Chris Johnson, Managing Director of Specialist bearing supplier SMB Bearings, explains why the right choice of the right ball and ring materials and the right product design can ensure that high precision bearings and medical devices have a long service life.
Precision bearings are among the critical components of medical devices that are vital to ensuring patient safety. However, according to Sedgewick’s 2022 Recall Index, medical device recalls have reached record numbers over the past three years, with safety concerns the main reason.
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. Regardless of the device, original equipment manufacturers (OEMs) of medical devices have a responsibility to ensure that the right type of bearings are chosen and accurately matched to the application. This responsibility is compounded by the fact that the development and approval of medical products is often a long and expensive process.
In addition, medical devices must pass regular checks and tests for a long life cycle. This includes standards such as ISO 14971, which defines best practices for risk reduction throughout the life cycle of a medical device, from design and manufacturing to distribution and maintenance.
Let’s take a closer look at the demands on the bearings themselves. It is vital that OEMs make the right choice of ball and ring materials.
Stainless steel versus ceramic
Traditionally, bearing ring materials for medical instruments have been made from high-purity metals such as martensitic stainless steel. For example, medical robots require high-precision components to perform hole 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 best suited for steel bearings. Martensitic stainless steel is ideal for surgical tools, for example, because of its ability to withstand the types of aggressive chemicals used in sterilization processes.
However, in harsh environments, steel bearings can be susceptible to corrosion, so heavy-duty ceramic bearings are ultimately a better choice to extend the life of the device. In these cases, ceramic bearings are preferred.
Equipment applications best suited to ceramic materials include magnetic resonance imaging (MRI) scanners. Hospitals want to ensure that their high-value machines run efficiently, without the need for high-maintenance parts. Because MRI scanners use a strong magnetic field to generate two-dimensional or three-dimensional images of any living subject, standard steel bearings cannot be used due to their magnetic properties. Instead, the application requires non-magnetic or non-conductive components, in this case, quality ceramic bearings.
Full ceramic bearings are harder than steel, with superior corrosion and heat resistance, higher dimensional stability and lower density. They are significantly more expensive than their steel counterparts, but in general, ceramic bearings are worth the extra investment to help ensure that high-value applications, such as laboratory equipment, perform efficiently and with longevity. In fact, using the wrong components in such equipment can cause contamination or stop working altogether.
Regarding the choice of ball material with the bearings, plastic ball bearings are a good choice for MRI scanner beds, or indeed any lower precision application in medical environments where there is no magnetic distortion. Plastic ball bearings are also completely non-magnetic when fitted with polymer, glass or ceramic balls. Rings can also be made from different plastics, such as polyether ether ketone (PEEK) or polytetrafluoroethylene (PTFE). Each has excellent chemical resistance properties. PEEK materials in particular have improved corrosion and abrasion resistance, strength and toughness, X-ray radiolucency and excellent sterilization performance.
Smaller bearings possible
Apart from the materials, the design of the high-precision bearing should also be considered. In general, medical device manufacturers have to develop their products to work well in a limited space. This equipment requires the smallest possible pads to fit, especially for handheld devices. For these applications, SMB Bearings recommends miniature stainless steel bearings, defined as having an inside diameter of less than 10 millimeters. However, the smallest bearing in SMB Bearings’ miniature range is designed to fit a shaft just 0.6 millimeters in diameter, about the size of a pin head.
For rotating hand-held medical equipment, such as dental drills, the bearings may need to operate at high speeds. A bearing with a 0.6 millimeter bore can deliver 160,000 revolutions per minute (rpm), giving an impressive rotational speed capability, while some larger bearings can increase their speed by using ball retainers , made with materials such as Torlon or reinforced. polyamide
If rotational accuracy is important to the application, which is typically the case with medical instruments, manufacturers should consider choosing a precision brand bearing. There are many low-cost bearings on the market, but their inconsistent accuracy and quality make them dangerously unsuitable for high-precision applications.
Good lubrication
Next, we look at the lubrication requirements of bearings in medical applications. Ceramic bearings do not require a lubricant to operate, while steel alternatives may require routine maintenance to relubricate the part. In these cases, good lubrication is also vital for bearing performance in medical applications and to ensure patient safety. For example, for bearing systems that rely on grease lubrication, it is recommended that the lubrication be biocompatible, so that there is no risk to the patient’s health even if the equipment comes into contact with the skin or the tissues
In fact, lubricants rated H1 or H2 by the National Sanitation Foundation (NSF) are usually recommended for medical devices. H1 lubricants are tasteless, odorless and classified as safe for human consumption. They are used in machinery such as pumps, conveyors and mixers, and even food preparation environments where contact with food is technically unavoidable. H2 lubricants are recommended for devices that do not come into direct contact with food, beverages or pharmaceuticals.
Medical device manufacturers should also consider biocompatible lubricants that meet ISO 10993, a series of standards for evaluating the biocompatibility of medical devices to manage biological risk.
The above examples show that precision bearings in medical devices are critical to ensuring patient safety. However, with the support of an expert specialist bearing supplier, OEMs need not feel the burden of stipulations such as ISO 14971. Instead, they can choose the right bearing material and design to ensure medical devices remain operational and pass inspections, and most importantly, help safeguard patient safety in the future without the need for recalls.
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As technology becomes increasingly present in all aspects of life, healthcare providers have been looking for ways to use these advances to better the lives of their patients. One such example is the use of bearings to improve patient safety in medical devices. Ikaroa, a full stack tech company, has developed a cutting-edge bearing system that is designed to replace traditional, discrete parts in medical device designs, improving patient safety and ensuring accurate performance.
The unique, patent-pending design of Ikaroa’s bearing system simplifies the construction of medical devices, requiring fewer components and providing greater accuracy and security when used in a variety of applications. This accuracy ensures that medical devices operate safely and consistently for the duration of their intended operation.
Ikaroa’s bearing system also reduces the mechanical complexity of a medical device, making it easier to install, maintain, and repair, while providing an enhanced level of protection. This can result in significant cost savings to the provider while providing greater safety and accuracy to the patient.
By eliminating traditional, discrete parts inside medical devices and replacing them with Ikaroa’s bearing system, the medical device industry is able to create more reliable and secure designs, while improving overall patient safety. This improved security and accuracy can also increase the value of medical devices, as well as provide longer life spans.
Ikaroa’s innovative bearing system can be used in a variety of medical devices to provide enhanced patient safety and improved accuracy. By taking advantage of the existing resources and technologies available today, Ikaroa has revolutionized the medical device industry and is paving the way for improved patient safety in the years to come.
