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What are the failure modes of four – point contact slewing bearings?

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Four – point contact slewing bearings have various failure modes. Each failure mode seriously affects its performance and the operation of the equipment.

What is Four – Point Contact Slewing Bearing

A four – point contact slewing bearing is a type of bearing structure. It consists of components such as an inner ring, an outer ring, rolling elements, and a cage. Its uniqueness lies in that the rolling elements have four – point contact with the raceways of the inner and outer rings, enabling it to simultaneously withstand axial forces, radial forces, and tilting moments. This design gives the slewing bearing a high load – carrying capacity and rotational accuracy within a limited space. It is commonly used in construction machinery and large – scale equipment such as cranes, excavators, and wind turbines. It can achieve smooth rotational motion between components, adapt to complex working conditions, and improve the reliability and stability of the equipment.

Failure Modes of Four – Point Contact Slewing Bearings

Wear

– Raceway Wear: When a four – point contact slewing bearing is in operation, the steel balls continuously roll within the raceways. There is relative motion and contact pressure between them. After long – term operation, the surface of the raceway will gradually wear due to friction. The wear increases the surface roughness of the raceway, making the originally smooth raceway rough. This leads to an increase in the friction force between the steel balls and the raceway, and an increase in energy consumption during operation. At the same time, the dimensional accuracy of the raceway decreases, affecting the rotational accuracy of the slewing bearing and reducing the operating stability of the equipment. For example, in some frequently rotating robotic arms, raceway wear may cause a decrease in the positioning accuracy of the robotic arm, affecting its work quality.

– Cage Wear: The cage is used to separate the steel balls and guide them to roll correctly within the raceways. During the operation of the slewing bearing, there is a certain amount of relative motion and friction between the cage, the steel balls, and the inner and outer rings. If the material of the cage has insufficient wear resistance or the lubrication is poor, wear is likely to occur. After the cage is worn, its guiding and positioning function for the steel balls is weakened. The steel balls may become skewed and collide with each other, further aggravating the wear of the steel balls and the raceway. In severe cases, the steel balls may even come out of the raceway, causing the slewing bearing to fail.

Fatigue Spalling

– Raceway Fatigue Spalling: When a four – point contact slewing bearing is working, the surface of the raceway bears periodic contact stress. Over time, under the action of this alternating stress, the metal material on the surface of the raceway gradually fatigues. Initially, tiny cracks appear at the microscopic level on the surface of the raceway. These cracks will continue to expand as the number of operating cycles increases. When the cracks expand to a certain extent, the metal on the surface of the raceway will spall off, forming fatigue spalling pits. These spalling pits damage the surface integrity of the raceway, deteriorate the contact state between the steel balls and the raceway, cause vibration and noise during the operation of the slewing bearing, reduce the working performance of the equipment, and in severe cases, even affect the load – carrying capacity of the slewing bearing, resulting in the equipment being unable to operate normally.

– Steel Ball Fatigue Spalling: The steel balls also bear cyclic contact stress, and their surfaces are prone to fatigue spalling. Once spalling occurs on the surface of the steel ball, it will change the contact points and contact force distribution between the steel ball and the raceway, intensify the stress concentration in other parts, and accelerate the further damage of the steel ball and the raceway. Moreover, the spalled metal debris may enter the gap between the raceway and the steel ball, aggravating wear and scratching, and further shortening the service life of the slewing bearing.

Plastic Deformation

– Overload Plastic Deformation: When the load borne by a four – point contact slewing bearing exceeds the yield strength of its material, the metal on the surfaces of the raceway and the steel balls will undergo plastic deformation. This deformation usually manifests as pits or protrusions on the surface of the raceway, and the shape of the steel balls may also change. Plastic deformation destroys the original accuracy and geometric shape of the slewing bearing, increases the fit clearance between the steel balls and the raceway, and causes the slewing bearing to shake and become unstable during operation, seriously affecting the working accuracy and reliability of the equipment. For example, in some large – scale cranes, if the slewing bearing undergoes overload plastic deformation, it may cause the jib to shake significantly during rotation, endangering the safety of the hoisting operation.

– Impact Plastic Deformation: When the equipment starts, brakes, or is subjected to external impact loads, the four – point contact slewing bearing will bear a large instantaneous impact force. This impact force may cause local plastic deformation on the surfaces of the raceway and the steel balls. Although the action time of the impact load is short, if the impact force is large enough, it will still cause serious damage to the slewing bearing. Impact plastic deformation may form tiny pits or deformed areas on the surfaces of the raceway and the steel balls. These areas will become stress – concentration points during subsequent operation, accelerating the generation and expansion of fatigue cracks and reducing the service life of the slewing bearing.

Corrosion

– Chemical Corrosion: Four – point contact slewing bearings are usually exposed to various environments. When they come into contact with water vapor, oxygen, and other corrosive media in the air, a chemical reaction occurs on the metal surface, forming corrosion products. For example, slewing bearings made of steel are prone to oxidation reactions in a humid environment, producing rust. Corrosion gradually erodes the material on the metal surface, weakens the strength and wear resistance of the material, and reduces the performance of the slewing bearing. As the corrosion intensifies, the surface of the slewing bearing becomes rough and uneven, and may even develop pits, affecting the fit accuracy between the steel balls and the raceway, increasing the operating resistance of the slewing bearing, and consuming more energy.

– Electrochemical Corrosion: If there is an electrolyte solution in the environment where the slewing bearing is located and there is a potential difference between different metal components, a galvanic cell will be formed, triggering electrochemical corrosion. For example, when the inner and outer rings of the slewing bearing are made of different metal materials or there are unevenness in the surface treatment process, electrochemical corrosion is likely to occur under the action of the electrolyte solution. Electrochemical corrosion accelerates the local corrosion rate of metal components, forming corrosion pits and cracks, and seriously affecting the structural integrity and load – carrying capacity of the slewing bearing.

Fracture

– Raceway Fracture: Raceway fracture is a relatively serious failure mode. The reasons may include defects in the material itself, such as inclusions and pores inside. When subjected to loads, stress concentration is likely to occur at these defective locations, triggering cracks and their expansion. In addition, residual stress generated during the processing process, if not effectively eliminated, may also cause the raceway to crack during subsequent use. Moreover, overload or long – term fatigue can also cause cracks in the raceway, eventually leading to fracture. After the raceway fractures, the slewing bearing cannot normally bear the load, the equipment will stop running immediately, and it may even cause safety accidents.

– Steel Ball Fracture: If there are internal defects in the steel balls during the manufacturing process, such as uneven structure caused by improper forging technology or heat treatment defects, when they are subjected to large impact forces or cyclic stress during use, they may fracture. After the steel ball fractures, it will damage the load – bearing structure of the slewing bearing, change the load distribution borne by other steel balls, accelerate the damage of other components, and may also cause the equipment to vibrate violently and produce abnormal noise.

– Cage Fracture: The cage plays an important role in the slewing bearing. If there are improper installation situations, such as over – tightening or under – tightening during installation, the cage will bear additional stress during operation. In addition, when the slewing bearing is subjected to large external impact forces or interferes with other components, the cage is also easily damaged. After the cage fractures, the steel balls will lose their restraint and may collide with each other and scatter within the raceway, resulting in the complete failure of the slewing bearing.

Price of Four – Point Contact Slewing Bearings

Materials are a crucial factor. Using high – quality steel and special alloys can enhance strength and wear resistance. This increases the cost, and thus the price will be higher. For example, slewing drives made of materials containing special alloys are more expensive than those made of ordinary materials. Machining accuracy is also important. High – precision machining requires advanced equipment and technologies, which increases the cost, and as a result, the product price is naturally higher. The slewing drives used in precision equipment generally have high prices. The manufacturing process also affects prices. Advanced processes can optimize performance but also increase costs, thereby raising the selling price.

Supplier of Four – Point Contact Slewing Bearings

LDB bearing company has risen from obscurity to become well – known in the industry, relying on its dedication to quality and pursuit of innovation. The company is located in Luoyang, Henan Province, where the bearing industry is developed, enjoying the advantages of industrial resources. For example, its self – developed straight – tooth gear slewing drives have high precision and strong stability, greatly improving the operation accuracy and efficiency of industrial welding robots. With high – quality products and attentive services, it has won numerous praises and is bound to create more glories in the future!

How about the Load – Carrying Capacity of Four – Point Contact Slewing Bearings

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As an important mechanical component, four – point contact slewing bearings play a crucial role in many engineering fields. Their load – carrying capacity is an important indicator to measure their performance. They can withstand axial forces, radial forces, and tilting moments under different working conditions, providing reliable support for the stable operation of equipment.

What is Four – Point Contact Slewing Bearing

A four – point contact slewing bearing is a type of bearing structure. It consists of components such as an inner ring, an outer ring, rolling elements, and a cage. Its uniqueness lies in that the rolling elements have four – point contact with the raceways of the inner and outer rings, enabling it to simultaneously withstand axial forces, radial forces, and tilting moments. This design gives the slewing bearing a high load – carrying capacity and rotational accuracy within a limited space. It is commonly used in construction machinery and large – scale equipment such as cranes, excavators, and wind turbines. It can achieve smooth rotational motion between components, adapt to complex working conditions, and improve the reliability and stability of the equipment.

Axial Load – Carrying Capacity

The axial load – carrying capacity of a four – point contact slewing bearing is one of its significant advantages. Structurally, the steel balls have four – point contact with the arc – shaped raceways of the inner and outer rings. This design allows the axial force to be evenly distributed among each contact point. When subjected to an axial load, each steel ball can effectively share the force, thus enhancing the overall axial load – carrying capacity.

Generally, the axial load – carrying capacity of a small – sized four – point contact slewing bearing can reach several tens of kilonewtons. For example, in some small industrial robots, the axial load – carrying capacity of the four – point contact slewing bearings used may be around 30 – 50 kN, which can meet the axial force requirements generated during the movement of the robot arm. For large – scale construction machinery, such as large – scale tower cranes, the axial load – carrying capacity of the four – point contact slewing bearings used can reach several thousand kilonewtons or even higher. In some super – large tower cranes, the axial load – carrying capacity of the slewing bearings may exceed 5000 kN to withstand the huge axial forces generated during the hoisting and rotation of the jib and heavy objects.

Radial Load – Carrying Capacity

Although the four – point contact slewing bearing is not a specialized radial bearing, it still has a certain radial load – carrying capacity. In actual work, equipment often generates axial forces, radial forces, and tilting moments simultaneously. The four – point contact slewing bearing needs to withstand axial forces and tilting moments while also accommodating a certain radial force.

Its radial load – carrying capacity mainly depends on the contact angle between the steel balls and the raceways and the fitting accuracy. When the contact angle between the steel balls and the raceways is reasonable and the manufacturing accuracy is high, the radial load – carrying capacity can be improved to a certain extent. However, compared with specialized radial bearings, the radial load – carrying capacity of four – point contact slewing bearings is relatively weak. For example, in some small rotating worktables, the radial load – carrying capacity of the four – point contact slewing bearings used may be around 10 – 20 kN, while that of specialized radial bearings of the same specification may reach 30 – 50 kN. But in most practical applications, the radial load – carrying capacity of four – point contact slewing bearings can usually meet the radial force requirements generated by the equipment under normal working conditions.

Tilting Moment Load – Carrying Capacity

Four – point contact slewing bearings perform excellently in withstanding tilting moments. When the equipment is in operation, tilting moments are generated due to various factors (such as eccentric loads, wind forces, etc.), which puts forward high requirements for the anti – tilting ability of the slewing bearing.

Through its special structural design, the four – point contact slewing bearing can convert the tilting moment into the pressure between the steel balls and the raceways. When a tilting moment acts, the steel balls on one side are subjected to greater pressure, while those on the other side are under relatively less pressure. By changing the distribution of this pressure, it can resist the tilting moment. Some large – scale four – point contact slewing bearings can withstand tilting moments of up to tens of thousands of kilonewton – meters. For example, in large – scale port cranes, due to their large working radius and high lifting capacity, huge tilting moments are generated during the operation. The four – point contact slewing bearings used can withstand tilting moments of over 50000 kN·m, ensuring the stable operation of the crane under various working conditions.

Factors Affecting the Load – Carrying Capacity

The load – carrying capacity of four – point contact slewing bearings is affected by multiple factors. Firstly, material properties are one of the key factors. High – quality bearing steels, such as GCr15SiMn steel, have high strength, high hardness, and good wear resistance, which can improve the load – carrying capacity and service life of the slewing bearing. Secondly, manufacturing accuracy is also crucial. The machining accuracy of the raceways, the dimensional accuracy, and the roundness of the steel balls directly affect the contact state between the steel balls and the raceways and the even distribution of forces. High – precision manufacturing processes can make the contact between the steel balls and the raceways more uniform when the slewing bearing is under load, thereby improving the load – carrying capacity. In addition, parameters such as the shape and size of the raceways, and the number and diameter of the steel balls also affect the load – carrying capacity. Reasonably designing the shape and size of the raceways and selecting the appropriate number and diameter of the steel balls can optimize the load – carrying performance of the slewing bearing.

Calculation and Selection of the Load – Carrying Capacity

In practical applications, accurately calculating and reasonably selecting the load – carrying capacity of four – point contact slewing bearings is of great importance. Engineers need to perform precise calculations based on the specific working conditions of the equipment, including parameters such as the maximum axial force, radial force, tilting moment, rotational speed, and working temperature, in combination with relevant standards and calculation formulas for slewing bearings. At the same time, a certain safety factor needs to be considered to ensure that the slewing bearing can work safely and reliably during long – term operation. When selecting a slewing bearing, based on the calculation results, refer to the product samples and technical materials provided by slewing bearing manufacturers to select the appropriate specifications and models to meet the load – carrying capacity requirements of the equipment.

Price of Four – Point Contact Slewing Bearings

Materials are a crucial factor. Using high – quality steel and special alloys can enhance strength and wear resistance, increase costs, and thus lead to higher prices. For example, slewing drives made of materials containing special alloys are more expensive than those made of ordinary materials. Machining accuracy is also important. High – precision machining requires advanced equipment and technologies, which increases costs, and as a result, the product prices are higher. The slewing drives used in precision equipment generally have high prices. The manufacturing process also affects prices. Advanced processes can optimize performance but also increase costs, thereby raising the selling price.

Supplier of Four – Point Contact Slewing Bearings

LDB bearing company has risen from obscurity to become well – known in the industry, relying on its dedication to quality and pursuit of innovation. The company is located in Luoyang, Henan Province, where the bearing industry is developed, enjoying the advantages of industrial resources. For example, its self – developed straight – tooth gear slewing drives have high precision and strong stability, greatly improving the operation accuracy and efficiency of industrial welding robots. With high – quality products and attentive services, it has won numerous praises and is bound to create more glories in the future!