / N or H9 / F8, and there are H8 / F8. According to the experience of this author, the cylinder diameter and rod diameter of the hydraulic cylinder from small to large, such as this to design the fit clearance, for larger cylinder diameter (≥? 200 mm) and stem diameter (140 mm) or higher fit clearance gap is too big, actually should process, this kind of hydraulic cylinder at low speed crawl phenomenon appear smaller diameter hydraulic cylinder, such hydraulic cylinder fitting clearance of the slip plane with the general design abroad ∽ 0.15 mm and 0.05 mm from the point of the results of actual comparison, the hydraulic cylinder of low-speed crawling problem obviously improved. Therefore, it is recommended to choose this method for the large diameter hydraulic cylinder




Guide element within three, cutting machine, hydraulic cylinder friction uneven produced by low speed crawl, preferred with metal as the guide, such as QT500-7, ZQAL9-4, such as using non-metallic support ring, choose the dimensional stability in oil good advice non-metallic support ring, especially the thermal expansion coefficient should be small, in addition to the thickness of the support ring, must strictly control the uniformity of size tolerance and thickness.




4. For the low speed crawling of the hydraulic cylinder of the cutting machine caused by the material problem of the sealing parts, it is suggested that the combined sealing ring with PTFE as the seal should be preferred under the condition that the working conditions permit, such as the commonly used greyring and steseal, etc.; If the lip sealing is selected, it is suggested that the sealing material should be NBR or similar material, which has good follow-along performance.




5, the influence of the precision parts processing, in the manufacturing process of hydraulic cylinder hydraulic cutting machine should strictly control the cylinder wall and piston rod surface machining accuracy, especially the geometric accuracy, especially the straightness is the key, in the domestic processing technology, processing on the surface of the piston rod is basically a car after grinding, ensure straightness problem is not big, but for the inner wall of the cylinder block processing, the processing method are many, boring, rolling, boring - direct honing honing, etc, but due to the basic level of domestic materials, compared with foreign gap pipe blank straightness error, uneven uneven thickness, hardness and other factors, It often directly affects the straightness of cylinder inner wall after processing, so it is suggested to adopt boring - rolling, boring - honing technology, such as direct honing, it must first improve the straightness of pipe blank.