Thin Section Angular Contact Bearings for Industrial Robots

Bearings for industrial robots must have a long life. To achieve that, they must have a high rigidity and excellent performance.

Angular contact ball bearings can bear combined radial and axial loads. They are also able to operate at higher speeds with better endurance.

These types of bearings must be fitted as pairs. Oftentimes, duplex bearings are used to handle heavy axial loads.

Axial Load Capacity

The axial load capacity of a thin section angular contact bearing is determined by the amount of force transmitted between the inner and outer rings through the contact angle. This load capacity increases as the contact angle increases.

Kaydon Reali-Slim type A angular contact bearings have sufficient diametral clearance to provide a substantial contact angle and support axial loads. These bearings are designed for pure axial loads or combined radial and axial loads. They should be mounted opposed to each other so that they maintain the required contact angle and support reversing thrust loads.

These bearings have a counterbored outer race and a contact angle of 35deg. They have a higher axial load capacity than single-row angular contact bearings and are well-suited for reversing axial loads. These bearings must be used in pairs and can carry reversing axial loads and moment load. However, excessive end float can cause roller to track misalignment and reduce life.

Radial Load Capacity

Unlike standard deep groove bearings, the cross section of thin section angular contact bearings do not increase as bore size increases. This allows for greater use of space within an application and reduces overall system weight.

Like other ball bearings, angular contact bearings can support radial loads. They also can accommodate axial thrust loads. To achieve high axial load capacity, angular contact bearings incorporate shoulders on the inner race to provide increased axial load resistance. They are available in either single-row or duplex pairs, with the option to mount them back-to-back for applications that require axial loads in both directions.

A duplex pair of angular contact bearings with a light preload was used in an aircraft turret azimuth drive assembly to provide low torque and combined load capacities in a compact envelope. These bearings provided stiffness, reduced weight and corrosion resistance. They were made from 52100 chrome steel and 440C stainless steel with pressed steel cages.

Static Capacity

The static load capacity of a thin section angular contact bearing depends on the type of bearing, the application and the lubricant. It is also influenced by the operating temperature and ambient conditions.

Axial thrust capacity is a function of the contact angle between the balls and the raceways, which determines the amount of resistance to axial loading. Thrust ratings are usually 2.5 to 3 times the radial rating. Angular contact bearings can cope with heavy axial loads but only if they are mounted back-to-back or in combination with a radial bearing.

Thin section angular contact bearings have big enough radial clearance to produce a substantial contact angle, which resists axial loading in both directions. However, they should always be installed in pairs when supporting double direction axial load (as DF or DB), moment load or reversing axial load. Typical duplex bearing arrangements include face to face, tandem and back to back installations.

Dynamic Capacity

A semiconductor automated test system required a bearing to take combined radial and axial loading. A duplex pair of angular contact RBC Thin Section ball bearings was designed with toroid separators for the application.

When significant shaft deflection and/or housing distortion occur in some applications the basic dynamic radial load rating can be significantly reduced. Computer analysis and internal design can help minimize these effects.

In some cases the actual load capacity can be much higher than the basic dynamic radial load rating. This can be achieved by applying a relatively light bearing preload. Excessive preload, however, causes a loss of stiffness and a breakdown in lubrication. A consult with your RBC Sales Engineer to determine if this method can be applied to your specific application. It will often result in a lower cost, smaller machine size and improved reliability.