Metal, plastic or ceramic ball bearings: when should I use which one?

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 are mainly used in most classic mechanical engineering applications. They are number one in terms of global sales volumes and are suitable for a wide range of different mechanical engineering applications. However, they always reach the limits of their application when other requirements are placed on the bearing in addition to load capacity and speed. This applies, for example, to various sectors such as the food industry or medical technology. Specifications such as suitability for contact with food or suitability for use in cleanrooms are decisive here. For this purpose, system manufacturers often require food certification in accordance with EU standard 10/2011 or the FDA (American authority: Food and Drug Administration).

Plastic and its advantages

The advantage of plastics lies in the variety of materials. Thus, it is possible to choose different base polymers for the most diverse applications, which are precisely suitable for the application in terms of their specifications. In recent years, basic polymers such as POM, PP, PEEK and other plastics have become established. Plastic ball bearings can be suitable for the following industries and applications:
 

• 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)

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.