2022 September the Third Week VISTA Technical Knowledge: Design improvement of shrinkage die for super large tapered roller bearing cage

Hot tags: tapered roller bearing(6)


Abstract: through the failure analysis of super large tapered roller bearing cage and the analysis of the shortcomings of the original shrink die, the characteristics and application effects of the improved shrink die are introduced in this paper.

Key words: bearing; cage shrink; die


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1. Introduction

Extra large tapered roller bearing is widely used in metallurgical industry because of its heavy load and high speed characteristics. Tapered roller bearings are generally divided into single row, double row and four row according to their structural characteristics. When the bearing is running, the working clearance of the bearing is one of the important parameters of the rolling bearing, which has a great impact on the service life, temperature rise, vibration and noise of the rolling bearing. Therefore, it is very important to reasonably select the working clearance of rolling bearing and control it within an optimal range. In practical application, the working clearance of rolling bearing is generally smaller than its original clearance due to the limitation of installation coordination and equipment conditions. When the rolling bearing is installed on the shaft or in the bearing seat by interference fit, the inner race of the inner race of the bearing expands and the outer race of the outer race compresses, resulting in the reduction of the internal clearance of the bearing. It is very important to meet the service requirements of bearings and improve the service life of bearings.

 

2. Role of cage in bearing

When the rolling mill bearing is in operation, it is impacted by the rolling elements, and the cage will produce high-frequency nonlinear vibration under the coupling action of bending moment and torque. Therefore, the quality of its sleeve and rotation performance directly affect the production cost, operating characteristics, working accuracy and service life of the rolling mill. In order to meet the rolling requirements of high speed, heavy load and long service life, it is required that the clearance and rotation flexibility and accuracy of bearing stamped cage are high.

 

The early failure of the bearing reduces the service life and reliability of the bearing, which seriously affects the working efficiency of the main engine and increases the production cost. Therefore, in the bearing production process, it is necessary to reduce the local deformation of the cage when it is assembled, so as to avoid early failure caused by local wear of the bearing in the use process. The failure modes of cage can be roughly divided into deformation failure, fracture failure, fatigue failure and corrosion failure according to its damage mechanism.

 

The cage of extra large tapered roller bearing is processed by integral stamping process. To meet the needs of sleeve closing, the cage is processed by stretching process before sleeve closing. When fitting radially, the cage must be shrunk to the original forming process size to ensure the radial clearance of the cage, ensure that the cage correctly guides the rollers to roll normally in the raceway, and the rolling elements can share the load. After tracking and analyzing the failed bearing, it was found that the failure was caused by local early wear of the cage.

 

3. Failure analysis of cage

3.1 the cage of the original shrinkage mold has the defect of inaccurate positioning during the process of assembling, resulting in the inconsistency between the cage rotation and the bearing rotation center after press fitting. After the sleeve is assembled, a point lock roller is often formed at the bottom of the cage to ensure the radial clearance of the bearing. But the roller cannot normally roll in the raceway. In the process of rotation, the rotation center of the cage should be close to the rotation center of the bearing. Because the cage is close to the point to lock the roller, the slope pressing surface of the cage is close to the inner ring raceway. The nearest lock point is subject to the greatest force, and the wear will be serious. Gradually, the radial clearance of the bearing will increase, causing mutual friction between the cage and the outer sleeve of the bearing, resulting in the wear failure of the cage.

 

3.2 the defects of cage point lock roller mainly show in three aspects:

(1) The early wear of the rib beam of the cage point lock is very serious.

(2) The support force of cage rib beam to rolling element is not uniform and linear, which seriously affects the bearing accuracy and rotation performance.

(3) The friction force of the bearing is increased and the temperature of the bearing is increased.

 

3.3 For bearings that lock the roller with a point, the contact surface between the cage and the rolling element is small, and the roller is prone to instability and abnormal noise.

 

4. Analysis of the original receiving and editing module

(1) Because oversize tapered roller bearings are not produced in large quantities, manufacturers usually use simple cage shrinkage molds when assembling tapered roller bearings, as shown in the figure.


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(2) Extra large taper roller bearing is difficult to move because of its overweight. It is not easy to take the whole set out of the mold after shrinking the cage when closing it. When the original shrinkage die was designed, there was a chamfer at the bottom.

 

(3) In the process of cage contraction, the cage and roller move down under force. When the required clearance is received, it is easy to collapse into the shape shown in the figure. The size of the original shrink die small head is the size of the cage small head, which is much larger than the process size of the cage small head. It is easy to bend the cage hole beam to the center diameter of the bearing, form a point lock type on the roller, and it is difficult to demould smoothly.

 

(4) During each contraction, the bottom surface of the cage is suspended and is not constrained by any supporting surface. When the hole beam section of the cage is pressed by an external force, its surface will be warped and deformed.

 

(5) In order to make the clearance meet the requirements of the process design, the shrinkage force on the cage rib beam point is the largest, and the section is very easy to be scratched by the mold.

 

5. Design of shrinkage die after process improvement

Fig. 3 shows the improved design of the shrinkage die, which has the following characteristics:

(1) The size of a is 2mm-3mm smaller than the size of the outer diameter of the small head of the cage after actual forming.

 

(2) During the contraction process, the hole beam can be contracted from the bottom of the small head of the cage, and there will be no shrinkage scratch on the hole beam. The hole beam will not form a convex point in the radial direction of the shaft, which can make the pressing surface fully contact with the roller, and make the radial clearance of the bearing meet the requirements of the process design. The cage will wear evenly during the use of the bearing and will not fail early, which will make the bearing ineffective.


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(3) The hole beam will not be deformed, so that the rotation center of the cage coincides with the rotation center of the bearing, which meets the requirements of the process design. Through actual testing, the rotation of the bearing groove meets the requirements of the process design.

 

(4) The pressing surface of the cage can linearly restrict the rollers to roll well along the raceway, can uniformly carry the load, and reduce the bearing noise.

 

(5) The bottom is constrained by the base plate. During the contraction process, the bottom will not warp and the bottom will be flat.

 

(6)After the shrinkage is completed, start the hydraulic pressure to push the bearing out of the shrinkage die with the hydraulic driving force. The bottom of the bearing is flush with the upper end face of the shrink die, and the bearing can be easily taken out of the shrink die. Reduce labor intensity, improve production efficiency, ensure product quality, and track the comparison of sleeve taking and bearing sleeve fitting of the same specification. See Table 1.

 

Table 1


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6. Conclusion

After trial use in different specifications of bearing sleeves, the mold demoulds smoothly. The appearance of the cage shall be free of scratches, and the clearance shall be reduced to the size required by the process at one time. The cage rib beam is free of concave deformation and the bottom is free of warping deformation, which shortens the production cycle. The appearance of the contracted bearing assembly meets the requirements of the process design. This mold is reasonably designed and demoulded smoothly. Some parts can be designed into general-purpose parts, which can reduce production costs and have a leading level in the same industry.

 

More about VISTA Tapered Roller Bearing

Vista tapered roller bearing High-quality brand have excellent reputation and popularity, good after-sales service system, fast, and guaranteed product quality!

 

As a leading global tapered roller bearing manufacturer and supplier in China, we're featured by perfect solution for many kinds of bearing supplying, competitive price and fast delivery for each customer. Please rest assured to buy tapered roller bearing at the best price from Vista. For any special requirement, contact us now.

 

Tapered roller bearings are particularly designed to carry combined (radial and axial) loads. They have single, double and four-row tapered roller designs. The single row tapered roller bearings are able to accommodate radial loads and axial loads in one direction only. Under radial loads, axial component force is affected in the bearing which must be counteracted, so the bearings are normally adjusted against a second bearing.

 

As a tapered roller bearing manufacturer, Vista supplies the following tapered roller bearings for customers: metric and inch series single row tapered roller bearing, metric and inch series double row tapered roller bearing, four row tapered roller bearing.

 

Tapered Roller Bearing 

 

 


2022-09-13

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