What are the accuracy requirements of the inner and outer ring raceways of double row ball slewing rings?

What is double row ball slewing ring

The double-row ball slewing ring is composed of an inner/outer ring, two rows of steel balls and a cage, and the relative rotation is achieved by rolling the steel balls in the raceway, which can withstand axial force, radial force and overturning moment. Its advantages lie in the high load-bearing capacity brought by the double-row structure, high-precision machining to ensure operational accuracy, high-quality materials and design to extend life, and easy installation. Widely used in construction machinery (such as excavators, cranes), wind power generation, port machinery and other fields, there are strict requirements for materials, heat treatment and processing accuracy during manufacturing, and the quality is ensured through testing, which is the core component of equipment rotary movement.

Features of double row ball slewing rings

A double-row ball slewing ring is a mechanical component used to withstand large axial forces, radial forces and overturning moments, with the following characteristics:

Strong bearing capacity: The double row ball slewing ring has two rows of steel balls, which can withstand axial force, radial force and overturning moment at the same time. Compared with the single-row ball slewing ring, its bearing capacity is greatly improved, which can meet the force requirements of large machinery and equipment under complex working conditions, such as large cranes, shield machines and other equipment, which can withstand the huge load generated by lifting heavy objects and various forces during equipment operation.

High Rotation Accuracy: Through precise machining technology and assembly technology, double row ball slewing rings can ensure high rotation accuracy. The matching accuracy of the raceway and the steel ball is high, which can make the equipment stable during rotation and reduce vibration and swing, which is very important for some equipment that requires high precision, such as radar antennas and astronomical telescopes, to ensure that it accurately points to the target and improves the working performance.

Good rigidity: The structural design of the double row ball makes it have good rigidity. When bearing load, it can effectively resist deformation and maintain the stability of the structure. This helps to improve the overall strength and reliability of the equipment, and prolong the service life of the equipment, especially in some heavy-duty and high-impact working environments, such as mining machinery, port machinery, etc., which can better adapt to harsh working conditions.

Stable operation: the steel ball rolls in the raceway, the friction resistance is small, and the distribution of the double row ball makes the load evenly distributed, so as to ensure the stability of the slewing ring in the running process. The equipment runs smoothly when rotating, reducing noise and vibration, improving the quality of the operator's working environment, while also reducing wear and impact on other parts of the equipment.

Easy installation: Double row ball slewing rings are usually designed with standardized mounting interfaces and dimensions for easy connection and installation with other parts of the equipment. Its structure is relatively compact, occupies a small space, and can achieve a large bearing capacity and rotation function in a limited space, which provides convenience for the design and manufacture of equipment.

Low maintenance cost: Due to its simple structure and reliable operation, the maintenance of double row ball slewing rings is relatively easy. It only needs to regularly check the lubrication, sealing performance and wear of components, lubricate and replace worn parts in time, which reduces the maintenance cost and downtime of the equipment and improves the efficiency of the equipment.

What are the accuracy requirements of the inner and outer ring raceways of double row ball slewing rings?

The accuracy requirements of the inner and outer ring raceways of the double row ball slewing ring usually include the following aspects:

Dimensional accuracy

Diameter tolerance: The inner and outer diameter dimensional tolerances of raceways are usually controlled within a small range, generally between ±0.05mm and ±0.1mm, and the specific values are determined according to the specifications and use requirements of the slewing ring. For example, for some slewing rings for industrial robots with high precision requirements, the diameter tolerance may be controlled within ±0.05mm to ensure the accuracy of the fit with other components.

Width tolerance: There are also strict tolerances for raceway widths, generally between ±0.1mm and ±0.2mm. If the raceway width tolerance is too large, it may cause the movement of the steel ball in the raceway to be unstable, affecting the bearing capacity and rotation accuracy of the slewing ring.

Shape accuracy

Roundness: The roundness error of the raceway is usually required to be controlled between 0.01mm and 0.03mm. Poor roundness will make the contact stress distribution between the steel ball and the raceway uneven, accelerate the wear of the raceway and the steel ball, and reduce the service life of the slewing ring.

Condelricity: For cylindrical raceways, the cylindricity requirement is generally between 0.02mm and 0.05mm. Excessive cylindricity error may lead to the deviation of the steel ball in the raceway, which affects the rotation accuracy and stability of the slewing bearing.

Raceway contour accuracy: The contour shape of the raceway should meet the design requirements, and its error is usually controlled within ±0.05mm. The accuracy of the raceway contour directly affects the contact state between the steel ball and the raceway, and then affects the bearing capacity and movement performance of the slewing ring.

Positional accuracy

Concentricity: The coaxiality error of the inner ring and outer ring raceway is generally required to be no more than 0.05mm. Poor coaxiality will cause uneven stress on the two rows of steel balls, which may lead to overload damage to the steel balls and affect the normal operation of the slewing bearing.

Parallelism: For double row ball slewing rings, the parallelism error between the two rows of raceways is usually controlled between 0.05mm and 0.1mm. Excessive parallelism error may lead to uncoordinated movement of steel balls between two rows of raceways, increase friction and wear, and reduce the efficiency and life of slewing rings.

Surface roughness

The surface roughness of the raceway is generally required to be between Ra0.8μm and Ra1.6μm. The surface roughness directly affects the coefficient of friction and the contact fatigue strength between the ball and the raceway. If the surface roughness is too large, it will increase the frictional resistance, leading to increased heating and wear; The surface is too smooth, which may affect the adsorption of lubricating oil and is not conducive to the long-term operation of slewing rings.

Hardness

The hardness of the raceway surface is usually required to be between HRC58 - HRC64. The appropriate hardness can ensure that the raceway has good wear resistance and fatigue resistance, can withstand the load transmitted by the steel ball, and at the same time avoid defects such as cracks due to the increase in brittleness of the material due to excessive hardness.

The raceway accuracy requirements for double row ball slewing rings may vary depending on the application area and operating conditions. For example, in high-precision aerospace equipment or semiconductor manufacturing equipment, the accuracy requirements for slewing ring raceways will be higher, while in some ordinary construction machinery, the accuracy requirements are relatively low.

Supplier of double row ball slewing rings

LZTC Double Row Ball Slewing Rings provides a series of services such as R&D, design, production and sales of double row ball slewing ring products. If you are looking for a double row ball slewing ring supplier, please contact us for the latest quote.