What are the benefits of pre-tensioning for bearings?

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Six key aspects of bearing clearance: 1. The size of the clearance during operation (referred to as operating clearance) affects properties such as the rolling fatigue life, temperature rise, noise, and vibration of the bearing. 2. When measuring the bearing clearance, a specified measurement load is generally applied to the bearing in order to obtain stable measurement values. Therefore, the obtained measurement value is larger than the true clearance (referred to as the theoretical clearance), that is, it includes the elastic deformation caused by the measurement load. For roller bearings, this elastic deformation is small and can be ignored. 3. The internal clearance of the bearing before installation is generally expressed in terms of the theoretical clearance. 4. The clearance obtained by subtracting from the theoretical clearance the amount of expansion or contraction of the rings due to the interference fit when the bearing is installed on the shaft or in the housing is referred to as the \"installation clearance\". The clearance that takes into account the dimensional changes caused by temperature differences inside the bearing when added to or subtracted from the installed clearance is called the \"effective clearance\". 5. The bearing is equipped with a clearance when it is subjected to certain mechanical loads; this clearance, which is the effective clearance plus the elastic deformation caused by the bearing load, is referred to as the \"operating clearance\". 6. When the operating clearance is slightly negative, the bearing has the longest fatigue life; however, as the negative clearance increases, the fatigue life decreases significantly. Therefore, when selecting the clearance of a bearing, it is generally advisable to set the operating clearance to zero or slightly positive. Furthermore, when it is necessary to increase the stiffness of the bearing or reduce noise, the operating clearance should be made more negative; whereas when the bearing temperature rises significantly, the operating clearance should be made more positive, and so on. A specific analysis based on the operating conditions is also required. What are the benefits of preloading for bearings? What is bearing preloading? Generally, rolling bearings have a certain amount of play under operating conditions. However, to achieve a specific purpose, when configuring bearings, certain adjustment methods are used to apply a certain internal load to the bearings so that they can be used in a state of negative clearance; this method of use is known as preloading. What are the benefits of pre-tensioning for bearings? For rolling bearings, appropriate preloading can offer the following benefits: 1. Improve rotational accuracy. After bearing preloading, the internal clearance is eliminated; each rolling element is subjected to a certain preload, supporting the rings from all directions. This improves rotational accuracy and enables the shaft to be accurately positioned axially and radially, thereby enhancing the shaft’s rotational precision – as in the case of machine tool spindle bearings and measuring instruments. 2. Improve stiffness. The contact between the rolling elements and the raceways is elastic; therefore, the rolling elements can be regarded as springs. Bearings with play are supported by only a few springs in the direction of the applied force. The pre-tensioned bearing is supported by springs in all directions and has a certain amount of pre-load; the number of rolling elements that bear the load is greater than that in the relaxed state, thereby improving stiffness. In ball bearings, the relationship between the contact deformation of the balls and the raceways and the load is nonlinear; as the preload increases, the contact stiffness rises. 3. Extend the lifespan of the bearings. After pre-tensioning, the number of loaded rolling elements increases, the load on each rolling element decreases, and the load can be distributed more evenly among them, thereby extending the lifespan of the bearing. 4. Improve the damping of the bearing and reduce noise. Pre-tensioning creates a stable oil film between the rolling elements and the raceways, increasing the damping between them; this can improve the dynamic properties of the support structure and reduce noise. 5. Improve the dynamic performance of angular contact ball bearings. In high-speed rotating angular contact ball bearings, appropriate preloading can prevent the steel balls from undergoing gyroscopic rotation, prevent or reduce the orbital sliding of the steel balls, and also control their spin sliding. 6. Suppress vibration patterns and frictional wear. Spherical surface bearings are actually a variant of deep groove ball bearings; they are characterized by a spherical surface on the outer diameter of their outer ring, which allows them to fit into the corresponding concave spherical surface of the bearing housing, thereby serving a self-aligning function. Spherical bearings are primarily used to withstand combined radial and axial loads, with radial loads being the dominant type; they are generally not suitable for bearing axial loads alone. Used for vibration-free machining in machine tools for low-roughness processing, or in mechanisms that require friction wear control due to frequent starting and stopping. 7. Control the slippage of the rolling elements’ revolution and rotation. Sleeved external spherical bearings possess a certain degree of self-aligning capability in their design; they are easy to install, and come equipped with a dual-layer sealing system that allows them to operate in harsh environments. Bearing housings are generally manufactured by casting. Bearing units are high-precision component products composed of grease-sealed deep groove ball bearings and bearing housings of various shapes. The bearing assembly can be directly mounted to the main body of the mechanical device using several bolts. It features self-aligning capabilities and allows for the replenishment of lubricating grease, making it a product that is very easy to install and use. Such as radial thrust ball bearings used in high-frequency motors and cylindrical roller bearings used in jet engines, etc. 8. Compensate for wear during operation. During operation, bearings may experience an increase in clearance due to wear, and this can be compensated for through preloading.