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Barden’s super precision ball bearings are suitable for use in electric surgical hand tools, as they provide high loads and operating speeds, high reliability and a longer tool life.

Barney Eley, product engineer at Barden, described a typical surgical application example: ’In surgical procedures, the operator of the sawing tool will have to put a relatively large load on the ball bearings.

’Since the tool may be used to saw through bone or cut through tendons, muscles, cartilage and other bodily tissues, the operating environment for the bearings is very harsh.

’Typically, the bearings are located close to the end of the cutting tool, often working inside the patient’s body and so resistance to acids and other corrosive media is critical.

’This means the manufacturer of the power tool will require a bearing that is compact enough to fit into the slender design of the tool and can cope with the high loads and relatively high operating speeds of up to 80,000rpm.

’In addition, the bearings will have to withstand the corrosive, slightly acidic operating environment inside the patient’s body.

’When you are designing bearings for surgical tools, there are many ways in which the bearing can be improved to suit the application.

’For example, we can alter the curvature of the raceways, as well as the height or size of the shoulders.

’Tighter curvatures within the raceways will lead to a reduction in contact pressure,’ he added.

Another important design consideration for the bearings is resistance to temperature.

As surgical tools require regular sterilisation in autoclaves, the bearings must withstand temperatures up to 140C.

’Most of our bearing designs for surgical cutting tools will be manufactured in corrosion-resistant 440C stainless steel, which provides sufficient resistance to cleaning chemicals and other aggressive acidic media,’ continued Eley.

’The bearings, which we supply as either deep groove or angular contact configurations, are normally provided with phenolic cages to provide further resistance to repeated sterilisation cycles,’ he said.

The harsh operating environment for the bearings also means that protection is required against any fine particles of soft tissue and bone that may penetrate the contact regions between the balls and the bearing raceways, which would then lead to high stress concentrations and could lead to the eventual failure of the bearing.

In order to counter these problems, Barden can provide integral shields that are designed to help retain the lubricant (normally a food-grade grease in surgical tool applications) while preventing the ingress of contaminants.

’This improved sealing design reduces the critical gap between the integral shield and the bearing inner ring to 60 per cent of that when compared with conventional shield and circlip designs.

’This means you get a reduction in operating noise, greater lubricant retention and improved protection from contaminants – all of which often leads to a longer life of the cutting tool,’ confirmed Eley.

In surgical applications, the cleanliness of the bearings is essential.

Barden’s manufacturing plant in Plymouth has more than 1700m2 of fully equipped cleanroom facilities, where all assembly, testing and packing operations take place.

’On a recent surgical sawing tool project, the bearings we provided were custom-engineered angular contact ball bearings with an outside diameter of 4.76mm and contained balls just 0.79mm in diameter, which is the smallest diameter we have provided for this sort of application.

’Here, our clean-room facilities were essential.

’Handling miniature ball bearings is not a simple task and we have the facilities and personnel here,’ he said.

The bearings provided were of a double-row cartridge design with a single inner ring and two outer rings.

’This design enabled us to incorporate an integral, one-piece shield on both sides of the bearing in order to prevent ingress of contaminants and to retain the lubricant.

’This one-piece, pre-loaded custom-designed bearing solution made assembly much easier for the customer, who simply had to “drop” the bearing into position within the overall tool-drive assembly,’ Eley concluded.

Barden

The Barden Corporation specialises in the design and manufacture of super precision ball bearings used in high performance applications across a broad range of market sectors. The company’s extensive product line includes key components for the aerospace and defence sectors, vacuum pumps, food processing, robotics and medical equipment.

The Barden Corporation specialises in the design and manufacture of super precision ball bearings used in high performance applications across a broad range of market sectors. The company’s extensive product line includes key components for the aerospace and defence sectors, vacuum pumps, food processing, robotics and medical equipment.

These products are predominantly radial, single and double row, angular contact or deep groove super precision ball bearings, which are offered in thousands of standard variations, although a significant proportion of production is devoted to special bearings. Bearings come in inch or metric dimensions with diameters ranging from 4mm (0.16″) outer diameter (OD) up to 180mm (approx 7″) OD and can operate comfortably at speeds of two million dN (bore in mm x RPM) or above. A variety of bearing seals, shields and metallic/non-metallic cage designs are available for all products.

Barden’s engineering team is able to offer unique solutions to bearing-related challenges by developing bearings and complex assemblies to assist customers in reducing parts count, assembly time and operating costs. Products across all ranges can meet and usually exceed ISO P2 (ABEC 9) standards whilst also offering full traceability back to raw materials where required.

The Barden Corporation is a key strategic member of the multinational Schaeffler Group, which specialises in bearing technologies and precision products for aerospace, industrial plant and automotive industries and has over 82,000 employees at approximately 170 locations in 50 countries. Schaeffler is headquartered in Germany and oversees three main brands: FAG, INA and LuK. Barden’s activities are supported by sister sites, The Barden Corporation (US) based in Danbury, USA, and the Winsted Precision Ball Company in Connecticut, USA.

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