Bearings play an important role in medical equipment

Precision bearings are among critical components in medical devices that are vital to ensuring patient safety. Yet, according to the 2022 Recall Index by Sedgewick, medical device recalls have reached a record number over the last three years, with safety issues being the top reason. Here, Chris Johnson, managing director at specialist bearing supplier SMB Bearings, explains why the correct choice of suitable ball and ring materials and the right product design can ensure high-precision bearings — and medical devices — have a long service life.

Precision bearings are used in a wide variety of medical devices including surgical power tools, ventilators, and heart pumps — and patient safety depends on them all. Whatever the device, there is an onus on medical device original equipment manufacturers (OEMs) to ensure that the right type of bearings are chosen, and fit precisely into the application. This responsibility is exacerbated by the fact that the development and approval of medical products is often a protracted and costly process.

What’s more, medical devices must pass regular checks and tests for long lifecycles. That includes standards like ISO 14971, which defines the best risk reduction practices throughout a medical device’s entire lifecycle — from design and manufacturing to distribution and maintenance.

Let’s examine more closely the demands on the bearings themselves. It’s vital that OEMs make the right choice of ball and ring materials.

Stainless steel versus ceramics
Traditionally, the ring materials of bearings in medical instruments have been made from high-purity metals such as martensitic stainless steel. For example, medical robots require high-precision components to undertake keyhole surgery and centrifuges must spin at high speeds to separate substances that have different weights. Applications that require high precision or high-speed capabilities are more suited to steel bearings. Martensitic stainless steel is ideal for surgical tools, for example, because of its ability to withstand the kinds of aggressive chemicals used in sterilization processes.