Some Bearing Developments Reviewed

Some Bearing Developments Reviewed All engineers, whether in production, design or process industries, should keep a watch on bearing developments, as their reliability can determine plant efficency, writes mike Page. Recent bearing developments include wider application of split bearings and bearings with higher precision and lower friction ratings. Some designs can take higher loads without any increase in size, while others have more compact housings to enable smaller mechanisms to be constructed, for example in handling and 'pick and place' systems. There is also a new range of machine tool ballscrew bearings.The selection of bearing developments has been taken from information sent to manufacturingtalk.com from Revolvo, Schaeffler, Danaher, Micromech and R A Rodriguez. * Revolvo roller bearings offer reduced downtime and longer life - Revolvo has expanded its range of split roller bearings with the introduction of flange, hanger and take-up bearing units.Totally split to the shaft, the bearings are designed to simplify and expedite installation. They can cut downtime to approximately 10% of that required to replace solid bearings of the same size.They also benefit from superior sealing arrangements, which, said Revolvo to manufacturingtalk.com, means longer bearing life with greatly reduced levels of maintenance.The flange, hanger and take-up bearing units are designed for use in the widest range of industries, providing reduced downtime and improved life in applications in quarrying, mining, steel, power generation, cement, water treatment and sugar processing as well as across main industries. Revolvo said that the bearings offer maximum strength and durability. The housings are manufactured from the toughest grey cast iron: a 250-grade material, to BSEN1561, 1997.The bearings are vailable in metric shaft sizes from 35mm to 300mm (and 13/16in to 12in). The SRB Flange units provide a simple and durable solution where bearings need to be mounted against horizontal or vertical faces.The flange units are produced with a spherical location to accommodate standard SRB bearing housings, and to provide easy alignment of shaft and equipment. * For screw conveyors - SRB hanger units support screw conveyor shafts.The unit comprises of a cast iron split housing into which standard SRB bearings are fitted.The provision of a drilled and tapped boss in one half of the housing allows for the unit to be mounted from the conveyor cross bracing, or any other suitable surface. The hanger units are protected by a double sealing arrangement, with many different sealing variants available, all of which can be customised.The hanger units are available in Metric shaft sizes from 35mm to 115mm, and Imperial sizes from 13/16in- 4.1/2in. SRB take-up units provide an efficient and readily accessible means of tensioning conveyors, elevators and large scale drive systems in materials handling applications. Available in both push and pull types, both of which are available with SRB's extensive sealing systems.The take-up units are designed for use on shaft sizes from 45mm to 160mm (111/16in to 6in). * Schaeffler X-life axial spherical roller offer more than double the life under the same loads - said by Schaeffler to be ideal for harsh operating environments, Schaeffler's X-life FAG E1 spherical roller thrust bearings have been improved with increased load ratings (static +10%, dynamic +35%), limiting speeds (+50%) and fatigue limiting load (+70%). Regarded by Scaheffler as a revolutionary achievement is the bearing's 170% increase in bearing rating life.The technical benefits of the bearing are numerous, as follows. * Operating life has more than doubled under the same loads. * Similar operating life under significantly higher loads. * Suitable for high speed applications due to lower friction levels. * Improved guidance and vibration characteristics due to very high running accuracy. * Less wear due to optimised lubricant film formation. * The lubricant is subjected to less strain due to lower bearing temperatures. These benefits result in higher machine availability, new design possibilities, more economical bearing supports due to downsizing; and lower operating costs due to reduced energy consumption. Schaeffler told manufacturingtalk.com that the most up-to-date kinematics technology and software was used to develop the new 294 and 293 series bearings, which are made from superior quality materials. The performance improvements were achieved by modifying and improving the bearing contact geometry and bearing kinematics.This included adding longer rollers with larger diameters, which results in higher load ratings.Surface improvements on the rolling elements also enable a lubrication film that is capable of supporting even higher loads. Improved osculation conditions and additional profiles further optimise the rolling contact.Modified osculation and precise rib geometry increase the load carrying capacity of the rib contact. A new sheet metal cage, with improved roller guidance and lubrication support, reduce wear and extend the life of the bearing.Higher axial load carrying capacity and lower bearing temperature as well as improved resistance to wear have enabled a further increase in operational reliability and economic efficiency. Moreover, the new FAG E1 spherical roller thrust bearings in X-life quality offer an even better price/performance ratio. In addition to these two X-life quality series, 292 series spherical roller thrust bearings are also available in E1 version, comprising longer rollers and larger roller diameters. Schaeffler's axial spherical roller bearings are ideal for applications in which very high axial loads are present and where shaft deflections or misalignments of bearing seats must be compensated for. The bearings operate reliably in the harshest of environments, including gearboxes, calendars, marine and rudder engines, lifting gear, construction machinery and steel rolling mills. * Metric Thomson super ball bushing bearings deliver higher performance - Thomson Super Ball Bushing bearings are now available in metric sizes 16, 20, 25, 30, 40 and 50mm. These precision bearings, available from Danaher, have a coefficient of friction as low as 0.001 enabling users to employ smaller and less expensive motors, belts, gears and ball screws when replacing high friction, plain bearings. Well suited for new applications, or as a drop-in replacement for existing applications, these new Thomson products are dimensionally interchangeable with competitive and legacy applications. Thomson Super Metric Ball Bushing bearings have a self-aligning capability of up to 0.5 deg that automatically compensates for inaccuracies in base flatness or carriage machining. Acceleration rates as high as 150m/s2 and steady state travel speeds up to 3m/s are delivered without the derating factors commonly required with linear guides.The bearings are available in adjustable, closed and open configurations. Double lip integral wipers keep contamination out and retain lubrication to maximise travel life.Lightweight, wear-resistant polymer retainers and outer sleeves reduce inertia and noise. General manager, Thomson North American linear bearings and Guides, Dennis Howe, told manufacturingtalk.com: 'When combined with our 60 Case shafting, Thomson Super Ball Bushing bearings can be configured to last 27x longer or carry 3x the load of conventional bearings, allowing users to reduce component size while saving space and cost'. He added: 'Thomson is the innovator of linear bearings and has supplied high quality products to the industry for more than 60 years. We believe that history of innovation and superior quality translates into better product reliability and performance, and users of our new metric Super Ball Bushing bearings will experience the difference'. * When height is critical, the FMB bearing solves precision rotary positioning problems - Micromech is offering the FMB bearing.The company claims that the FMB series is the ultimate in low profile, high precision rotary bearings ideal for positioning systems where both precision and height is critical. The various bearings sizes are only 8.5 to 12.5mm tall, yet deliver radial and axial run-out from 10 micron down to 1 micron and wobble from 6 down to 2 micronrads. Micromech told manufacturingtalk.com that the very thin and compact precision bearing is a turntable bearing designed to provide high performance circular motions in as small a package as possible.The bearings are currently available in nine standard sizes with ODs ranging from 120 to 350mm and IDs ranging from 40 to 250mm. Customised sizes are available up to 500mm OD to exactly match the application.They can support axial, radial and moment loading, have high rotary precision and repeatability, and provide significant cost savings up to 50% of classic turntable versions. * Classic turntables made simpler - classic turntables are designed by using a double pack of bearings which are often complex making them costly as they use more components and also assembly must be done by trained workers. The FMB design is much simpler with just one bearing having only one inner and one outer ring thus achieving significant cost savings.The bearings are made from high quality bearing steel 1.3505 with a through hardness of 60+/-2 HRc. If required by the application they can be manufactured in stainless steel No.1.4034 or similar.The super precision balls are made from bearing steel 1.3505 with a hardness between 62+/-2 HRc.These balls are spaced evenly in a PTFE filled plastic ball cage. The bearings are manufactured in two quality grades: normal and precision grade and are supplied by default with zero clearance.Micromech said that the bearings are very easy to install as most rotary bearings fit into a bore, which must be very precise to avoid deforming the bearing and spoiling the precision. The FMB includes a 0.5mm offset between the inner and outer races and counterbored holes to enable mounting directly onto flat surfaces. * FMB bearings improve accuracy - the Micromech FMB bearings is a single, four-point contact ball design, which consists of a single row of balls with a unique 'gothic arch' geometry raceway and PTFE filled plastic ball cage filled with super precision balls for low frictional torque. The special designed raceways are finished by precision grinding and the balls are selected within a tolerance of 0.1 micron.Through this optimized design the accuracy of these bearings are unmatched by others and friction is at an extremely very low rate. Having accuracy in a smaller, simpler package reduces design costs and envelope size, it makes installation fast and easy, and also gives ease of service, said Micromech. * Unitec bearings supplied for ballscrew drives - R A Rodriguez markets the Unitec brand of ballscrew support bearings for high performance machine tool applications. Now in addition to the high load and exceptional performance capabilities of this needle roller bearing range, the company has introduced a new range of ball bearings to meet more general high precision needs of ballscrews. The DRF/DRN double row ball bearings for screw drives are high precision components with a contact angle of 60 deg.They can absorb radial as well as axial forces from both directions and guarantee highest running accuracy due to their axial stiffness. The range is therefore ideal for lighter load applications that call for precise positioning and good repeatability.The integrated, low-friction seal prevents the ingress of dirt, enhancing reliability and operating life. The bearings are supplied ready-to-fit and lubricated.They may be specified with or without fixing holes and their design ensures swift and easy installation. Standard precision for the DRF/DRN range is the high accuracy p5/p6 precision class.For lower precision applications a commercial series of the DRF/DRN bearings is also available; this range carries the suffix NP.Eight types of bearing support units are also introduced in block or flange design.