Marine crane slewing bearing

With the development of offshore oil rigs, there is an increasing demand for large lifting equipment for platform installation and maintenance.

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1. The requirements of basic function parameters are continuously improved. The lifting capacity of a single machine is basically above 1000t, the maximum working range can reach nearly 100 meters, and the lifting height of 2000 meters can be achieved, and the crane can be fully rotated.

2. Higher requirements are also placed on the effective working area of the lifting ship deck. Users often require lifting equipment to occupy a smaller deck area as possible.

3. In addition, there are also users who request to reduce the radius of the tail slewing and set the driving mechanism inside the rotating column. In order to reduce the external dimensions of the crane, it is not allowed to reduce the tipping moment by adding a balance weight.

In short, the development of offshore engineering cranes requires more and more superior performance and more and more compact forms. These requirements put a severe test on the design and manufacture of crane slewing bearings. To meet these requirements, the slewing ring is usually of the rotary column type and is installed below the deck of the ship.

The current rotary slewing bearing is usually composed of a set of upper rollers and a bottom radial thrust bearing. The upper roller is subjected to the horizontal force generated by the tilting moment, and the bottom radial thrust bearing is subjected to both horizontal force and vertical force.

The maximum lifting torque of a large-tonnage slewing crane can reach more than 100,000 Nm. In this case, the horizontal and vertical forces of the slewing bearing are relatively large, and the load can reach more than 3000t.

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For the upper roller, there is great difficulty in the design of the single roller. The bearing capacity of the single roller is limited. In order to achieve the bearing capacity, the method of increasing the diameter and the number of the roller is adopted, which causes the roller to occupy too much deck space, which is unacceptable to the user; The friction coefficient is large, and the generated rotational resistance is correspondingly increased, resulting in an increase in the rotational drive power.

For the bottom radial thrust bearing, bearing horizontal force and vertical force bidirectional load, under the existing industrial conditions, it is not possible to design and manufacture a radial thrust bearing that can meet the above bearing capacity requirements. In the existing rotary slewing bearing form, the radial thrust bearing is also decomposed into a radial spherical bearing and a self-aligning thrust bearing, and the two bearings are respectively subjected to horizontal force and vertical force, so as to ensure automatic positioning, The center of the two bearing spheres coincides with one point. It is usually suitable for applications with small loads and sizes, and machining can guarantee accuracy.

After the size becomes larger, due to machining capacity limitation, manufacturing and installation errors, and structural deformation, it is impossible to achieve concentricity of the two bearings, which may easily cause the bearing to be partially stuck during operation, and cannot be rotated, resulting in early damage of the bearing, and the consequences are quite serious.

In view of the problems in the prior art mentioned above, it is necessary to study and design a new type of slewing bearing device for a marine ship-borne crane, thereby overcoming the problems existing in the prior art.

How to choose machine tool spindle and turntable bearing.

As the core component of the machine tool spindle and turntable, the bearing plays a decisive role in the performance of the machine tool. This paper mainly describes the selection of spindle bearings and the selection of rotary table bearings.

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As a key component of the machine tool, the spindle directly affects the parameters such as the rotation accuracy, rotation speed, rigidity, temperature rise and noise of the machine tool, which in turn affects the machining quality of the workpiece, such as the dimensional accuracy of the part and the surface roughness.

Therefore, in order to maintain excellent machine tool processing capabilities, high-performance bearings must be used. The accuracy of the bearings used on the machine tool spindle should be ISO P5 or higher (P5 or P4 is the ISO accuracy level, usually from low to high is P0, P6, P5, P4, P2), and for high-speed CNC machine tools, machining centers, etc. For high-precision machine tool spindle bearings, ISO P4 or higher accuracy is required; spindle bearings include angular contact ball bearings, tapered roller bearings, and cylindrical roller bearings.

Among the above types of bearings, precision angular contact ball bearings are the most widely used. We all know that the rolling element of an angular contact ball bearing is a ball; because it is a point contact (distinguished from the line contact of the roller bearing), it can provide higher speed, smaller heat generation and higher rotation. Precision. In some ultra-high-speed spindle applications, hybrid bearings with ceramic balls (typically Si3N4 or Al2O3) are also used. Compared with the traditional fully hardened steel ball, the ceramic ball material itself gives the ceramic ball bearing the characteristics of high rigidity, high rotation speed, high temperature resistance and long service life, so as to meet the demand of high-end customers for machine tool bearing products.

In terms of the contact angle of the angular contact ball bearing, the contact angles of 15° and 25° are currently popular; usually the contact angle of 15° has a relatively high rotational speed performance, and the contact angle of 25° has a high axial direction. Carrying capacity. Because the choice of preloading has a great influence on the application of precision angular contact ball bearings, for example, in high load bearing and high rigidity, medium or heavy bearing preloading is generally used; for some high speed and high precision applications. In the early selection of bearings, we need to pay attention to choose the appropriate preload, generally light preload is more common. Preloading is generally divided into three types: light, medium and heavy. In order to facilitate the use of customers, several major bearing manufacturers in the world generally provide pre-grinded bearing end faces and preloaded bearings, which is what we usually call universal matching precision. Angular contact ball bearing form. This type of bearing eliminates customer preload regulation and saves installation time.

Precision tapered roller bearing

In some machine applications with heavy loads and speed requirements – such as the forging of forgings, the wire machine of oil pipelines, heavy duty lathes and milling machines, the selection of precision tapered roller bearings is an ideal solution. . Because the roller of the tapered roller bearing is designed for line contact, it can provide high rigidity and load to the main shaft. In addition, the tapered roller bearing is a pure rolling bearing design, which can reduce the bearing operation. Torque and heat to ensure spindle speed and accuracy. Since the tapered roller bearing can adjust the axial preload (play) during installation, this allows the customer to better optimize the bearing clearance adjustment throughout the life of the bearing.

In addition, in some high-speed applications where the inner ring rim speed is greater than 30 m/s, some specially designed tapered roller bearings can also meet the requirements, such as TSMA bearings or Hydra-Rib hydraulic floating rib bearings. The rib of the TSMA bearing has a plurality of lubricating oil holes in the axial direction, which can be lubricated by circulating oil or oil mist. The centrifugal force can distribute the oil to the contact area between the roller and the rib, so that the bearing can be more fully lubricated and the bearing can be improved. Rotating speed. The Hydra-Rib hydraulic floating rib bearing is designed to optimize the preload of the spindle system. The bearing has a floating rib that is in contact with the large end of the roller, unlike the common bearing with a fixed inner ring rib; The floating rib is positioned by the “pressure” system, which ensures that the bearing will perform at its best under all conditions and has been successfully used in domestic customers.

The rotary table commonly used in CNC machine tools has an indexing table and a CNC rotary table. When machining certain parts of CNC machine tools, in addition to the linear feed motion of the three coordinate axes X, Y, and Z, sometimes there is a need for circular motion around the three axes of X, Y, and Z. For A, B, C axis

The CNC rotary table can be used to achieve a circular feed motion. In addition to the circular feed motion, the CNC rotary table (referred to as the CNC rotary table) can also complete the indexing movement. The function of the indexing table is to transfer the workpiece to the surface, and the automatic tool changing device can be used together to realize the multiple installations of several surfaces in one installation of the workpiece, thus greatly improving the working efficiency. The shape of the CNC turntable and the indexing table are not much different, but the structure has a series of features. Since the CNC rotary table can realize the feed motion, it has much in common with the feed drive mechanism of the CNC machine. The difference is that the drive mechanism realizes the linear feed motion, and the CNC rotary table realizes the circular feed motion.

The rotary table is widely used in various CNC milling machines, boring machines, various vertical cranes, and vertical milling machines. In addition to requiring the rotary table to withstand the weight of the workpiece well, it is also necessary to ensure its rotation accuracy under load. The turntable bearing, as the core component of the turntable, not only has a high load carrying capacity during the operation of the turntable, but also needs to have high rotation precision, high anti-overturning capability, and high rotational speed capability. In the design of the rotary table, the types of bearings used are roughly divided into several types:

Thrust ball bearing + cylindrical roller bearing

Thrust ball bearings can withstand certain axial forces, so the bearings are mainly used to bear the weight of the workpiece; cylindrical roller bearings are mainly used for radial positioning and external radial forces (such as cutting force, milling force, etc.) . This type of design is widely used and relatively inexpensive. Since the thrust ball is a point contact bearing, its axial bearing capacity is relatively limited, and it is mainly used in small or medium-sized machine tool rotary table. In addition, the lubrication of the thrust ball is also difficult.

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Hydrostatic bearing + precision cylindrical roller bearing

A hydrostatic bearing is a plain bearing that supplies pressure oil externally and establishes a static pressure bearing oil film in the bearing to achieve liquid lubrication. Hydrostatic bearing always works under liquid lubrication from start to stop, so there is no wear, long service life and low starting power. In addition, this bearing also has the advantages of high rotation precision, large oil film stiffness, and can suppress oil film oscillation. Precision cylindrical roller bearings have good radial bearing capacity, and thanks to the use of precision bearings, the rotary table’s rotation accuracy is also well guaranteed.

The rotary table designed with this type can withstand high axial forces. Some workpieces weigh more than 200 tons and the turntable has a diameter of more than 10 meters. However, this type of design also has some shortcomings. Because the hydrostatic bearing must be equipped with a special oil supply system to supply the pressure oil, the maintenance is complicated and the cost is relatively high.

Crossed roller bearing

The application of crossed roller bearings on the turntable is also relatively common. Crossed roller bearings are characterized by two raceways in the bearing and two rows of rollers arranged in a row. Compared with the traditional thrust bearing + radial centering bearing combination, the cross roller bearing is compact, compact and simplifies the table design, thus reducing the cost of the turntable.

Introduction about the process of slewing bearing processing

1. Inspection of forging blanks

First understand the material of the blank and the state after forging before processing. Secondly, it is necessary to check whether the blank has defects such as lamination and cracks.
Measure the dimensions of the blank. Including the inner and outer diameter of the blank, the height dimension, calculating the machining allowance, and estimating the number of times of turning in the turning process more accurately.

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2. Turning processing

Roughing: Roughing according to the turning process drawings, the cutting speed and cutting amount are strictly in accordance with the process regulations (the general cutting speed is 5 rev / min. The cutting amount is 10mm ~ 12mm).

Rough aging: After the roughing of the bearing parts is completed, the three-point support is adopted, and the flat parts are not allowed to be stacked. The aging time is not less than 48 hours before the finishing of the car can be carried out.

When the precision bearing parts are finished, the cutting speed is 6 to 8 revolutions per minute, and the cutting amount is 0.3 to 0.5 mm.

Forming Finishing Car: When the bearing parts are finally formed into the finished car, in order to prevent the parts from being deformed, the fixed clamping device of the parts must be loosened, so that the parts are in a state of no force, the turning speed is 8 revolutions per minute, and the cutting amount is 0.2 mm.

Cross, three-row roller slewing bearing inner ring special process: In order to prevent crossover, the inner ring of the three-row roller slewing bearing is deformed after heat treatment. In the turning process, it is necessary to carry out pair processing, that is, the raceway back-to-back processing, no cutting before heat treatment, and cutting after heat.

After finishing the heat: After the heat treatment of the inner and outer rings of the bearing, the finishing process is carried out.

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3. Heat treatment

Quenching surface quenching: The bearing raceway surface is medium frequency quenched, the hardness is not less than 55HRC, the hardened layer depth is not less than 4mm, the soft belt width is less than 50mm, and the “S” mark is marked at the corresponding position.

After the heat tempering treatment: After the intermediate frequency quenching of the inner and outer rings of the bearing, it must be baked at 200 °C for 48 hours. To ensure the disappearance of internal stress.

4. Rolling and milling

For the slewing bearing with internal and external teeth, the hobbing process should be carried out before the grinding process, strictly in accordance with the process requirements, and the accuracy level should reach 8 or above.

5. Drilling

Marking: After measuring the dimensions of the parts, the lines shall be scribed according to the specified dimensions of the drawings. The positioning process shall not differ by more than 3 inches.

Drilling: Check the size of the scribe line against the drawing to ensure the correct size and then carry out the drilling process. The mounting hole of the slewing bearing of the inner body should be combined and processed, and the error of the hole distance of the 180C degree between the soft belts should not exceed 5‰.

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6. Grinding processing

Rough grinding: It adopts medium corundum, soft three-grain degree is 36 degrees, and the atmospheric hole resin grinding wheel is used for grinding. The line speed is controlled at 1500 rpm to prevent the raceway burn. The maximum grinding depth must not exceed 1 mm.

Fine grinding: Grinding with a particle size of 46 degrees or 60 degrees resin grinding wheel, the grinding amount is less than the rough grinding process, and the finish should reach the level specified in the drawings.

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7. Other parts

Rolling element: self-processing or steel ball roller of fixed-point manufacturer, the accuracy grade should meet the requirements of the drawings, the rolling elements are less than 5% of each other, and the surface magnetic particle inspection and ultrasonic flaw detection should be carried out before the bearing assembly, and the flaw detection report is issued.

Retainer: The retainer manufactured by the fixed-point manufacturer shall be used to meet the requirements of the drawings, and strict inspection shall be carried out before assembly and use, and a test report shall be issued.

Sealing ring: Sealing strip produced by fixed-point manufacturers. Strict testing should be carried out before assembly and inspection records should be issued.

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8. Assembly

Preparation clearance: After the grinding process, the test assembly shall be carried out in order to measure the preliminary clearance. According to the calculation data and the test clearance, the final grinding process shall be carried out, and the final drawings shall be used to define the clearance.

Parts inspection: After the clearance is completed, the final part inspection shall be carried out and recorded accordingly.

Demagnetization, cleaning, packaging and issuing a certificate.

 

Cross cylindrical roller slewing bearing

Definition and operation principle of crossed cylindrical roller slewing bearing

Definition: Cross-roller type slewing bearing consists of two races. It is compact in structure, light in weight, high in manufacturing precision, small in assembly clearance, high in installation accuracy, and 1:1 cross-arrangement of rollers. The force, tipping moment and large radial force are widely used in lifting and transportation, construction machinery and military products.

Cross cylindrical roller principle: Cylindrical rollers are arranged at right angles to each other at intervals between the inner and outer rings of the bearing. They can withstand loads from all directions (such as axial, thrust or momentum loads). The internal structure of the crossed roller bearing is arranged at 90° perpendicular to each other by rollers, and spacers or spacers are arranged between the rollers to prevent the inclination of the rollers and the friction between the rollers, thereby effectively preventing the rotational torque. increase.

In addition, the contact phenomenon or the locking phenomenon of the roller does not occur, and since the inner and outer diameters are divided structures, the gap can be adjusted, and even if the preload is applied, a high-precision rotational motion can be obtained.

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Application field of cross cylindrical roller slewing bearing

Cross cylindrical roller bearings have a split inner ring, a split outer ring, and an integral inner and outer ring from the outer structure. From the internal structure, there are full roller type, metal window cage and so on. Therefore, it is widely used in various occasions: joint parts or rotating parts of industrial robots, rotary tables of machining centers, rotating parts of robots, precision rotary tables, medical instruments, measuring instruments, and IC manufacturing equipment.

Use cases and technical analysis of crossed cylindrical roller slewing bearings in the robot industry:

Industrial robots typically use an articulated mechanical structure. The drive motor is independently installed in each connector, and the power amplifier circuit of the drive unit is controlled by a computer to realize the operation of the robot. The structure of an industrial robot is a closed loop system. Through the motion controller, servo drive, robot body, sensor and other components, the key products of the functional robots that people need are completed: welding robot, handling robot, painting robot, transmission robot.

The development of modern industrial robots tends to be lighter, and the bearings must be installed in a limited space that must be small and lightweight, ie lightweight. At the same time, the robot has high load, high rotation precision, high running stability, fast positioning speed, high repeatability, long life and high reliability. The required robot bearings must have high load capacity, high precision and high. Rigidity, low friction torque, long life and high reliability. Lightweight and high performance is a contradiction.

Technology: Industrial robots with thin-walled bearings not only have to ensure sufficient capacity, but also require precise positioning and flexible operation. Therefore, bearing design analysis determines the main parameters, not just the dynamic rated load as the objective function, and the rated motion Load, stiffness and friction torque are used as objective functions for multi-objective optimization design. At the same time, the finite element analysis method of thin-walled bearings based on ferrule and frame deformation is adopted.

The reason why the slewing ring/bearing is not working properly and the solution.

With the advancement of technology, the application of slewing bearings in construction machinery is more and more extensive. If we find that the slewing bearing can’t move, how can we deal with it? The following methods can help you to eliminate this problem.

1. The newly purchased products are not flexible. Please check the production date of the slewing ring. If the time is long (such as more than half a year) and the weather is cold, there may be impurities such as salt spray in the raceway, which may cause malfunction (cold area, winter is more prominent). Remedy: If you can work after the afterburner and no other abnormalities can be used normally.

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2. The operation is not flexible during use. The sealing strip is damaged, causing foreign matter to enter the raceway if the working condition is poor, the dust is immersed in the raceway, etc.); check the meshing of the large and small gears, whether there is any foreign matter or broken teeth.

3. The operation after installation is not flexible. It may not work well with the mounting surface of the mainframe and the mounting surface of the slewing bearing. As a result, the axial clearance of the slewing bearing after installation cannot compensate the deformation of the slewing bearing. The slewing bearing is in the negative clearance state, and the rolling elements are in the raceway. Difficulties in operation (sometimes accompanied by abnormal noise); or poor meshing of large and small gears; or foreign objects in the large and small gears.

Remedy: Rework the main machine installation plane so that the installation plane meets the requirements; re-adjust the gear meshing backlash according to the requirements, especially pay attention to the gear runout position; check to ensure that the large and small gear meshing position has no foreign matter; exchange a slightly larger slewing bearing .

This is a common situation in which the slewing ring can not be turned. In fact, it is far more than just these. In fact, as long as we install it correctly and regulate the operation, many problems can be avoided.

Maintenance of slewing ring (bering) in high temperature operating environment.

1. Which carriers use slewing rings to operate in high temperature environments

The slewing bearing of the ladle turret has a relatively poor working condition and is subject to high axial load and overturning moment. These loads are transmitted and received by the ring gear, the raceway of the raceway and the gear, so the slewing bearing is on the selected material. It is necessary to consider the tensile strength, compressive strength and fatigue strength of the material to be high and have sufficient toughness and wear resistance. The single-row four-point contact slewing bearing can simultaneously bear radial force, axial force and overturning moment, and is widely used.

In view of the bearing capacity of the slewing bearing in high temperature environment, based on the thermal stress analysis of the slewing bearing, the contact angle, the rolling element radius r, the raceway radius R and the rolling element radius r ratio, the hardened layer depth and Five aspects of the raceway hardness are proposed to improve the bearing capacity of the slewing bearing. Orthogonal test analysis is carried out for these factors, and the optimal combination of parameters is found to reduce the contact stress on the slewing bearing raceway and improve the slewing bearing at high temperature. The bearing capacity provides a theoretical basis for the structural optimization of the high-temperature single-row four-point contact slewing bearing.

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2. Precautions for slewing bearing high temperature operation

The slewing bearing is a new type of mechanical parts that has gradually emerged in the world for nearly forty years. The slewing bearing is a mechanical force transmission basic component that needs relative rotation between the two parts and simultaneously receives axial force, radial force and overturning moment. Its basic function is to fix it on the upper and lower supports of the mechanical equipment by bolts. The force transmission and transmission realize the relative rotation between the two parts of the mechanical equipment. The domestic slewing bearing market was originally mainly in the construction machinery industry.

The largest single-row four-point contact ball slewing bearing accounted for more than 95% of the total market share, and the diameter of the raceway was between Φ500 and Φ1500mm. Most of them have a small processing difficulty, a broad market, and low equipment cost. With the continuous development of engineering machinery, wind power industry, heavy-duty vehicles, metallurgical machinery, petroleum industry, military industry, etc., slewing bearings have been more widely used, and are also required to have more and better performance, one of which is the requirement With high temperature resistance, bearing raceways, cages, seals and lubricants can withstand certain high temperatures and maintain their performance.

High temperature slewing bearings for specific applications, in addition to withstand the alternating pressure, also withstand alternating temperature changes, which will produce fatigue, creep and their interaction. In order to ensure the mechanical properties and life of the product, higher requirements are put forward from material selection, machining process, heat treatment process, to corresponding tooling equipment and testing instruments.

3. How to maintain the slewing ring running in high temperature environment

The slewing ring is rolled to the inside with a small amount of grease. The activation allows the user to refill the new grease according to different working conditions.

The slewing bearing raceway should be filled with grease regularly. Generally, the ball support is refueled once every 100 hours of operation, and the roller type support is refueled every 50 hours. The special working environment, such as tropical, humid, dusty, large temperature difference and continuous operation, should shorten the lubrication cycle. New grease must be added before and after the machine has been shut down for a long time. For each lubrication, the raceway must be filled with grease until it seeps out from the seal. When filling grease, slowly turn the slewing ring to make the grease fill evenly.

The tooth surface should always be cleaned of debris and coated with the corresponding grease. There should be a lot of comprehensive work factors, and users can also choose the best grease according to specific requirements.

After the slewing bearing has been running for the first time for 100 hours, the pre-tightening force of the bolts should be checked. After every 500 hours of operation, the pre-tightening force must be maintained. Pay attention to the operation of the slewing bearing during use. If noise, shock and power suddenly increase, stop the machine immediately, check the fault, and dismantle it if necessary.

4. Quality requirements for slewing bearings in high temperature environments (blanks and accessories)

There are many manufacturers of slewing bearings, and the quality and price are also uneven. However, the factors affecting the price are mainly the product quality. The product quality gap is also mainly reflected in the quality of raw materials. The price of raw materials and the price of non-tempered products differs by 1000. Multivariate/ton, because the hardness of the material that is not tempered is only 140-170HB and the hardness of the material after quenching and tempering is 207-262HB, which is the biggest gap.

Secondly, the hardness of the raceway also affects the quality of the product. The hardness of the raceway of the Xuzhou Wanda slewing bearing is ≤3mm, and the depth of the hardened layer of the raceway quenching affects the service life of the product.

Once again, the precision control of each process in product processing, our products in the process of processing more than two other processes to ensure that the product is flexible, does not cause jamming or shaking.

Quality is the foundation of an enterprise’s survival and the soul of its development. Therefore, Luoyang Hengguan slewing bearing will provide you with the most cost-effective products. Quality products will also make us go further and further on the road in this industry. Getting better and better.

Slewing bearing common faults and solutions

Slewing bearings are a common mechanical part in industrial equipment. They have many good properties and advantages that can increase productivity in industrial production. However, in the long-term use of the slewing bearing, various failures will inevitably occur. The methods for solving various failures are as follows:

1. The newly purchased slewing bearing product is not flexible. Please check the production date of the slewing bearing. If the time is long (such as more than half a year) and the weather is cold, there may be a large viscosity of the grease in the raceway, which may cause malfunction (cold area, winter is more prominent).

Remedy: If it can work after the afterburning and no other abnormalities can be used normally; if there is abnormal noise, check whether there is serious trauma during transportation, and feedback the information to our company’s sales service department.

2. It is not flexible after installation. It may be that the mounting surface of the main assembly does not cooperate well with the mounting surface of the slewing bearing, so that the axial clearance of the slewing bearing after installation cannot compensate for the deformation of the slewing bearing, and the slewing bearing is in a negative clearance state, and the rolling elements are difficult to operate in the raceway (sometimes accompanied by different Sound); or poorly meshed gears; or foreign objects in the large and small gears. Remedy: a. Rework the host installation plane so that the installation plane meets the requirements; or use the gasket filling method.

b. Resize the gear meshing backlash as required, paying particular attention to the maximum position of the gear runout.

c. Check that there is no foreign matter in the meshing position of the large and small gears.

d. Replace a slewing bearing with a slightly larger gap.

(3) Inflexible operation during use

a. Lack of grease, fill as required

b. The sealing strip is damaged, causing foreign matter to enter the raceway (if the working condition is poor, the dust in the raceway invades the dust, etc.).

c. Check the meshing of the large and small gears, with or without foreign objects or broken teeth. If the above measures are taken, the slewing bearing cannot be rotated, and there may be a failure in the raceway. Please inform our after-sales service department.

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2. The slewing bearing that has just been shipped from the factory will give a uniform sound of the rolling of the steel ball during idling, which is normal. The slewing bearing is accompanied by a different kind of abnormal sound when it is installed after installation, which is called abnormal noise.

(1) The slight abnormal sound of the new product when it is idling, it will naturally disappear after turning for dozens of laps. If it does not disappear, it may be caused by slight deformation of the slewing bearing during transportation. However, if the operation is flexible and normal, it can be installed and used with confidence, and it will disappear naturally after a period of use. If the sound is loud or after a period of use (usually 2-4 months) has not disappeared, you should contact me in time.

(2) After the assembly, abnormal operation occurs during the test run. It should be checked whether the installation surface is level and meet the requirements. If the unevenness of the installation surface does not meet the requirements, the negative gap of the raceway will be generated and the noise will be abnormal. The treatment method is the same as “the operation after installation”. “Flexible”; or poorly meshed gears, loose when tight, and excessively tight at the maximum position of the tooth jump to produce abnormal noise.

(3) Abnormal noise is generated during use. (First of all, it should be determined whether the sound is emitted by the slewing ring. Some steel structures or other components make a sound, which is often mistaken for the sound of the slewing ring. Therefore, the rotation of the slewing ring can be stopped. Other components are in normal operation to discriminate the source of the sound. There are several reasons: the grease is missing in the raceway, and the rolling body and the block collide to make a sound. This sound can be eliminated after oiling in time; the raceway is mixed with foreign matter such as sand and iron. Such as scraping, this situation is often accompanied by difficulty in turning (generally this situation is prone to occur in harsh environments). At the same time, it should also pay attention to whether the sealing strip is damaged; the mounting bolt is loose, resulting in elastic deformation of the slewing bearing, negative gap in the deformation position, etc., to eliminate the above situation, such as the slewing bearing still has abnormal noise, please contact me.

 

3. After the slewing bearing is loaded, the clearance is about 3-5 times of the factory inspection (three-point inspection method), and can be used continuously within this range.

(1) The mounting bolts are loose, causing them to shake during work. Please inspect all inner and outer ring mounting bolts and tighten as required.

(2) The steel structure supporting the slewing bearing is not rigid enough, and elastic deformation occurs during loading, resulting in overall swaying of the slewing bearing. Increase the strength of the supporting slewing bearing steel structure.

(3) Check whether the operation is overloaded and operate in strict accordance with the regulations.

(4) Long-term overloading and causing the raceway to collapse, and the clearance is too large. Please let me know if this happens.

 

4. When there is a broken tooth in the broken tooth slewing bearing, the site should be protected and the company’s after-sales service department should be notified immediately for analysis and processing. (1) Broken teeth are often directly related to installation, and there are mainly the following reasons:

a. When installing the large and small gears, the side gap is not adjusted properly, and the requirements are not met, resulting in poor gearing of the two gears during operation. The backlash should be adjusted as required.

b. The meshing gap adjustment is not performed with the pinion gear at the maximum position of the tooth jump as required, causing the pinion gear to become stuck when the meshing gear is engaged with the maximum position of the large gear tooth jump. The meshing adjustment should be made with the pinion in the position where the green paint is applied, and the test operation should be carried out after adjusting according to the requirements.

c. The axis of the large and small gears is not parallel. After installation, the large and small gears mesh poorly, causing broken teeth. It should be ensured that the two gear axes are parallel.

d. The slewing bearing mounting bolts are not tightly fixed, and the large and small gears are poorly engaged, causing broken teeth. The bolts should be tightened as required.

(2) aspects of use

a. Violation of the operating procedures, overload and tell the rotation, the host collides (sweep) obstacles and so on. It should be operated strictly in accordance with the operating procedures.

b. Foreign matter is caught when the slewing bearing is engaged with the pinion. The size of the gears should be clean and checked frequently. Common faults and troubleshooting methods for slewing bearings

Slewing bearing is an important device of industrial machinery. It is a mechanical “joint”. Without slewing mechanical equipment, there is no good activity. Therefore, daily troubleshooting is very important, which not only guarantees the service life of the slewing bearing, but also Improve the utilization of slewing bearings, reduce maintenance costs and reduce costs. The slewing bearing is a more professional mechanical device, and it is also a special load that can withstand large axial loads, radial loads and overturning moments, and combines various functions such as support, rotation, transmission and fixing. Large bearing with structure. In the course of use, it will inevitably cause damage to the bearing. Its maintenance and maintenance also needs to be very careful. What is the specific maintenance operation procedure? Below, I will summarize some points for you to pay attention to, and we will introduce the common faults and troubleshooting methods of the slewing bearing device.

 

1. Rolling surface metal peeling The slewing bearing rolling elements and the inner and outer ring raceways are subjected to periodic pulsating loads, thereby generating cyclically varying contact stresses. When the number of stress cycles reaches a certain value, fatigue peeling occurs on the rolling element or the inner and outer ring raceways. Measures: First remove the roller or steel ball in the slewing ring to separate the inner and outer rings; then clean the raceway with gasoline; then use a sander (grinding wheel) to carefully produce around the needle stripping area of ​​Microsoft Corporation of the United States. Grinding the hardened layer of the crack, grinding the bottom of the stripping layer; preheating the welding torch with the welding torch for the raceway, and welding with the medium carbon steel electrode (the electrode must be dried before use and used with baking) ), to make the solder layer slightly higher than the surface of the raceway 1-2mm.

2. The high-precision slewing bearing of the burned burn of the slewing bearing has a tempering color on the raceway and the rolling element. The causes of burns are generally insufficient lubrication, the quality of the lubricant does not meet the requirements or deterioration, and the bearing assembly is too tight. Measures: partial repair welding or insert repair, the local repair welding method is: firstly grind the residual crack base of the damaged part with a portable grinding wheel, clean it with gasoline (oil); use the welding torch to preheat in this part, when it reaches After a certain temperature, the medium carbon steel electrode is used to weld the shape of the tooth in the damaged part of the tooth, so that it is 1-2mm higher than the tooth surface of the party; the experienced machine repair fitter is selected according to the tooth shape test until the tooth The shape meets the requirements.

 

3. Plastic deformation of slewing bearing Non-uniform pits appear on the contact surface between the raceway and the roller with high precision slewing bearing, indicating that the bearing is plastically deformed. The slewing bearing is subjected to a large static load or impact load, and the local stress of the working surface exceeds the yield limit of the material, which generally occurs on a low-speed rotating bearing. Measures: If the deformation is serious or the area is large, the layered welding should be carried out in layers, and the temperature of the base metal should not be too high to cause deformation; this avoids the rapid cooling to produce welding cracks, and the heat preservation measures should be taken immediately after welding to gradually cool him. . After cooling, use a sander to smooth the repair layer so that it is slightly higher than the raceway surface. Gradually repair the repaired weld layer with a whetstone or metallographic abrasive cloth to make it conform to the height of the normal surface of the raceway, with the corresponding original curvature. The sample is tested until it is qualified; the grease is cleaned on the raceway and the roller (steel ball) and assembled into one.

4, the slewing bearing seat crack bearing seat ring cracks may be caused by high-precision slewing bearing too tight, high-precision slewing bearing foreign or inner ring loose, bearing containment parts deformation, mounting bearing surface processing and so on. Action: When a whole seat is damaged, it can be cut along the root of the tooth, and then the root of the tooth ring is shaped into a certain shape. Then, a tooth is registered and cut on the same kind of waste seat ring, and processed into a shape corresponding to the base material, and then placed in the groove, and the positioning is clamped by the seat-shaped template. In order to ensure the consistency of the seat distance, and use the double wire clamp to increase the value, and then weld around the seat with low carbon steel. Finally, the weld is flattened with a tool such as a file.

The difference of bearing capacity of different types of bearings.(slewing ring bearing)

Deep groove ball bearings are the most common type of rolling bearings. The basic deep groove ball bearing consists of an outer ring, an inner ring, a set of steel balls and a set of cages. The deep groove ball bearing types are single row and double row. The deep groove ball structure is also divided into two types: sealed and open. The open type refers to the bearing without sealing structure. The sealed deep groove ball is divided into dustproof seal and oil proof. seal. The dust seal cover material is stamped from steel plate, which is simple to prevent dust from entering the bearing raceway. The oil-proof type is a contact type oil seal, which can effectively prevent the grease inside the bearing from overflowing.

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Deep groove ball bearings are mainly subjected to radial loads and can also withstand radial loads and axial loads. When it is only subjected to radial loads, the contact angle is zero. When the deep groove ball bearing has a large radial clearance, it has the performance of an angular contact bearing and can withstand a large axial load. The deep groove ball bearing has a small friction coefficient and a high limit speed.

The deep groove ball bearing has a simple structure and is easy to achieve high manufacturing precision compared with other types, so it is easy to be mass-produced in series, and the manufacturing cost is also low, and the use is extremely common. In addition to the basic type, deep groove ball bearings also have various modified structures, such as: deep groove ball bearings with dust cover, deep groove ball bearings with rubber seals, deep groove ball bearings with snap grooves, and Deep groove ball bearings with large load capacity of ball notches, double row deep groove ball bearings.

Deep groove ball bearings generally use steel stamped cages or brass solid cages. When the outer diameter is less than 400 mm, the steel stamping cage is not added with a post code. When the outer diameter is larger than 400 mm, the brass solid cage is not used with a post code.

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1.Self-aligning ball bearing

The self-aligning ball bearing is a bearing equipped with a spherical ball between the inner ring of the two raceways and the outer ring of the spherical raceway.
The center of curvature of the outer raceway surface is identical to the center of the bearing, so it has the same self-aligning function as the self-aligning ball bearing. When the shaft and outer casing are deflected, they can be adjusted automatically without increasing the bearing load.

Spherical roller bearings can withstand radial loads and axial loads in both directions. The radial load capacity is large, and it is suitable for heavy load and impact load. The inner ring inner diameter is a tapered bore bearing that can be mounted directly. Or use the adapter sleeve and the removal cylinder to mount on the cylindrical shaft. The cage uses a steel stamping cage, a polyamide forming cage and a copper alloy cage.

The self-aligning ball bearing has two structures of a cylindrical hole and a tapered hole, and the material of the cage is steel plate, synthetic resin and the like. The characteristic is that the outer ring raceway has a spherical shape and has self-aligning property, which can compensate the error of the heart ball bearing by different degrees of heart and shaft deflection, but the relative inclination of the inner and outer rings must not exceed 3 degrees.

Can withstand large radial loads while also withstanding a certain axial load. The outer ring raceway of this type of bearing is spherical, so it has the function of self-aligning. When the shaft is bent or tilted so that the center line of the inner ring and the center line of the outer ring are inclined no more than 1°~2.5°, the bearing can still work.

The inner diameter of the self-aligning ball bearing is cylindrical or conical. The conical inner bore has a taper of 1:1 2 or 1:30. In order to enhance the lubrication performance of the bearing, an annular oil groove and three oil holes are machined on the outer ring of the bearing.

It is mainly subjected to radial loads and can withstand small axial loads. The axial displacement of the shaft (housing) is limited to the clearance limit, and has automatic self-aligning performance, allowing normal operation under the condition that the inner and outer sides are relatively inclined, and is suitable for the parts in which the support seat hole cannot strictly guarantee the coaxiality.

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The self-aligning ball bearing with dust cover and sealing ring has been filled with the proper amount of grease. It should not be heated or cleaned before installation. It does not need to be relubricated during use. It can adapt to operating temperature – 30 °C to + 120 °C. between. Main purpose of self-aligning ball bearings: Suitable for precision instruments, low noise motors, automobiles, motorcycles and general machinery, etc. It is the most widely used type of bearing in the machinery industry.

2. Cylindrical roller bearing

Cylindrical rollers and raceways are line contact bearings. Load capacity, mainly bear radial load. The rolling element has little friction with the ferrule rib and is suitable for high speed rotation. According to the ferrule with or without ribs, it can be divided into single row cylindrical roller bearings such as NU, NJ, NUP, N, NF, and double row cylindrical roller bearings such as NNU and NN. The bearing is a structure in which the inner ring and the outer ring are separable.

Cylindrical roller bearings with no ribs on the inner or outer ring, the inner and outer rings can move relative to the axial direction, so they can be used as free end bearings. A cylindrical roller bearing with a single rib on one side of the inner and outer rings and a single rib on the other side can withstand a certain degree of axial load in one direction. Steel stamping cages or copper alloy solid cages are generally used. However, some use polyamide shaped cages.

The cylindrical roller is in line contact with the raceway and has a large radial load capacity. Suitable for both heavy and shock loads, as well as for high speed rotation.

Cylindrical roller bearing raceways and rolling elements are geometric. After the improved design, the new load-bearing capacity, the new structural design of the rib and the roller end face not only improve the axial bearing capacity of the bearing, but also improve the lubrication conditions of the contact area between the roller end face and the rib, and improve the lubrication condition. Bearing performance.

The cylindrical roller is in line contact with the raceway and has a large radial load capacity. Suitable for both heavy and shock loads, as well as for high speed rotation.

Cylindrical roller bearing raceways and rolling elements are geometric. After the improved design, the new load-bearing capacity, the new structural design of the rib and the roller end face not only improve the axial bearing capacity of the bearing, but also improve the lubrication conditions of the contact area between the roller end face and the rib, and improve the lubrication condition. Bearing performance.

3.Single row angular contact ball bearings

Single row angular contact ball bearings can only withstand axial loads in one direction and will cause additional axial forces when subjected to radial loads. And can only limit the axial displacement of the shaft or housing in one direction. Angular contact ball bearings have a contact angle of 40 degrees and can withstand large axial loads. Angular contact ball bearings are non-separable designs with different shoulder heights on the sides of the inner and outer rings. In order to increase the bearing capacity of the bearing, the shoulder on one side is machined lower, so that the bearing can be loaded with more steel balls.

Double row angular contact ball bearings can withstand large radial loads and mainly combine radial and axial load and moment loads, limiting axial displacement of both sides of the shaft. Mainly used to limit the axial displacement of the shaft and the shell. The tiltability between the inner and outer rings of the double row angular contact ball bearing is limited. The allowable tilt angle depends on the internal clearance of the bearing, the bearing size, the internal design and the action.

The force and moment on the bearing, and the maximum allowable tilt angle should ensure that there is no excessive additional stress in the bearing. If there is a tilt angle between the inner and outer rings of the bearing, it will affect the life of the bearing, and at the same time, the bearing running accuracy will decrease and the running noise will increase. Double row angular contact ball bearings typically use a nylon cage or a brass solid cage.

Bearings going to Russia are subject to anti-dumping duties that can be settled through re-exports

The Ministry of Industry and Trade of the Russian Federation initiated an anti-dumping investigation on rolling bearing products originating in China. On December 13, 2007, the Russian federal government decided to adopt anti-dumping measures against rolling bearing products originating in China, and implemented a 31.3%-41.5% anti-dumping tax rate, valid for 5 years. On September 18, 2012, the Eurasian Economic Commission launched the first anti-dumping sunset review investigation on the products involved in China.

On September 17, 2013, the Eurasian Economic Commission made an anti-dumping sunset review of the products involved in China, and extended the anti-dumping measures for five years. On September 18, 2017, the Eurasian Economic Commission launched a second anti-dumping sunset review investigation on China’s rolling bearing products. The investigation period of dumping and damage in this case was from July 1, 2016 to June 30, 2017.

Bearing anti-dumping

Such a high anti-dumping duty will bring a heavy blow to China’s bearing export to the Russian market! China’s bearing export enterprises are forced to give up the Russian market! However, we know that Russia’s bearing requirements for China are relatively large. It is a pity that such a large market will give up because of anti-dumping duties!

In order to enable our country’s bearings to export Russian enterprises to continue to maintain the Russian market after anti-dumping, our company has opened up a channel for bearing the third country’s entrepot trade, and entered the Russian market through the third country curve, thus achieving the purpose of avoiding Russian anti-dumping duties.

We know that Russia does not have anti-dumping duties on bearings in all countries, so our solution comes: We first transport the goods to a third country (such as Malaysia, Thailand, etc.). After the goods arrive in a third country, we arrange customs clearance. Change the cabinet, issue a full set of documents from a third country (such as certificate of origin, packing list, INV, bill of lading, etc.), and then re-export to Russia. After the goods arrive in Russia, the customs clearance is a full set of documents from the third country. Such high anti-dumping Tax can be effectively avoided. This is what we call entrepot trade. We have started to operate after obtaining the consent of domestic and foreign customers, especially some foreign BUYER, I really like…

Bearing anti-dumping

The process of re-export operation is as follows:

1) Our company starts to carry goods from any port in China (Tianjin, Qingdao, Shanghai, Ningbo, Shenzhen, Guangzhou Port, etc.), and sends the goods safely to the transit port of the third country. The consignee is designated by our company. Our company is responsible for Re-export port import customs clearance.

2) When the goods are ready to leave the mainland, our company will arrange a two-way schedule according to the needs of the guests, and do BOOKING. After the arrival of the first-way (China-transit port), the container will be put in time and replaced at the terminal. Photographs of changing cabinets will be taken when changing cabinets to ensure the integrity and safety of the goods.

3) After completing the change of the cabinet, take the second-pass (transfer port-destination port) ship, get the bill of lading within 3-5 working days, and make the certificate of origin with the bill of lading. Prior to this, our company will be more correct with the Chinese shipper to do the documents.

4) After all the documents (Bill of Lading, FORM A/CO, INV, Bill of Lading, K2, etc.) are published, we will send the full set of original documents to your company or directly to the destination port. The destination port is used for customs clearance. A full set of documents from the three countries.

I hope that we can win more international markets for more enterprises in China that have encountered trade barriers through this third country re-export!

Personalized development of slewing bearings

With the continuous development of construction machinery, according to the individual needs of users, the construction machinery is oriented towards the individual direction. For example, the excavator has large and medium-sized excavators, and various excavators for improving special purposes. Therefore, the requirements for the personalized development of slewing bearings are put forward. Today, the author mainly talks about the individualized development of slewing bearings.

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1. Individualized development of different sizes. Due to the inconsistency of various engineering machinery sizes and models, it is also necessary to adapt the size of the slewing bearing.

2. Special-purpose slewing bearings, such as the maximum bearing capacity, with the development of engineering machinery, toward the direction of large-scale development, some engineering machinery has hundreds of tons, so the maximum bearing capacity requirements of slewing bearings continue to increase.

3. Different temperature requirements, the mechanical application environment is now expanding, the total high temperature, high humidity, high salt environment and cold environment, the exhibition center is required to adapt.

4. Low failure rate requirements. With the development of aerospace technology, slewing bearings are required to have ultra-low failure rate characteristics.

In summary, with the development of engineering machinery, new requirements for slewing bearings have been put forward. The development of individualized engineering machinery requires the development of slewing bearings to meet the needs of construction machinery, and also the slewing bearing individualization. The driving force for development and the inevitable development.