The Limits of Metal Ball Bearings & Why Plastic Might Be Better

May 21, 2020 Patrick Czaja

Ball bearings made of metal are instrumental in mechanical and plant engineering. However, there are industries where conventional metal ball bearings have their limits, such as within the food industry and medical technology. Since the hygiene factor plays a major role within these sectors, lubricants are a no-go. Therefore, plastic ball bearings enter into the spotlight, which is where igus® steps in and manufacturers plastic ball bearings from innovative plastic materials. This means that all of our ball bearings are absolutely grease-free and pose no hygiene risk.

The ball bearing evolution

When the French cyclist, Jules Suriray, invented the ball bearing in 1869, it became clear which requirements a rolling ball bearing should meet. However, these requirements have frequently changed over time. Initially, the bearing was intended to fix axles and shafts, to receive radial or axial loads, and to allow friction rotations for a mounted component, such as a wheel. 

In the early days of the bicycle, sliding friction was utilized, meaning that the wheel ran directly on the shaft, which resulted in high coefficients of friction, intense heat development, and wear. From that point forward, the principle of rolling friction became the main operating principle—the wheel moves through a ball bearing that consists of a fixed metal inner ring, a metal outer ring and lubricated metal balls that are evenly separated by a cage and located within the empty space of the housing.

If you look in engines, turbines, and other mechanical applications, metal ball bearings can be found throughout. However, the metal ball bearing is no longer the ultimate solution in today’s world, since ball bearings have to meet additional requirements for certain industrial applications. For example, lubricating ball bearings with messy grease is an enormous hygiene risk, which means that food packaging systems and medical technology manufacturers need to find alternatives that meet these requirements while bringing a technical advantage. With a "cost-down-and-technology-up promise", igus® continues to produce effective solutions that ensure excellent performance within the industry.

Technical advantages of xiros plastic ball bearings

Along with the fact that xiros plastic ball bearings are corrosion-free and heat-resistant, they can also be used within chemical environments. Also, since xiros® plastic ball bearings require no external lubrication, machine maintenance costs are reduced while the reliability increases. Ball bearings made from plastic materials are characterized by low-friction dry running, which minimizes the rolling resistance. The reason this occurs is because the metal balls do not have to overcome the resistance of the lubricant to start with a low breakaway torque.

Oliver Kreutz, Product Manager for xiros® plastic ball bearings, on metal ball bearings and plastic ball bearings:

“In order to guarantee almost comparable running properties, however, metal ball bearings require more attention from the user. Without time-consuming lubrication, which also causes material costs, the bearings will rust, subsequently deform due to the high frictional forces, and in the worst case cause a system failure. Engineers avoid these problems when they use plastic ball bearings. ”

Despite all of the incredible benefits that plastic ball bearings have to offer, they can also reach their limits. For example, speeds beyond 5,000 revolutions per minute can only be achieved briefly, since plastics deform faster than metals at higher speeds and heat. Metal bearings, on the other hand, are better equipped to handle higher speeds and higher loads. Here are the metallic version scores thanks to a combination of hardness and elasticity:

135 trillion test cycles within the in-house test laboratory

Yes, metal ball bearings may be at the forefront within these applications, but the evolution of ball bearing technology has allowed for a new mix of cards. What exactly does that mean? Igus® has always conducted rigorous research and testing within the igus® test laboratory, which executes almost 135 trillion test cycles per year. In addition to testing friction values ​​and wear rates, corrosion occurrence is also a huge priority. This has allowed us to produce and innovate the current ball bearing technology so that engineers and manufacturers can continue to create new applications and possibilities.

If you are interested in learning more about ball bearings, visit our xiros® ball bearing product overview. If you would like to speak to an expert about using xiros® plastic ball bearings within your application, please don't hesitate to contact Preston Souza, xiros® Product Specialist.

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