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How NOT To Kill A Bearing

POSTED 12/13/2023  | By: Emmet Cole, A3 Contributing Editor

In pure engineering terms, a bearing is defined as any mechanical component that enables parts to move and/or rotate while reducing friction between them. Simple definitions, of course, hide a wealth of complexity. 

The humble ball bearing, for example, is commonly found in motion control and automation applications. In its “deep groove” variety, ball bearings play a key role in the electric motors and gearboxes found in AMRs, AGVs, and industrial robot arms. 

Meanwhile, roller bearings are known for their ability to handle bigger loads and are often used in conveyors, automotive manufacturing equipment and CNC machines. Slewing bearings are even bigger and can be found in heavy-duty turntables and wind turbines. 

There are precision bearings for high-speed measuring applications. Magnetic bearings for extremely specialized automation tasks. There are bearings made of thin films of pressurized air. And bearings that self-align. 

Not all bearings are spherical in shape. And not all bearings roll: some, such as dovetail bearings, slide. 

Given the wide variety of bearings available and the enormous range of applications they are used in, selecting the right bearing for your application is probably not as simple and straightforward a process as you might imagine. 

If you get the basics right and avoid common pitfalls, your bearing will perform effectively for as long as it’s meant to. And if you don’t…

CW Bearing’s ‘thin section deep groove ball bearings’ are found in automation applications from AGVs and AMRs to conveyors and robotic arms. Credit: CW Bearing

“Good bearings don’t die,” says Kyle Weyers, director industrial sales at leading bearing manufacturer CW Bearing USA: “They are murdered. It’s extremely uncommon to see a premature bearing failure, unless mistakes have been made.“ 

Start strong with detailed specifications 

Make sure to consider the full range of factors that will impact your choice of bearing. Understanding the application and its operating environment is a good start. 
“Failure to spec out your bearing requirements correctly is a common cause of bearing failure. Beyond the physical properties of the bearing, it’s important to consider the specifics of the application it will be used in, including environmental conditions,” explains Weyers. 

Pay attention to the radial and axial load capacity of the bearing and how that relates to your application requirements. Determine clearance requirements; that is, the amount of error allowed when the bearing moves in its constrained motion. Account for tolerance fits — too tight a fit makes the bearing harder to assemble and could shorten its useful life. 

Consider the operational speed and duty cycle requirements of your application to avoid risk of excessive heat and reduced bearing life. Define your size and space restraints. Understand the environment the bearing will be operating in. 

PI USA’s large rotary air bearing for high loads is designed to provide extremely low wobble and eccentricity. Credit: PI USAKnow your limits 

Several leading bearing manufacturers provide online tools to help you with the bearing specification and selection process. But if you lack experience or you have any questions, it’s a good idea reach out to manufacturers early, says Beda Espinoza, product manager at PI-USA, a leading manufacturer of motion control and automation systems. 

“Unless you have designed bearings into motion systems for many years and have the experience, I think it’s always a good idea to consult with the bearing manufacturer. Make a selection from catalog specifications and guides provided by the manufacturer, and then talk to their application or tech support folks. They can evaluate your choice and provide other insights,” explains Espinoza.  

These insights go far beyond understanding catalog specifications. For example, if lifetime, accuracy, cleanroom compatibility or minimized friction are of concern, Espinoza recommends looking into air bearings rather than mechanical bearings.

“Bearing manufacturers have a wealth of knowledge related to bearings and their applications. From highly dynamic systems and extreme clean-room deployments to lubrication strategies and high energy considerations, a good bearing manufacturer will be familiar with these challenges and be able to guide you through the process.”  

The lifetime of a bearing is an important consideration that tends to be overlooked, Espinoza notes, adding: “In general, manufacturers’ data on bearings is backed by extensive internal and independent testing, so make use of this readily available information.” 

Bearing manufacturers also have access to tools and data that aren’t necessarily publicly available, says CW Bearing’s Weyers.

“For some applications, selecting the right bearing can require complex calculations and a deep understanding of the bearing’s internal geometries. Talking with our application engineers and design engineers early in the process will ensure that the bearing you select is optimized for your application.” 

Don’t neglect safety

Safety considerations go beyond the basic load capacity, speed limit, and environmental conditions specified early in the bearing selection process. 
Pay attention to material compatibility, for example, to prevent premature wear or failure. Understand the lubrication requirements, if any, and develop a regular maintenance and inspection schedule.  Ensure that the bearing is properly sealed and protected from environmental hazards. 

For some applications, you’ll need to pay particular attention to ensuring that the bearing is compatible with the overall safety systems of the machine, such as emergency stop mechanisms and overload protection devices. 

This planar air bearing on granite from PI USA can be used in applications that require large XY motion ranges. Credit: PI USA

Think ahead 

Make sure your facility is set up to safely handle and store bearings in a clean environment. Avoid touching the bearing surface and keep them in their original packaging until you’re ready to use them. 

Eventually, it comes time to install and test your bearing –a process that requires specialist equipment such as bearing drivers and press fits. Highly specialized bearings can require equally specialized installation and testing equipment, so, be sure to factor this into your decision-making process where appropriate.