Bearing new developments in mind A

lthough steel is the traditional choice of material for bearings, there are

alternatives that are making an impact on the market. Take hybrid versions as an example, which offer a combination of steel rings and rolling elements manufactured from silicon nitride (ceramic). Designed to be dimensionally interchangeable with all-steel bearings in many cases, these help to increase reliability and robustness and provide excellent electrical insulation. Hybrid bearings also have a higher speed capability, are more resistant to potentially damaging abrasive particles and will, therefore, provide a longer service life than all-steel bearings in most applications. Versions have also been developed for use in electric motors which are more susceptible to damage caused by the passage of current. During the last three decades,

there has been an evolution in the advancement of highly engineered plastics in bearing applications. Polymer-based materials, such as teflon, phenolics and nylon, offer many benefits when used in less demanding environments where temperatures and stresses on the materials are less exacting, including part longevity, strength, corrosion resistance and reduced need for lubrication. Two other materials worth a mention are

Delrin, which is used in automotive, appliance and industrial applications where its low cost and water resistance makes it an attractive option; and Ultrahigh-molecular-weight Polyethylene (UHMWPE). These boast a

Sticking with what you know and using bearings you’re familiar with could mean missing out on valuable

new developments. Jane Curtis, bearings product manager at Brammer Buck & Hickman, looks at some of the most recent innovations in bearing technology

of polymer materials and thermoplastic resins to reduce maintenance requirements. In this approach, the lubrication entirely fills the bearing to coat all rolling elements and raceways with an even film. Holding up to four times as much oil as a traditional grease- filled bearing, the polymer material releases oil gradually around the moving parts to maintain the consistent coating. As the oil remains in position within the bearing, both particulate and fluid contaminants are kept out, while remaining resistant to chemicals which can damage seals and introduce foreign bodies. Such bearings are ideal for inaccessible or remote applications where re-lubricating and maintenance are difficult due to positioning.

smooth, low-friction surface and offer a great alternative to parts typically made from acetal, nylon or PTFE material.

LUBRICANT DEVELOPMENTS With 21% of bearing failures due to foreign matter ingress and 13% due to lubrication failures, developments in bearing friction, lubrication and wear have been a major focus for bearing manufacturers over recent years. Pre lubrication has seen some of the most important innovations, such as in the application


In such applications as stage technology, automation and control panels, slewing ring bearings need to carry out rotational movement in a confined space. So to meet demands, igus has launched the PRT-04 slewing rings which, in addition to being maintenance-free and wear-resistant, thanks to the use of high-performance polymers, are said to be 50% thinner and 60% lighter than standard PRT-01 bearings with a 100mm inner diameter.

The company’s sliding slewing ring bearings are suitable for the high cycle rates and loads

found in welding systems, indexing tables and the packaging industry, for example. The iglidur polymer slewing ring bearings (PRT) have sliding elements between the inner and outer bearing rings made of aluminium or stainless steel. Furthermore, the maintenance-free sliding elements, made of iglidur J plastic, ensure that friction and wear are minimised without the use of lubrication. This high-performance plastic withstands a maximum surface pressure of 35MPa. In addition, FDA and ESD-compliant materials are available. The new PRT-04 range is available directly from stock with inner diameters of 20 to 300mm.

igus 34 DECEMBER/JANUARY 2020 | DESIGN SOLUTIONS There are also innovations in lubricant

application for linear motion applications such as those used in medical equipment, measuring apparatus, palletisers and mechanical handling. Here, ball monorail systems are a particularly effective new solution which has been introduced. This is a linear recirculating bearing with integral lubricant reservoirs adjacent to raceways, which can vastly reduce maintenance for linear motion applications.

FURTHER INNOVATIONS For demanding applications – including highly contaminated environments – housed unit bearings are ideal. For challenging, heavy-duty applications, such as found in the aggregate, power generation and metal processing industries, bearings housed in solid steel are ideal. One such new bearing features an extended black oxide inner and a relief valve for non-purging seals. To reduce the risk of contamination as well as lowering lubrication consumption, this comes pre- assembled and pre-lubricated. Another recent innovation is roller bearings

with metallic shields to protect against external solid contaminants and deliver increased grease retention. Load capacity is increased by optimisation of the contact surfaces and the quality of the steel sheet metal cages which have been processed to increase their resistance and allow better contact with the rollers. This also allows increased operating speeds.

Brammer Buck & Hickman


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