slewing bearing being difficult to rotate cause

slewing bearing being difficult to rotate cause

The following items are the possibility of the slewing ring/slewing bearing being difficult to rotate or unable to rotate:

[1] The idling of newly purchased products is not flexible. Please check the production date of the slewing bearing. If the weather is cold for a long time (such as more than half a year), it is possible that the temperament such as salt mist is mixed into the raceway, which will cause the rotation resistance to multiply and make the slewing bearing not work well (cold areas, winter is more prominent ) Remedy: If it can run after afterburning and there is no other abnormality, it can be used normally.

[2] After the installation, the operation is not flexible. It may be that the surface of the host machine and the surface of the slewing bearing are not well matched, so that the axial clearance of the slewing bearing after the installation cannot compensate for the deformation of the slewing bearing.

The slewing bearing is in a state of negative clearance, and the rolling elements are rolling Difficulty running in the channel (sometimes accompanied by abnormal noise) or poor meshing of the large and small gears; or foreign objects stuck in the large and small gears.

Remedy: Re-process the plane of the host device to make the device plane meet the requirements; re-adjust the meshing backlash of the large and small gears according to the requirements, especially pay attention to the maximum position of the gear runout; check to ensure that there is no foreign matter in the meshing position of the large and small gears; replace a rotary with a slightly larger clearance support.

[3] The operation is not flexible during use. The sealing strip is damaged, causing foreign objects to enter the raceway (such as poor operating conditions, immersion of dust in the raceway, etc.) the deformation of the isolation block leads to difficulty in operation; there are hard objects or other conditions at the meshing of the big and small gears, such as broken teeth.

Inspection and Acceptance of Slewing Bearings Key Technical Parameters

This article discusses how to diagnose, test and accept slewing bearings after understanding more professional knowledge? What are the main factors for reference, so that the outline can be drawn. The slewing bearing plays the role of bearing, connecting and rotating in the equipment. The important thing in the mechanical equipment is the link device, which must have the ability to support and bear, so it is very important to choose the appropriate standard slewing bearing.

In short, whether it is diagnosing faults, detecting or accepting slewing bearings at the factory, the following technical parameters are verified or required inspection items.

1 The overall dimensions of the slewing bearing, especially if it involves positioning, such as step dimensions;

2 The size of the device hole, the core size in the slewing bearing, the size, number, distribution position of the device hole, wire hole, blind hole, counterbore, thread thickness.

3 Gear parameters, modulus of teeth, coefficient of modification, common normal, tooth surface roughness, commonly known as gear grade

4 Bearing clearance and runout

5 Lubrication system and seals

6 The material, heat treatment, flaw detection and inspection report of the slewing bearing.

Next, you need to understand the topics discussed in depth in this article, as follows:

1. The slewing bearing accepts three forces, namely axial force, radial force and overturning moment. The influence of the thrust of the slewing bearing of the vertical device is relatively large, such as the TBM shield machine, etc., and there is also one that has the largest overturning moment.

2. The diameter of the center circle of the rolling element and the diameter of the rolling element are two important parameters that affect the load distribution of slewing bearings and slewing bearings. Generally, the larger the diameter of the center circle of the rolling element of the bearing, the more uniform the load distribution and the greater the bearing capacity.

The diameter of the rolling element is within a certain range, and the larger the diameter, the greater the bearing capacity. Based on the Hertz elastic contact theory, the static equilibrium equation of the four-point contact ball slewing bearing is established, and the Newton-Raphson method is used to solve it numerically.

Taking a typical type of slewing bearing as an example, the load distribution of multiple sets of bearings is numerically simulated, and the influence of the diameter of the rolling element and the diameter of the center circle of the rolling element on the bearing load distribution is analyzed and studied, which provides a reliable theoretical basis for the shape design of the slewing bearing. .

3. Lubrication system, slewing bearing (slewing bearing) mostly use 2# base pressure lithium grease. Lithium-based grease and base-pressure lithium-based grease are divided into: No. 1, No. 2#3, which have good water resistance, rust prevention, oxidation resistance and lubricating properties, excellent high and low temperature performance and mechanical stability , a multi-action short-lived grease. Its quality index specification is GB7324-94, but it is not suitable to use different grades of grease.

The operating temperature range of No. 1-3 grease: -20℃—120℃. Precautions for use: 1 Avoid mixing with water and impurities during storage and transportation. 2 Do not mix with other greases. 3 Do not use after heating. 4. After use, the remaining grease should be smoothed in the original packaging to prevent oil separation.

How to analyze the quality of lubricating grease:

1. Lighting method 2. Oil drop trace method 3. Oil flow observation method 4. Hand twisting method ; It is a good lubricating oil if it is twisted on the hand and feels no impurities, and it is transparent, clear and free of impurities under the sun; it feels smooth and yellow in color when it is touched by the hand.

4. Bearing clearance, slewing bearing, and slewing bearing clearance are divided into axial clearance and radial clearance according to the different measurement directions. Radial clearance is the basis for the assembly of the inner group, outer ring and rolling elements of the bearing.

It is an important technical quality requirement item in national regulations and other regulations, and is also an important inspection item. From the perspective of bearing application, clearance is also one of the important technical indicators. Whether the bearing can obtain satisfactory performance depends largely on its radial clearance. From the design and use of bearings, the clearance can be divided into: design clearance, original clearance, device clearance and operating clearance.

The clearance achieved after the bearing is assembled is the original clearance, and the clearance changes after the main engine is installed, which is called the installation clearance (or fitting clearance), and the clearance of the bearing during the actual operation is called the working clearance.

When the bearing is working, the temperature rise will change the temperature difference between the internal and external factors, which will reduce the clearance of the device. At the same time, the load will cause elastic deformation of the rolling element and the ring, which will increase the clearance. In the case of a ship, the working clearance is slightly larger than the device clearance. In order to obtain the most satisfactory working performance, an appropriate working clearance should be selected.

5. Speed ​​limit, 1. The running form of the slewing bearing rolling element relative to the raceway wall, sliding along with the rolling, compared with other rolling bearings, the slewing bearing sliding is more serious. Therefore, the slewing bearing is not suitable for high-speed places.

Second, the slewing bearing is a heavy-duty bearing, running at high speed, and the centrifugal force generated by dozens of tons of heavy objects at high speed is huge. Such equipment is classified as high risk.

3. Most of the equipment used in the slewing bearing is heavy-duty lifting and transferring equipment. Therefore, this equipment itself does not need high-speed rotation work.

6. Install bolts and flat washers. The bolts are above grade 8.8, the gaskets are modulated washers, and spring washers are disabled. First of all, when the slewing bearing is connected by bolts and nuts, the bolts are required to be high-strength bolts (grade 10.9).

Secondly, the contact area of ​​the spring washer is not as large as that of the flat washer, and the place with large pre-tightening force is not as reliable as the flat washer. The larger pre-tightening force of the bolt (such as the pre-tightening of bolts of grade 8.8 and above) may cause the spring washer The plastic deformation of the adjacent support surface, in the future use, the preload may appear “relaxation” as the deformation increases.

For slewing machinery, the vibration and overturning moment during operation will be relatively large. If the opening of the spring washer is added, the intensity of the vibration will be aggravated and the slewing bearing ring will be deformed.

In addition, a suitable flat washer can increase the support area, and can prevent the extrusion plastic deformation of the workpiece with insufficient hardness when the bolt is pre-tightened to a certain level, which is conducive to maintaining the reliability of the pre-tightening.

Therefore, slewing bearing requirements prohibit the use of open washers such as elastic washers and the like.

7. The groove pattern and waviness of the slewing bearing are caused by vibration during the grinding process. The greater the vibration during the grinding process, the greater the amplitude. As the amplitude increases, the waviness value of the waviness also increases. The waviness is generally detected with a roundness meter. Roundness measurements show profiles in the spectrum, higher than

The peak-to-valley amplitude of a set of wave numbers within a range of roundness wave numbers is the waviness. Waveforms of 2-15 waves are generally called roundness, and waves of 16-500 are generally called waviness! Slewing bearing waviness generally refers to the microscopic condition of the raceway and rolling element surface. Most of the waviness can be repaired in the ultra-finishing process, while the roundness can only be repaired about 40% or less.

8. The rotation of the slewing bearing, the slewing bearing and the ordinary bearing are very different in the rotational flexibility. The slewing ring/slewing ring bearing is a heavy-duty, low-speed, extra-large bearing, and the initial torque is much larger than that of ordinary bearings.

In addition, the sealing belt and the pressing friction resistance of the inner and outer rings are doubled. The grease filled in the temporarily placed slewing bearing raceway volatilizes and corrodes by air. For these reasons, the frictional resistance of the slewing bearing increases, making it difficult to rotate. However, this requires normal phenomena. After forcibly using the lubricating oil for a day or two, the operation will gradually become more flexible.