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Bearings are used in machines and mechanical units as guide elements to enable, guide and control movements.

They are crucial for the smooth operation of mechanical systems, as they reduce friction, absorb forces and increase the precision of movement.

Below you will find the basic functions and different types of bearings, their design and specific applications, as well as an overview of maintenance and care:

Basic functions of bearings as guide elements:

Bearings perform various tasks in machines to ensure precise movements and reliable operation:

1. Bearings minimize direct contact between moving parts, which reduces friction and therefore wear and energy consumption.
2. Bearings are designed to absorb and transmit forces (e.g. axial and radial loads). This protects the other components and enables efficient force distribution.
3. They enable and guide linear or rotary movements. Bearings are therefore a decisive factor for the precision and stability of mechanical processes.
4. Bearings fix the components in their intended position and prevent unwanted movements or vibrations that could impair the system.

Types and design of bearings:

Bearings come in a variety of designs that differ in their construction and application:

1. Plain bearings:

Plain bearings are a widely used type of bearing that, unlike rolling bearings, do not contain any rolling elements. Instead, movement is achieved by two surfaces sliding against each other. They are simple in design and inexpensive, but can be the better choice for certain applications.

Structure of plain bearings:

Bearing bush or sliding surface: The main component of a plain bearing is the bearing bush or sliding surface on which the axle or shaft moves. These bushes are often made of wear-resistant material such as bronze, plastic or special plain bearing materials.
Bearing shell: Plain bearings can also consist of an inner and outer bearing shell that protects and encases the sliding surface.
Lubrication: Many plain bearings require lubrication to reduce friction and extend service life. However, there are also self-lubricating plain bearings that use special material mixtures.

Types of plain bearings:

1. Radial plain bearings: These are used to absorb radial forces (forces acting perpendicular to the axis) and are used in applications with slowly rotating or oscillating movements.
2. Axial plain bearings (thrust bearings): These plain bearings absorb axial forces (forces acting along the axis) and are often used in screw spindles or in slowly rotating shafts.
3. Flat plain bearings: These plain bearings are used to support large flat contact points, such as in presses or heavy machinery.
4. Self-lubricating plain bearings: These types of bearings do not require external lubrication and are made of material mixtures that offer permanent sliding properties, such as PTFE or special plastics.

Application of plain bearings:

Plain bearings are ideal for applications with high loads and low speeds.

1. Automotive industry:
In vehicle suspensions, engines (e.g. connecting rod bearings and camshaft bearings), gearboxes and brakes, where high loads occur.

2. Construction and agricultural machinery:
In applications where simple and robust bearings are required, such as in excavators, tractors and cranes, as plain bearings can cope well with dirt and loads.

3. Heavy industry:
In presses, rolling mills and turbines, where high forces act on the bearing and harsh environmental conditions often prevail.

4. Hydroelectric power stations:
For the bearing support of water turbines, as plain bearings can support high loads and can be used well in water environments with special lubricants.

5. Electric motors and small machines:
In household appliances or small electric motors where noise and maintenance should be reduced.

2. Magnetic bearings:

Magnetic bearings use magnetic forces to support and stabilize an axle or shaft. As there is no contact between the moving parts, there is virtually no friction, which makes magnetic bearings very durable and virtually eliminates wear.

Structure of magnetic bearings:

Magnets: Strong permanent magnets or electromagnets ensure that the shaft is levitated. The shaft remains in position due to the magnetic force, without mechanical contact.
Bearing control (with active magnetic bearings): In active magnetic bearings, the position of the shaft is monitored and corrected using an electronic control system. Sensors detect changes in position and adjust the magnetic force to stabilize the shaft.
Power supply: Active magnetic bearings require a constant supply of energy to power the electromagnets and the controller.

Types of magnetic bearings:

1. Passive magnetic bearings: These bearings use only permanent magnets and do not require a controller. However, they have limited stability and are often only suitable as additional bearings.
2. Active magnetic bearings: These bearings use electromagnets that are actively controlled. This allows the position to be precisely controlled and greater stability to be achieved.
3. Superconducting magnetic bearings: These high-tech bearings utilize the property of superconductors to exclude magnetic fields and thus enable almost perfect freedom from friction.

Application of magnetic bearings:

Magnetic bearings are used in applications where maximum precision and low friction are required.

1. High-speed rotors:
In gas and steam turbines, e.g. for power generation, as magnetic bearings enable high rotational speeds and offer precise, friction-free movement.

2. Medical technology:
In MRI (magnetic resonance imaging) machines, where non-contact and low-vibration bearings are required to ensure image quality and patient safety.

3. Space and satellite technology:
For gyroscopic systems and rotating components, as magnetic bearings can operate in a vacuum and do not require lubrication.

4. Laboratory and measurement technology:
For applications such as high-speed centrifuges, where extremely low friction and high precision are required.

5. Precision mechanical engineering:
In very precise processing machines and optical instruments where minimum wear and maximum accuracy are required.

3. Fluid bearings:

Fluid bearings use a thin layer of fluid created by pressure or rotation to separate and support the moving parts. This layer can consist of oil, water or other liquids. Friction is minimal here, as the parts move separately through the liquid.

Structure of fluid bearings:

Bearing housing and bearing surfaces: The bearing surfaces are often made of robust material and surrounded by a housing that holds the fluid and stabilizes the components.
Fluid layer: Movement of the shaft or external pumping creates a pressurized layer of fluid that supports the weight of the shaft or components.
Seals: The seals are required to keep the fluid in the bearing area and prevent leakage.

Types of fluid bearings:

1. Hydrodynamic bearings: the fluid layer is created by the rotation of the shaft, which thus creates the necessary pressure distribution.
2. Hydrostatic bearings: Here the pressure layer is generated externally by pumps. This enables a high load-bearing capacity even at low speeds or at standstill.

Application of liquid bearings:

Fluid bearings are well suited for high-speed applications and where low friction and noise are desired.

1. Pumps and turbines:
In water or oil pumps and hydroelectric plants, as liquid bearings provide constant lubrication and can handle high loads and speeds well.

2. Heavy loads in industry:
In large industrial machinery and rolling mills, where high loads and strong vibrations occur. The fluid layer also dampens vibrations and reduces wear.

3. Ships and submarines:
In ship propellers and submarine turbines, which are often operated in water or in a water-like environment, as fluid bearings work effectively under high loads and in humid environments.

4. Power plants:
In large generators and turbines to ensure reliable, low-wear movement and extend the life of the machinery.

5. Aerospace industry:
In jet engines to ensure reliable, low-friction bearing support at high temperatures and speeds.

4. Air bearings, aerostatic or aerodynamic bearings:

A special form of liquid bearings are air bearings, which use a thin layer of air as a separating medium instead of liquids. Air bearings are ideal for applications that require extremely low friction and high precision, such as optical devices or microelectronics.

Structure of air bearings:

Bearing surfaces: Bearing surfaces are often made of special materials that allow minimal friction and offer high stability.
Air supply system: An external system pumps the air into the bearing so that a thin layer of air forms between the moving parts.
Seals: Seals are also necessary to keep the air in the bearing area to maintain even air pressure.

Types of air bearings:

1. Porous air bearings: air exits evenly from a porous material, forming a stable layer.
2. Nozzle air bearings: Here the air is fed through a series of small nozzles to create a homogeneous layer of air.

Application of air bearings:

Air bearings are used in high-tech applications where maximum precision and low vibration are important.

1. Semiconductor and electronics manufacturing:
In precision manufacturing equipment, such as for the production of computer chips, as air bearings provide vibration-free, extremely precise motion control.

2. Measuring and testing equipment:
In optical measuring devices and microscopes where vibration and mechanical friction could interfere, such as in laser interferometers.

3. Medical devices and laboratory applications:
In analytical and testing equipment where friction-free motion is required for precise results, such as in centrifuges and blood analyzers.

4. 3D printing and additive manufacturing:
In high-precision printers that require tiny layer resolutions to maximize the quality and detail of models.

5. Optical instruments and telescopes:
In high-precision optics and telescopes that require vibration-free movement to ensure high-resolution images.

In addition to rolling bearings, plain bearings, magnetic bearings, fluid bearings and air bearings each offer unique advantages in different applications. The selection of the right bearing depends on the load, friction, precision and maintenance requirements.

Maintenance and care of bearings:

Regular maintenance is crucial to ensure the function of bearings as guiding elements and to extend their service life:

• Sufficient and regular lubrication reduces friction and protects against wear. Depending on the application, oil or grease is used, whereby the lubrication intervals vary.
• Dirt and foreign particles in the bearing can increase friction and lead to damage. Bearings in dusty or dirty environments should therefore be well sealed or cleaned regularly.
• Bearings must be checked regularly for signs of wear and replaced if necessary. Modern sensors can measure vibrations and temperatures to provide early warning of problems.

As guide elements, bearings are an indispensable component of mechanical systems. They guide and support movements, reduce friction and increase the precision and stability of machines and vehicles.

Below is an overview of the most important points to consider when purchasing bearings:

When purchasing bearings, there are a number of important aspects to ensure that the bearing is ideally suited to the intended application. The right choice of bearings can improve the performance and service life of machinery and equipment and reduce maintenance and downtime costs.

• Decide whether a plain bearing, magnetic bearing, air bearing or fluid bearing is suitable based on the specific requirements of the application.
• Linear motion or rotary motion? For rotary motion, plain bearings, magnetic bearings or fluid bearings are often more suitable, while for linear motion, plain-magnetic or air-bearing linear bearings should be chosen.
• Consider whether the bearing has to bear high radial and/or axial loads.
• The bearing must be able to support the maximum expected dynamic load (movement) and static load (at rest).
• Make sure that the bearing is designed for the specific load distribution (axial, radial or combined loads).
• In certain applications, the bearing should be able to safely withstand a certain overload.
• Each bearing has a maximum recommended speed at which the operating temperature and performance are still within the safe range.
• Ensure that the bearing operates reliably in the intended ambient temperature, especially at extreme temperatures (e.g. in high-temperature systems).
• If high speeds are reached, additional cooling or special lubrication may be required.
• The radial or axial clearance of a bearing should meet the requirements. Too much clearance can lead to instability and vibrations, while too little clearance increases wear.
• Depending on the application, a higher precision class may be required, especially in machines that require high accuracy and low tolerances.
• Depending on the application (e.g. stainless steel for humid environments or corrosive conditions). Bearings with special coatings are often protected against corrosion and wear.
• Sealed bearings prevent dirt and moisture from entering the bearing interior and shortening the service life.
• Ensure that the material is compatible with the intended lubricants.
• Choose between grease-lubricated and oil-lubricated bearings or even maintenance-free bearings (e.g. with solid lubricant).
• Choosing a low-maintenance or maintenance-free bearing can reduce maintenance requirements and the associated costs.
• Especially for high or low temperature applications, the lubricant must be suitable for the environment.
• Some bearings are easier to install than others. Handling should be taken into account, especially when frequent replacement is required.
• Standard bearings are often more readily available and less expensive than specialized bearings. It is advantageous to rely on standardized bearing sizes and types.
• Check whether special tools or adaptations are required for installation.
• Pay attention to the specified service life and consider whether this matches the operating requirements.
• Consider environmental conditions such as humidity, dust, vibrations or corrosive elements as they can affect the service life.
• The expected service life can be checked using calculations or manufacturer specifications, especially for critical applications.
• A cheap bearing can save costs in the short term, but may cause expensive failure costs. In the long term, high-quality bearings are often cheaper.
• Especially in applications where the machine must avoid long downtimes, the availability and fast delivery time of bearings is important.
• Pay attention to the manufacturer's reliability and quality guarantees.
• In areas such as the food industry or medicine, special requirements may be placed on environmental friendliness.
• For applications in close proximity to people, such as household appliances or medical technology, a low noise level can be crucial.
• For applications with high safety or hygiene requirements (e.g. in aviation or food processing), certified bearings that meet certain ISO or DIN standards should be selected.

Careful analysis of the bearing requirements and consideration of the environmental conditions, loads and maintenance needs can extend the bearing's service life and significantly improve the efficiency of the machine or system.

Bearings can be purchased from various suppliers. Comprehensive information about manufacturers and suppliers of Bearings from all over the world can be found on Exportpages.