Types Of Bearing

Fig.1 Type of Bearings

Bearing is a mechanical component that carries load, aligns motion and reduces friction between two moving parts. Today we will explain the differences between all types of bearings.

Bearing is mainly classified into two:

●        Rolling Bearing/Anti Friction Bearing

Fig.2 xiros® Ball Bearing - Rolling Element Bearing

Rolling bearing has a rolling element such as a ball, roller, sphere or needle to transmit load from a moving to a stationary part. Rolling bearing consists of two rings (inner and outer ring), rolling elements and separators. The rolling elements are placed between the two rings’ raceway and groove and the separators are used to hold the rolling elements apart.

Rolling bearing is also known as anti-friction bearing because of its low coefficient of friction. Rolling bearing replaces sliding with rolling which minimizes friction and resistance. Furthermore, it minimizes fluid or lubrication requirements.

Rolling elements can come in different shapes: Ball and roller. Each is designed to handle different load requirements. Ball shape makes point contact and can handle both radial and axial load for small weight/load. It is also the most common type of rolling element; Roller shape provides a greater contact area than ball hence it can carry more load. However, it can handle little to no axial load.

The rolling element can be configured to improve bearing’s load handling capacity and feature. Below are the summary of the different types:

Rolling Element

Type of Bearing

Description

Ball

Radial Ball Bearing

Radial ball bearing is the basic ball shaped rolling bearing that can hold radial and axial load

 

Angular Contact Ball Bearing

This ball bearing has a certain contact angle which improves thrust load. The contact angle usually is less than 40o. The larger the contact angle, the larger the thrust load capacity. However, this type of bearing can only support thrust load in one direction.

 

Double Row Angular Contact Ball Bearing

Double row angular contact ball bearing combines two angular contact ball bearings back to back to increase the radial load capacity and support bi-directional axial load.

 

Axial Ball Bearing

The axial ball bearing is designed to take more thrust load at low speed. The balls are sandwiched between two ring-shaped plate

 

Axial Angular Contact Ball Bearing

A contact angle is introduced to axial ball bearing to improve load capacity and support bidirectional load

Roller

Cylindrical Roller Bearing

Instead of balls, cylinders are used as the rolling element. Cylinder roller has a better load carrying capacity than ball due to its larger surface area. It has very low thrust load capacity.

 

Needle Bearing

Needle bearing is a thin cylinder with excellent radial load capacity. It is designed for application with limited space

 

Tapered Roller Bearing

Tapered roller introduces contact angle to improve the bearing’s thrust load capacity. The higher the contact angle the higher the thrust load capacity.

 

Spherical Roller Bearing

Instead of a cylinder, spherical roller bearing uses spheres as its rolling element. Sphere roller bearing can self-align when there is a misalignment on the bearing.

 

Axial Cylindrical Roller Bearing

Axial cylindrical roller bearing is designed to carry higher thrust load with 2 plates supporting the cylinder.

●        Plain Bearing or journal bearing

Fig. 3 iglidur® Polymer Plain Bearing

Plain bearing is considered as the most basic form of bearing with just a round plate or tube. Different from rolling bearing, plain bearing makes sliding contact instead of point contact and has a higher surface contact area and with a higher load-carrying capacity. Plain bearing is also lighter and relatively cheaper than rolling bearing.

Plain bearing is made of layers of materials with different functions and properties. The layer is softer than the shaft for sacrificial purposes as it is more economical to replace the bearing instead of the shaft. Soft layer also allows contaminants to be embedded into the bearing instead of the shaft.

Plain bearing uses lubrication to prevent metal to metal contact between the shaft and the bearing. Lubrication fills the gap between the bearing and the shaft to prevent friction that can lead to wear and failure. Based on the different lubrication method, plain bearing can be classified into 3 types: hydrodynamic bearing, hydrostatic bearing and journal bearing.

●        Hydrodynamic Bearing

Hydrodynamic bearing depends on a low-friction surface called wedge to avoid the metal to metal contact. Wedge is formed when the lubricant gets thicker because of high rotating shaft speed. Theoretically, hydrodynamic bearing can run forever due to no metal to metal contact operation. However, a certain shaft speed needs to be maintained in order to keep the surface formed, therefore metal to metal contact still occurs during start up and shut down phase.

●        Hydrostatic Bearing

Hydrostatic bearing addresses the issues of hydrodynamic bearing during its startup and shut down phase. Hydrostatic bearing uses pressurized oil or lubricant to give the lifting force required to push the shaft from contacting the bearing. Similar to hydrodynamic bearing, lubrication is required to prevent metal to metal contact. The downside of hydrostatic bearing is its high auxiliary cost from pump’s installation and maintenance cost.

●        Dry Plain Bearing

Dry plain bearing is another type of plain bearing that instead of metal is made from polymer, additives and solid lubrication. Dry plain bearing solves the problem of both hydrodynamic and hydrostatic bearing which require constant lubrication to operate. Dry plain bearing is suitable for applications that with clean and hygiene requirement.

igus®  drytech® bearing technology uses special iglide material to create lubrication-free bearing. Our bearings have been used in various industries from packaging, pneumatic, automation, healthcare. To learn more about igus drytech bearing, check out our website here.