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Let it slide:
The ins and outs of slewing ring bearing technology

By Tom Miller, iglide Bearings Unit Manager, igus

If you've ever been in the market for a slewing ring bearing, you may have found the number of available options to be somewhat limited. Roller slewing rings have been the only choice for rotating or turntable applications, but for your next project you might want to consider a new technology: sliding-element slewing ring bearings.

igus' PRT sliding slewing ring bearings possess low moisture absorption and are corrosion resistant and completely maintenance free. You can get more specs on PRT sliding slew ring bearings and see a video of the bearing in action by clicking here. The video link is on the right-hand side of the page.

 

 

 

 

Sliding slewing ring bearings can be considered a middle-ground solution. While they don't offer the same level of precision or load capacity that a rolling element does, sliding slewing ring bearings do offer a high-performance, lower cost alternative. I would also estimate that seven out of every 10 people using high-priced rolling elements chose them simply because they believed they were the only option available, not because the application required them.

Features
Most roller bearing designs use metal, stainless steel, or ceramic balls to maintain the separation between the moving parts of the bearing. In contrast, sliding slewing ring bearings use self-lubricating, low-friction polymer sliding elements in place of balls.

Where roller bearings require constant lubrication and regular maintenance, sliding slewing ring bearings are a "fit-and-forget" solution, as they do not require any additional lubrication or scheduled maintenance. Thanks to their lubrication-free properties, they won't contaminate environments or seize in applications with dirt or dust, unlike roller bearings.

The plastic sliding elements and hard anodized-aluminum finish of sliding slewing ring bearings possess low moisture absorption and corrosion resistance and so do not require a cover or seal around the slewing ring when used in wash-down applications. Sliding slewing ring bearings can also be used in medical and lab equipment, solar panels, food processing and packaging machines, and many more.

iglide PRT slewing ring bearings use self-lubricating, low-friction polymer sliding elements.

 

 

Performance factors
Load capacity. igus' line of sliding slewing rings can handle dynamic loads up to 20,000 lb in the axial direction and dynamic radial loads up to 6,000 lb, which makes them ideal for applications with low to moderate loads. Roller bearings are best for applications handling exceptionally high loads.

Speed and rotation. Sliding slewing ring bearings operate at a maximum of 200 rotations per minute (rpm), while a rolling system can deliver up to 500 rpm. Clearly, this is a large difference, but for the majority of applications a sliding slewing ring can easily handle the job. On the rare occasion that an extremely high number of rpms are required, a roller bearing would be the better solution. They are the best choice for fast, continuous rotations, while sliding slewing rings are ideal for applications with inconsistent movement at slow to moderate speeds or for fast speeds with very low loads.

Vibration absorption. Sliding slewing ring bearings have excellent vibration-dampening ability. When tested, our PRT slewing ring bearings outperformed roller bearings in atmospheric conditions at 5 Gs. The vibration caused the balls in the roller bearing to fly out, while the sliding slewing bearing absorbed the vibration and remained completely intact.

Temperature. Both roller bearings and sliding slewing ring bearings can be used in extreme temperatures. The difference is that sliding systems (with the plastic elements and optional stainless rings) can be used in applications reaching 392 degrees F, and the maximum temperature that a roller bearing can endure is determined by the particular metals it's made of.

Price. Choosing products that deliver a superior performance is a priority, but cost is also an important consideration when deciding on any component. Sliding slewing rings offer superior quality in comparison to turntable-style slewing rings, but they cost a lot less than high-end roller bearings, which are not necessary for many applications.

Semiconductor handling and transportation system uses maintenance-free PRT slewing rings.

 

 

Conclusion
Sliding slewing ring bearings are a low-cost replacement for expensive roller bearings. However, I always consider all the parameters, such as environment, loads, speeds, and rpms, before recommending the right type of bearing for your application.

Tom Miller is interested in your thoughts about sliding slewing ring bearings versus other bearing designs. You can contact him at tmiller@igus.com.

Want more information? Click below.

igus

Published September 2012

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