Bearing knowledge

Precision bearing standards: High-precision bearings generally refer to bearings with an accuracy grade of P5 and above, mainly high-speed and high-precision bearings. As high-value-added functional components, high-precision bearings are mainly used for CNC machine tools, test and inspection equipment, military equipment, ball screw support, Sendzimir mills and other mechanical products. Taking the machine tool industry, the representative market of medium and large-scale high-precision bearings, as an example, high-precision bearings are mainly arranged in key parts such as machine tool spindle, ball screw pair and transmission shaft, which have a direct impact on the accuracy of the host. Bearing accuracy is generally divided into P0, P6, P5, P4, P2 grades and special SP, UP grades according to dimensional accuracy and rotational accuracy from low to high. Precision machine tool spindle bearings are generally P5 grade and above, and CNC machine tools and machining centers are For P4 level and above. Machine tool bearings are mostly matched with deep groove ball bearings, single-row and double-row cylindrical roller bearings, bidirectional thrust ball bearings, angular contact ball bearings or their matching groups, tapered roller bearings and thrust ball bearings. Section 1 Basic knowledge of rolling bearings A rolling bearing developed on the basis of sliding bearings, its working principle is to replace sliding friction with rolling friction. Strong, standardized, and highly serialized mechanical basic parts. Due to the different working conditions of various machines, various requirements are put forward for rolling bearings in terms of load capacity, structure and performance. For this reason, rolling bearings require various structures. However, the most basic structure is composed of inner ring, outer ring, rolling elements and cage. The functions of various parts in the bearing are as follows: for radial bearings, the inner ring is usually tightly fitted with the shaft and runs together with the shaft, and the outer ring is usually in transition fit with the bearing seat or the hole of the mechanical housing to play a supporting role. However, in some occasions, the outer ring also operates, the inner ring is fixed to play a supporting role, or both the inner ring and the outer ring operate at the same time. For thrust bearings, the shaft washer that is tightly fitted with the shaft and moves together is called the seat washer that is in transition fit with the bearing seat or the hole of the mechanical housing and plays a supporting role. The rolling elements (steel balls, rollers or needle rollers) are usually evenly arranged in the bearing between the two rings for rolling motion by means of a cage. Its shape, size and quantity directly affect the load capacity and performance of the bearing. In addition to evenly separating the rolling elements, the cage can also guide the rolling elements to rotate and improve the internal lubrication performance of the bearing. 1. Bearing maintenance In order to maintain the original performance of the bearing in a good state for as long as possible, maintenance and overhaul are required to prevent accidents before they occur, ensure the reliability of operation, and improve productivity and economy. Maintenance should preferably be carried out on a regular basis according to the operating standards corresponding to the operating conditions of the machine. The contents include the inspection of the vulgar state of the glaze, replenishment or replacement of lubricants, and regular disassembly. As maintenance items during operation, there are the rotational noise, vibration, temperature, and the state of the lubricant of the bearing. 2. Overhaul of bearing Cleaning of bearing: When disassembling the bearing for overhaul, first record the appearance of the bearing, confirm the residual amount of lubricant, and wash the bearing after sampling the lubricant for inspection. As the cleaning agent, cleaning agent and kerosene are generally used. The cleaning of the dismantled bearing is divided into coarse cleaning and fine cleaning, which are placed in the container respectively, and the bottom of the metal mesh is placed first, so that the bearing does not directly contact the dirt of the container. During rough cleaning, if the bearing is rotated with dirt, it will damage the rolling surface of the bearing, so be careful. In the rough cleaning oil, use a brush to remove grease and adhesions. After it is roughly clean, transfer to the fine cleaning. Fine cleaning is to carefully clean the bearing while rotating in the cleaning oil. In addition, the cleaning oil should always be kept clean. Bearing maintenance and judgment: In order to judge whether the disassembled bearing can be used, it should be checked after the bearing is cleaned. Check the raceway surface, rolling surface, and mating surface of the ridges ⒈3 for damage and abnormality. For non-separable small ball bearings, hold the inner ring horizontally with one hand, and rotate the outer ring to check for smoothness. For separable bearings such as tapered roller bearings, the rolling elements and the raceway surface of the outer ring can be inspected separately. Because large bearings cannot be rotated by hand, pay attention to checking the rolling element structure.