Installing rolling element bearings on OEM production lines has always depended on the skill and experience of the installer. But new bearing designs and improved installation methods offer more reliable alternatives.
When rolling element bearings are required in manufactured products, an installer on the production line is often responsible for final assembly of the bearing, and for greasing and sealing it. This assembly task includes adjusting the bearing carefully so that its internal clearances — radial and axial distances between its inner and outer rings — meet the application requirements.
At the end of the line, workers test the product. In many plants, testing consists of an experienced worker listening closely to the product as it operates. Often, this is the only way to check if bearings and other components were installed properly.
Today, new bearing designs, improved installation tools, and monitoring devices offer manufacturers more reliable alternatives to traditional installation methods. These new methods take less time, reduce warranty costs, and improve the performance of the end products.For example, pre-adjusted, pre-lubricated unitized bearings greatly simplify the installation process, decreasing the risk of costly errors.
The use of unitized bearings — self-contained, pre-adjusted units — is increasing. This is especially so in the automotive industry, where unitized wheel bearing assemblies, called hub units, have become virtually standard in domestic cars.
Previously, assembly line workers collected and assembled wheel bearing components — inner and outer rings, grease, seals, spacers, and lock nut. They were responsible for adjusting bearings and lubricating them with the correct grease in the right amount. Errors could occur at each step of this procedure.
Bearing designers are working to integrate related functions into the hub unit. For example, one type of hub unit, which is typically used in driven wheel applications, also transmits power to the wheel via a splined inner ring bore.Other hub units incorporate a wheel speed sensor, an important part of the anti-lock braking system. Currently, in most vehicles, the sensor is a discrete unit that is mounted separately.
The auto industry is not alone in reaping the benefits of bearings with integrated sensors. Other companies, wanting to prevent machinery breakdowns, use sensor bearings to obtain feedback on critical machine functions, such as speed, load, force, and temperature.
Installers use four basic methods to mount bearings on shafts.
Mechanical mounting-which uses physical force. The other three methods rely on newer techniques to increase reliability and ease mounting of large bearings.
Temperature mounting-which uses heat to expand the bearing and make it easier to mount.
Hydraulic mounting-which uses hydraulic pressure to impart mounting force.
Oil injection method-which introduces a pressurized oil film between the shaft and inner ring to reduce frictional resistance.
Production line innovations aren’t limited to new bearing designs and improved installation tools. Condition monitoring devices are also gaining increased acceptance as a way to ensure proper bearing installation.