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Which Material Should I Choose for Ball Bearings: Metal, Plastic, or Ceramic

Choosing the right material for ball bearings is not always easy. In this article, you will find a brief summary of whether and when ball bearings made of metal, plastic or ceramic are suitable.

Limits of metal ball bearings

Metal ball bearings hold the top spot in global sales for their extensive use across various mechanical engineering applications. Renowned for their versatility, they cater to a broad spectrum of engineering needs due to their high load capacity and speed adaptability. Yet, their utility has boundaries, especially when additional specifications are demanded. Industries like food processing and medical technology impose stringent requirements beyond mere mechanical performance. Factors such as compliance with food safety standards and cleanroom compatibility become critical. Consequently, system manufacturers in these sectors often mandate certifications like the EU standard 10/2011 or approval from the FDA (American authority: Food and Drug Administration), ensuring the bearings meet the rigorous health and safety regulations necessary for their specialized applications.

Plastic and its advantages

Plastics offer a significant advantage due to their diverse material options. This diversity allows for the selection of specific base polymers tailored to meet the exact requirements of various applications. Over recent years, fundamental polymers like POM, PP, and PEEK, among others, have gained prominence in the industry. As a result, plastic ball bearings have proven to be appropriate for a wide range of industries and applications, thanks to their adaptability and the precise properties of the plastics used.

Food industry (advantage food contact)
Medical technology (advantage FDA-compliance)
Chemical industry (advantage chemical resistance)
Textile industry (no adhesion of dirt and dust)
Vacuum/High temperatures (no destruction of the lubricant)
Special applications such as MRI or metal detectors (metal-free advantage)

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In addition to the fact that xiros plastic ball bearings are corrosion-free and heat-resistant, they can also be used in chemical environments. Maintenance costs for systems and machines can be reduced and reliability increased. The plastic ball bearings are characterised by low-friction dry operation, which means that xiros ball bearings do not require lubrication. This allows the rolling resistance to be reduced to a minimum. The reason: the balls do not have to overcome the resistance of the lubricant so that they can start with a low breakaway torque. Marcus Semsroth, Product Manager for xiros ball bearings, speaks on metal and plastic ball bearings:

"In order to guarantee almost comparable running performance, metal ball bearings require more attention from the user. Without time-consuming lubrication, which also incurs material costs, the bearings rust, become deformed due to the high frictional forces and, in the worst case, cause system failure. Engineers avoid these problems when they use plastic ball bearings."
But polymer ball bearings can also reach their limits. For example, speeds beyond 5,000 revolutions per minute can only be achieved in the short term, as polymers deform more quickly than metals at higher speeds and the resulting heat generation. Bearings made of metal, on the other hand, have the edge when it comes to higher speeds and the absorption of higher loads. Here, the metallic version scores due to a combination of hardness and flexibility.

135 trillion test movements in the in-house test laboratory

Yes, metal ball bearings are ahead in these disciplines, but the evolution of ball bearing technology allows a new shuffling of the cards. What exactly does this mean? igus has always conducted basic research and has a test laboratory with around 135 trillion test cycles per year. In addition to investigations of coefficient of friction and wear rates, corrosion behaviour is also on the agenda.

Ceramic bearings for extremely high temperatures

In the realm of materials engineering, plastics and ceramics can be optimized for reduced friction through the use of aqueous lubricants and careful structural design. This can result in impressively low coefficients of friction, often below 0.1, which contributes to minimal wear and a significantly extended service life. However, when considering load-bearing capacity and potential speeds, plastics and ceramics fall short of metals. Metals boast a superior blend of hardness and flexibility, accommodating a wide range of applications. Plastics, while softer and more prone to deformation under high temperatures, offer versatility. Ceramics, despite their remarkable hardness, suffer from low flexibility and are susceptible to breakage under sudden impacts. Moreover, the thermal conductivity of ceramics and plastics is inferior to that of metals, which further constrains their operational speed limits. Understanding these material characteristics is crucial for selecting the appropriate material for specific engineering applications.