How to select slewing bearing

Select suitable slewing bearing

Slewing bearings are usually used for their ability to transfer relatively high loads, which is the most important application. However, there are other potential application requirements that may have a significant impact on the selection of suitable slewing rings, which should be fully considered in the selection process. These considerations include speed, pollution prevention, accuracy, friction resistance, and the temperature range of the operating environment.

Procedure for selecting slewing ring

This white paper outlines the nine steps to select the right slewing ring for a particular application. Note that these guidelines apply to "normal swing applications" and are defined as applications that meet the following conditions:

·Vertical axis of rotation

·Compression thrust and moment loads (see Figure 1)

·Radial load less than 10% of thrust load

·Occasional oscillation or intermittent rotation of pitch line speed (500 FPM for single row bearings and 300 FPM for multiple row bearings)

·Between + 20 ° C and - 60 ° f (- 29 ° f)

·The mounting surface shall be reinforced and machined according to the bearing manufacturer's standard

·Correct installation

·Regular lubrication

·Periodically confirm the required bolt tension

If your product is not "in normal use," consulting the bearing supplier early in the project can help ensure success.

图1 
压缩推力和力矩载荷

Step 1

Determine the requirements of your application in terms of load, speed, accuracy, torque, environment, coating, mounting arrangement and lubrication. Kaydon's specification data sheet lists more common requirements. Early consultation with your bearing manufacturer will help to ensure that bearings are selected that meet the necessary features of your requirements.

Step 2

Determine all maximum bearing loads and ensure that all dynamic and static loads applied to the bearings are included.

Consider all forces applied to bearings and gears - not only at rated and operating loads, but also during the following periods:

·Extreme weather conditions

·Influence or test

·Assembly or disassembly

·All other cases

These loads must be reduced to forces acting on the center of the bearing. See Figure 2.

图2 
作用在轴承上或轴承周围的合力

Step 3

Multiply the resultant bearing force by the applicable service factor (SF). See Table 1 for usage factors for common applications,

The application service factor is based on many considerations. The main considerations are the frequency of use of high and normal loads and the possibility of extreme or impact loads. These factors may be replaced by customer specifications, finite element analysis (FEA) or regulations of certification bodies.

If the expected devices and applications are not shown in Table 1, select comparable applications for initial sizing. If in doubt, consult the bearing manufacturer.

*不包括卷取机/开卷机

Step 4

If an integral gear is required, determine the required gear capacity. As with bearing loads, consider all conditions that may produce potential gear loads. Examples include static load, dynamic load, tilt load, and overload test. Also consider the duty cycle in each case.

Step 5

Considering the position of the pinion and the gear, determine the preferred mounting method. Consider the installation and continuous maintenance requirements of bearings and retaining bolts. The slewing bearing can be designed to be suitable for various installation methods.

For the basic configuration example of slewing ring, please refer to figure 3 to figure 6, which can be adjusted according to the requirements of specific application. The mounting structure shown is for illustration only.

图3 
The pinion is connected to the outer ring support and the upper structure is supported by the inner ring. Guards on external seals and bolts prevent contamination under extreme conditions. Display by bolt arrangement.

图4 
The inner ring with through bolts supports the upper structure through the pinion. The outer shield protects the gear teeth on the outer ring and is supported by bolts on the substructure.

图5 
The gears are connected to the superstructure supported by the outer ring. The gear position on the inner ring prevents harsh external conditions. Shows threaded bolt arrangement.

图6 
The pinion is connected to the lower structure of the support inner ring. The outer ring of the gear supports the upper structure. Through the bolts used on the inner ring and the bolts on the outer ring.

Step 6

View available bearing types and cross sections. Figure 7 shows some slewing ring designs.

图7 

RK系列

MT系列

XR系列

TR系列

Step 7

A preliminary selection is made by comparing the combined working bearing force (including service factor (SF)) and the rating curve of the bearing.

In order to give the resultant force lower than required for all bearing applications.

Ensure that all extreme load conditions are below the rating curve of the bearing. The service factor is not included if the extreme load condition is static and only occurs more than once during the service life of the bearing. Otherwise, it includes service factors.

The maximum rated thrust of the bearing shall exceed 3 times of the maximum working thrust of the bearing, regardless of the torque under the condition. The standard is due to concerns about the rigidity of the support structure and the ability to distribute the load appropriately around the bearing diameter. If the required bearings do not meet this standard, contact the bearing manufacturer for assistance.

Multiple bearings can meet the required rated load.

图8 
多种轴承类型的Z大额定曲线

Step 8

Check gear size, quality and rating.

The gear rating (Fz) of the chart represents the maximum allowable tangential gear tooth load for normal slewing bearing applications. For more information, see page 21 of kaydon catalog 390.

Step 9

Finally, make sure that the bearing you choose meets all your design requirements. It can help to obtain preliminary data. Consult bearing and other parts manufacturers and submit complete specification data sheet to bearing manufacturer to confirm correct bearing selection. Ultimately, the responsibility for choosing the right bearing lies with the equipment designer.

conclusion

Like all bearings, slewing rings serve as a connection between two adjacent structures, allowing the rotation and transfer of load between them. In addition, slewing bearings usually include features for simple and rapid attachment to those adjacent structures, and features that facilitate mechanical rotation of one ring and its adjacent structure relative to another.

Slewing bearing is traditionally considered to be large diameter, heavy section, low precision bearing. But today they are also easy to obtain apertures as small as 50 mm, making them ideal for robotics, radar bases and other precision applications.

The use of a single large diameter bearing allows wiring and piping to pass through the bore of the bearing. This simplifies the overall design, helps protect components and improves appearance.

The key is to choose the right slewing ring. Bearing in mind all relevant design requirements and with the help of the bearing manufacturer, a slewing ring that meets or exceeds all application requirements can be specified.