What are the repair processes for slewing bearings?

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The slewing bearing is also called the slewing ring. It is a new type of mechanical parts. It is composed of inner and outer rings, rolling elements, etc. The slewing ring is a large-scale bearing that can withstand comprehensive loads, and can withstand larger axial and diameter at the same time. Bearing for load and overturning moment.

Generally, it is widely used in industry, and the effect of use is very good. The application of slewing bearings is special, and it must be operated under continuous shock, vibration, and overload. Therefore, the control of production technical parameters in the product manufacturing process is also It is more rigorous, with high bonding strength, no shedding, no hard spots, high surface finish, and adjustable hardness. However, damage is still inevitable, which requires special repair techniques to ensure the flexibility of the later application of the slewing ring.

Repair process of slewing bearing

Slewing Bearings

1. Low temperature iron plating method

Low-temperature iron plating is a commonly used method for repairing shaft parts in the industry, and it has a long history of application in other mechanical maintenance industries. Low-temperature iron plating is an electroplating technology with a fast iron plating speed. The one-time iron plating has a large thickness, a relatively mature process and high production efficiency. It is suitable for repairing the surface of agricultural machinery transmission shafts or parts.

2. Thermal spraying method

Thermal spraying method mainly uses high-speed airflow to spray molten metal material on the surface of partially worn parts, and then the size can be restored after processing. Thermal spraying technology includes many methods such as flame spraying, electric spraying and plasma spraying. The additional materials for spraying are often better than the raw materials, so after the slewing bearing is repaired, the parts in terms of wear resistance and corrosion resistance have been greatly improved.

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3. Surfacing method

The surfacing method is to use the welding process to surfacing a layer of welding material on the worn parts of the part, and then restore the original matching size of the part through mechanical processing. The surfacing process can achieve different material repair effects through the selection of welding rods or wires. The process has the advantages of high material strength after repair and faster repair speed, and is suitable for repairing parts with greater wear.

The performance of the correctly repaired bearing is equivalent to that of the new bearing, and all parameters such as clearance can meet the requirements of use. It is important to understand and identify the degree of damage to choose the correct repair plan. Bearing repair requires long-term technical accumulation and comprehensive basic data storage. Professionally trained personnel can judge whether the bearing needs to be repaired. Timely routine inspections, preventive maintenance and vibration analysis can grasp the appropriate repair time in time, so as to help companies economically repair damaged bearings.

Inventory of common slewing bearing damage failure causes analysis and solutions

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It is common for bearings to fail during operation, so there is no need to make a fuss. In the event of a failure, the key to determining the cause of the damage and handling it Today, the editor has counted some common slewing bearing damage failure causes analysis and solutions.

 Crack defects

Trouble phenomenon: partly notched and cracked.

1. The cause of the failure

①Excessive impact load; ②Excessive interference; ③Large peeling; ④Friction cracks; ⑤Poor accuracy of the installation side (too large corner round); ⑥Poor use (a copper hammer is used to insert large foreign objects).

2. Solutions

①Check the conditions of use; ②Set appropriate interference and check materials; ③Improve installation and use methods; ④Prevent friction cracks (check lubricant); ⑤Check the design around the bearing.

Rotation of slewing bearing is not flexible

Trouble phenomenon: bearing heating, jitter, stuck.

1. The cause of the failure

①The clearance is too small (including the clearance of the deformed part); ②Insufficient lubrication or improper lubricant; ③Excessive load (excessive preload); ④The roller is skewed.

Slewing Bearings

2. Solutions

①Set proper clearance (increase the clearance); ②Check the type of lubricant to ensure the amount of injection; ③Check the conditions of use; ④Prevent positioning errors; ⑤Check the design around the bearing (including heating of the bearing).

The hardness layer falls off

Trouble phenomenon: the running surface is peeled off, and it is obviously convex and concave after peeling off.

1. Reason

①Improper use due to excessive load; ②Poor installation; ③Poor precision of shaft or bearing box; ④Too small clearance; ⑤Intrusion of foreign matter; ⑥rusting; ⑦Hardness reduction caused by abnormal high temperature

2. Solutions

①Re-study the operating conditions; ②Re-select the bearing; ③Reconsider the clearance; ④Check the machining accuracy of the shaft and the bearing housing; ⑤Research the design around the bearing; ⑥Check the installation method; ⑦Check the lubricant and lubrication method.

Slewing Bearings

Scratches and jams

Trouble phenomenon: rough surface, accompanied by micro-dissolving; scratches between ring ribs and roller end faces are called jams

1. Reason

① Poor lubrication; ② Foreign matter intrusion; ③ Roller deflection caused by bearing tilt; ④ Oil breaking on rib surface caused by large axial load; ④ Surface roughness; ⑤ Large rolling element sliding.

2. Solutions

①Re-study lubricants and lubrication methods; ②Check the conditions of use; ③Set appropriate preload; ④Strengthen the sealing performance; ⑤Use the bearing normally.

The cage is damaged

Trouble phenomenon: loose or broken rivet, broken cage.

1. Reason

①Excessive torque load; ②High-speed rotation or frequent speed changes; ③Poor lubrication; ④Entrapped foreign objects; ⑤Large vibration; ⑥Poor installation (installation in tilted state); ⑦Abnormal temperature rise (resin cage).

2. Solutions

①Check the operating conditions; ②Check the lubrication conditions; ③Re-study the selection of the cage; ④Pay attention to the use of bearings; ⑤Study the rigidity of the shaft and the bearing box.

Rusty corrosion on the surface of the slewing bearing

Trouble phenomenon: Part or all of the surface is rusty, and it is rusty in the form of pitch of rolling elements.

1. Reason

①Poor storage condition; ②Improper packaging; ③Insufficient rust inhibitor; ④Intrusion of moisture, acid solution, etc.; ⑤Hold the bearing directly by hand.

2. Solutions

①Prevent rust during storage; ②Strengthen the sealing performance; ③Check the lubricating oil regularly; ④Pay attention to the use of bearings.

Abrasion

Trouble phenomenon: red rust-colored wear particles are produced on the mating surface.

1. Reason

①Insufficient interference; ②Small bearing swing angle; ③Insufficient lubrication (or in a non-lubricated state); ④Unstable load; ⑤Vibration during transportation.

2. Solutions

①Check the interference and lubricant coating status; ②The inner and outer rings are packaged separately during transportation, and pre-pressure is applied if they cannot be separated; ③Reselect the lubricant; ④Reselect the bearing.

Slewing Bearings

Wear

Phenomenon: Surface wear, resulting in dimensional changes, often accompanied by abrasion and wear marks

1. Reason

①The lubricant is mixed with foreign matter; ②The lubrication is poor; ③The roller is skewed.

2. Solutions

①Check lubricant and lubrication method; ②Strengthen sealing performance; ③Prevent positioning error.

Indentation bruises

Trouble phenomenon: surface pits caused by stuck solid foreign objects or impact and scratches caused by installation

1. Reason

①Intrusion of solid foreign matter; ②Insert the peeling sheet; ③Shock and fall off caused by poor installation; ④Install in an inclined state.

2. Solutions

①Improve the installation and use methods; ②Prevent foreign matter from entering; ③If it is caused by metal sheets, check other parts.

Electric erosion

Resolve the phenomenon: the rolling surface has a pit-like pit, and the further development is in a wave plate shape.

1. Reason

The rolling surface is energized.

2. Solutions

Make a current bypass valve; take insulation measures to prevent current from passing through the inside of the bearing.

The above is the explanation of the common slewing bearing damage failure phenomenon, the reason analysis and the solution measures. I hope everyone will be helpful after reading it. Analyzing the damage and failure forms of the slewing bearing can provide a detailed reference for the design and selection of the bearing, and then improve the design, rationally select the bearing, give full play to the function of the bearing, increase economic benefits, and increase the service life.

What is the slewing ring gear module?

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Slewing bearing is one of the important parts of many modern machinery and equipment. It is called “joint of machine”. Many people are familiar with various parameters of slewing bearing, including clearance, inner and outer diameter, friction coefficient, etc. Many friends don’t know the module of supporting gear. The technical staff of Longda Bearing, a slewing bearing manufacturer, will give us a detailed introduction to this problem.

1. What is the module of slewing ring gear

The length of the arc (gear)/straight line (rack) occupied by a single gear tooth in the indexing circle (gear)/or line (rack), its length is π * m, and m is the modulus.

What does the module of the slewing ring represent: The module of the slewing ring represents the product of the tooth pitch and the number of teeth of the slewing ring gear, which is the circumference of the index circle. The gear modulus of the slewing ring determines the size of the tooth. The gear modulus is a basic parameter for the calculation of the gear size. The symbol is “m”. Gear cutters can be standardized, so that the standard modulus of gears can be standardized for mass production. Facilitate the replacement of later accessories. In the same way, “modulus” refers to the ratio of the pitch t between the tooth profiles of two adjacent gear teeth on the same side and the circumference ratio π (m=t/π), in millimeters.

If the number of teeth of the slewing ring gear is constant, the larger the gear modulus, the larger the radial dimension of the gear. The teeth of a gear with a large modulus are thick, and for two gears with the same number of teeth, the outer circle of the gear with a large modulus is larger. Therefore, the modulus of the gear in a watch is very small, and the modulus of the flywheel and transmission gear on the mechanical punching machine is large. The modulus of the two meshing gears must be the same. Modulus is the basic parameter of gear design, and it is used in many calculations of gear design.

Slewing Bearings

2. Reasonable selection of gear module

When designing a gear, one of the important parameters is this modulus. The gnawing of the gear will produce gnawing pulsation. The main reason is that it has a great relationship with the elastic deformation of the gear teeth. It is a basic part of the gear design. Parameter-gear modulus, if it is a relatively large modulus (that is, a gear with a relatively large size), it will also have a relatively large load-bearing capacity. The modulus parameter is inversely proportional to the degree of bending of the gear teeth. The increase of the modulus means that the rigidity of the gear teeth is improved, so that the elastic deformation of the gear teeth will not be great when the gnawing transmission is carried out, which greatly reduces the impact force formed by the gear teeth, thereby achieving The purpose is always greatly reduced. Therefore, from this point of view, the modulus should be increased appropriately, but the error generated when machining gears is also related to the modulus. If the modulus is increased, the tooth profile and pitch will also be increased. At this time, the error of gnawing noise will also increase accordingly, so the choice of modulus should be determined according to the specific situation.

Slewing Bearings

In the case of keeping the modulus unchanged, the diameter of the gear is proportional to the number of teeth, so the change of the number of teeth will also change the bending amount and elastic rigidity of the gear teeth: the strength of the noise generated by the sound source is not only related to the energy of the vibration source It is related to the size of the radiation area. If the radiation area is increased, the radiation power will also increase. Increasing the gear diameter will increase the noise radiation area, which will greatly affect the gear. Effective control of noise.

Therefore, in the relevant design, within the permissible range of ensuring the strength of the gear, the number of small teeth and the small modulus should be used as much as possible, and the reasonable selection of materials and heat treatment methods can be combined to promote the increase of the strength of the gear teeth, thereby reducing the diameter of the gear teeth. Then, the purpose of reducing gear noise is achieved.

What is the gear making process of slewing bearings

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Gear processing is a time-consuming process in the production of slewing bearings, and it is also one of the main factors that have restricted the production efficiency of slewing bearings. Based on the actual machining data, the application of milling and hobbing processes in the processing of turntable bearing teeth is compared from the aspects of efficiency and cost, which provides a basis for the reasonable selection of turntable bearing teeth processing technology and equipment. Today, the editor will come to talk with you about the tooth-making process of slewing bearings.

1. Material selection of slewing bearing blank

Generally, 50Mn is used for the slewing bearing ring. After surface quenching, the raceway hardness is HRC55-62. However, sometimes 42CrMo is selected to meet the needs of the host for special applications, which has a higher hardness. LDB’s selection of blank suppliers has undergone strict screening and strictly follows the traceability procedure. For each blank, from receipt to finished product, it can trace the source of the blank according to its serial number, quality inspection and other whole-process data.

Slewing Bearings

2. The technology of making gears from slewing bearings

1. The equipment used in the gear processing department still uses a large number of ordinary gear hobbing machines and gear shaping machines. Although it is convenient to adjust and maintain, the production efficiency is low. If a large capacity is completed, multiple machines are required to produce at the same time. In order to solve the problem of low processing efficiency, while increasing the number of gear hobbing machines and gear shapers, high-speed gear milling machines are used, which has high processing efficiency and good surface finish quality.

2. Some slewing bearings used under severe conditions require surface quenching treatment, such as excavators, pile drivers, wood grabs, graders and other operating conditions, which have relatively large impact loads and require quenching treatment on the tooth surface. The hardness after quenching of several sizes is between 45-60HRC. For common working conditions such as cranes and tower cranes, the tooth surface does not need to be heat treated.

3. With the rapid development of Industry 4.0, slewing bearings are more and more widely used in the automation industry. In this application field, the accuracy requirements for the teeth are relatively high, and the low requirements are also 8 levels of accuracy. In response to the rapid changes in the market, during the construction of the new plant, higher accuracy requirements are required for the equipment to meet the market demand.

4. After the tooth-making process is completed, there are follow-up processes such as fine turning, plane, drilling, track grinding, and assembly, and the slewing bearing can be shipped out of the factory.

3. Introduction to the failure analysis of the slewing bearing gear

1. Improper adjustment of the backlash of the large and small gears during installation, which did not meet the requirements, resulting in poor meshing of the two gears during operation, resulting in broken teeth. The backlash should be adjusted strictly as required.

2. Failure to adjust the meshing gap with the pinion at the maximum position of the gear jump as required, causing the pinion to jam when meshing with the maximum gear jump position during operation, causing tooth breakage. The meshing adjustment should be carried out at the position painted with green paint and the pinion gear should be adjusted according to the requirements for trial operation.

3. The axes of the large and small gears are not parallel, and the large and small gears mesh poorly after installation, causing tooth breakage. It should be ensured that the axes of the two gears are parallel.

4. The mounting bolts are not fastened tightly, and the gears of large and small meshes are not well meshed, causing gear breakage. The bolts should be tightened as required.