What Is a Slewing Bearing?
Slewing bearings are bearings used in the operating parts of construction and civil engineering machinery, especially those parts that operate in a slewing motion.
They are widely used because they have the standard form of a single-row ball bearing and are relatively easy to handle. Slewing bearings have a structure that can simultaneously support single loads and composite loads with respect to moments and other loads.
The moment is the sum of the loads applied to the bearing vertically by the thrust, horizontally by the radial, and the distance between the center of the bearing axis and each point of action of the thrust and radial loads, which are added up to the respective loads.
Slewing bearings are characterized by their high load-carrying capacity. Slewing bearings allow for lower friction in the slewing motion, thus extending the service life of the bearing in practical use.
Applications of Slewing Bearings
Slewing bearings are widely used as bearings in the slewing sections of large machines because they can support combined loads and sustain large loads.
Specific examples of applications are as follows
1. Construction and Civil Engineering Machinery
- Hydraulic excavators
- Attachments
- Cranes
- Earth augers
- Small excavators
- Aerial work vehicle
- Table Lifter
- Special vehicles
2. Equipment Machinery
- Wind power generator
- Parking lot turntable
- Inspection table for automobiles, etc.
- MARUHAN equipment
- Weighing equipment
- Food-related rotating equipment
- Iron and steel-related equipment
- Sludge scraping machine
- Wire drawing winder
- Winches
- Amusement equipment
- Rotating drum for garbage storage
- Revolving stage equipment
3. Precision Machinery
- Industrial robots for equipment
- Polishing machines for semiconductor manufacturing
- Liquid crystal-related polishing machine
- Injection molding machine
- Indexing tables
- Medical equipment
- Radar
Principle of Slewing Bearings
The internal structure of a skewing bearing is the same as that of a standard ball bearing. There is an arc of the inner and outer ring raceways, and the balls are uniformly arranged in a single row inside the arc.
This makes it possible to use even large ball diameters and to design a bearing that is structurally compact but can carry a large load. By machining and mounting gears directly on the inner or outer rings, driven slewing is possible, and the slewing section can be simplified and made lighter.
However, the size of the thrust load that can be supported depends on the size of the balls that are the rolling elements of the bearing. The size of the balls must be determined by calculating the diameter of the balls that is sufficient for the size of the load that needs to be applied.
Other Information on Slewing Bearings
1. Application of Slewing Bearings to Construction Machinery
Slewing bearings are widely used in construction machinery. Slewing bearings enable smooth slewing operation of heavy structures such as power shovels and cranes. The same is true for small cranes used in residential areas.
Slewing bearings are fastened between the upper slewing body and the lower structure with a large number of bolts. As for maintenance, regular greasing of the slewing bearing is necessary. If the grease is depleted, the slewing bearing area will generate abnormal noise and the sliding during slewing will be faulty, making it impossible to perform fine operations.
Resistance during slewing can cause twisting of the entire machine, so regular greasing is essential. As maintenance other than greasing, inspect the slewing bearing fastening bolts on construction machinery for loosening or elongation of the fastening bolts, as these bolts are subjected to large forces during operation.
Continued use of a slewing bearing with loose or stretched fastening bolts could, in the worst case, result in rupture of the fastening bolts or rupture of the slewing bearing, causing a serious accident. To prevent this from happening, it is important to inspect the bolts periodically.
2. Repair of Slewing Bearings
Repairing slewing bearings is a time-consuming and expensive process, depending on the size and the area of use. If the machine is a heavy construction machine, the slewing bearing is located between the upper slewing body and the lower structure, so the upper slewing body must be removed using an overhead crane.
This process is time-consuming and requires workers who are skilled and knowledgeable about the product. Slewing bearings can be prevented from failure through proper product handling and maintenance.