The function and importance of the bearing cage.

Aug 30, 2024

The bearing cage, also known as the bearing retainer, is a vital component of the bearing structure.

Basic functions and roles

The main function of the bearing cage is to wrap and isolate the rolling elements (such as steel balls or rollers) to ensure that they can move in an orderly and stable manner inside the bearing. Specifically, the role of the cage can be summarized as follows:

Maintaining the spacing between rolling elements: The cage's main function is to maintain the rolling elements at an appropriate distance, preventing them from contacting each other and reducing friction and wear. This spacing helps to reduce the heat and noise generated by direct contact between the rolling elements and improves the operating efficiency and service life of the bearing.

Evenly distribute the load: By guiding the rolling elements to be evenly distributed in the rolling bearing, the cage can ensure that the load borne by the bearing is evenly distributed. It helps to reduce local stress and improve the overall load-bearing capacity and stability of the bearing.

Improve rolling conditions: In the unloaded area, the cage can guide the rolling elements to make their movement trajectory smoother, thereby improving the rolling conditions of the bearing. This guiding effect helps to reduce collisions and sliding between rolling elements and prevent damaging sliding phenomena.

Providing lubrication space: The design of the cage usually takes into account the lubrication needs, providing enough space for the lubricant to ensure that the rolling elements can be fully lubricated. It helps to reduce the friction coefficient, reduce heat generation, and extend the service life of the bearing.

Design considerations

When creating a bearing cage, it is essential to consider multiple factors to ensure that it meets the bearing's operational requirements. These design considerations include:

Structural strength: The cage needs to withstand various forces and stresses generated by the movement of the rolling elements, including friction, strain, and inertia. Therefore, the structure of the cage must be strong enough to ensure that it will not break or deform under extreme working conditions.

Geometry: The geometry of the cage has an important impact on its performance. Reasonable shape design can ensure that the rolling elements are evenly distributed in the bearing and reduce collisions and friction between each other. At the same time, the shape design also needs to consider the flow and distribution of the lubricant to ensure that the bearing is fully lubricated.

Material selection: The material of the cage has a decisive influence on its performance and service life. Commonly used cage materials include steel, non-ferrous metals (such as brass, aluminum alloys, etc.), and non-metals (such as polymers, etc.). These materials have their advantages and disadvantages and should be chosen based on specific application scenarios and requirements.

Manufacturing process: The manufacturing process also has an important impact on the quality and performance of the cage. Common manufacturing processes include stamping, die casting, plastic casting, etc. Different materials and shape requirements dictate suitable manufacturing processes, which must be selected and optimized based on specific circumstances.

Material selection

The material selection of bearing cages is a complex process that requires comprehensive consideration of multiple factors. The following are several common materials and their characteristics:

Steel cages: Steel cages are widely used due to their high strength, high toughness, and good processing performance. Commonly used steels include low-carbon steel, stainless steel, etc. These materials can withstand large stress and impact loads and have good wear resistance and corrosion resistance. However, the weight of steel cages is relatively large, which may affect the rotational inertia and energy consumption of the bearing.

Non-ferrous metal cages: Non-ferrous metal cages, such as brass and aluminum alloys, have low density, excellent thermal conductivity, and outstanding corrosion resistance. Cages made of these materials can reduce the overall weight of the bearing and reduce rotational inertia and energy consumption. At the same time, the thermal conductivity of non-ferrous metals helps to quickly dissipate the heat generated inside the bearing and improve the heat dissipation performance of the bearing. However, the strength and hardness of non-ferrous metals are relatively low and may not be suitable for some high-load and high-speed application scenarios.

Non-metallic cages: Non-metallic cages such as polymers and their composite materials (such as nylon, phenolic tape, polytetrafluoroethylene, etc.) have the advantages of lightweight, good elasticity, impact resistance, acid resistance, and corrosion resistance. Cages made of these materials can still maintain good motion characteristics under conditions of lack of lubricant, ensuring that the bearing continues to run for some time without damage. In addition, the sliding properties of non-metallic materials are excellent, which helps to reduce the heating and wear of the bearing. However, the performance of non-metallic cages in high-temperature environments may be limited, and their manufacturing process is relatively complex.

Application scenarios and performance.

The performance of bearing cages in different application scenarios has its characteristics. The following are some typical application scenarios and their performance:

High-speed rotation application: In high-speed rotation application scenarios, the cage needs to withstand huge centrifugal force and inertial force. At this time, it is necessary to select materials with high strength, lightweight, and good wear resistance to manufacture the cage to ensure the stable operation of the bearing. At the same time, the design of the cage also needs to consider reducing the impact of wind resistance and vibration on bearing performance.

Heavy-load application: In heavy-load mechanical equipment, such as heavy trucks, excavators, mining machinery, etc., bearings need to withstand huge radial and axial loads. At this time, the bearing cage needs to have sufficient strength and rigidity to support the rolling elements and prevent them from deformation or damage due to overload. The cages for heavy-load applications are usually made of high-strength steel or cast iron materials, and their load-bearing capacity is improved by strengthening the structural design. In addition, the design of the cage also needs to consider the distribution of rolling elements and load balance to ensure that the bearing can still maintain stable operation under heavy load conditions.

High-precision application: In mechanical equipment that requires high-precision positioning and rotation accuracy, such as precision machine tools, aerospace equipment, medical equipment, etc., the performance requirements of bearings are extremely high. At this time, the role of the bearing cage is not only to support the rolling elements but also to ensure that the rolling elements can achieve high-precision movement and positioning inside the bearing. The cages for high-precision applications are usually made of high-precision processing technology and high-quality materials to ensure that their geometric shape and dimensional accuracy meet the design requirements. At the same time, the design of the cage must also consider reducing friction and wear between rolling elements to improve the accuracy and life of the bearing.