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Hybrid Bearing Applications

Machine Tool Spindle Bearings

When speed is paramount hybrid ceramics hold the key to solving the bearing problem. Hybrid machine tool spindle bearings have proved popular throughout the industry. Due to the reduction in density of silicon nitride rolling elements in comparison to the traditional steel equivalent, silicon nitride rolling elements experience a reduction in centripetal force which acts upon them at high speeds found in a machine tool spindle application. This reduction in centripetal force means the rolling elements suffer less slipping and in turn a reduction in wear.

These properties result in two key benefits of hybrid ceramic bearings over traditional bearings, a 30%-50% increase in speed and an increase in the fatigue life of the bearings. The direct benefit to the end user is that fewer breakages means less machine down-time increasing output abilities and fewer replacements.

Electric Motor Bearings

Hybrid bearings have proved to be exceeding popular in the electric motor applications in particular the emerging wind energy market has seen major benefit in the use of hybrid bearings. Issues arise in electric motor bearings when an electrical current is passed through the bearing causing electrical pitting. The current will cause micro-welds to occur between the race and ball leading to dramatic increase in wear, noise and lubricant aging. Once this has occurred the bearing has to be replaced.

Due to the insulating properties of the ceramic materials, hybrid bearings do not allow the current to be passed between the races overcoming all the electrical pitting issues found with traditional steel bearings, this coupled with the additional benefits such as longer life and higher speed capacity of hybrid bearings means that electrical motors have been revolutionised.

Turbo Charger Bearings

turbo-charger

Manufacturers of Turbo Chargers have always aspired to replace bushes for ball bearings. This reduces turbo lag and increases performance significantly.

Unasis has successfully assisted our customer by designing a custom pair of hybrid ball bearings to enable them to achieve turbo speeds in excess of 220000 rpm whilst boosting pressures of up to 4 Bar.

The shaft temperature sees 300°C while the housing sits at around 200°C. Contact your Unasis representative to discuss your cryogenic application.

Cryogenic and Cryogenic Pump Bearings

Ceramic-Bearings078

At the extreme temperatures, cryogenic applications demand the most out of all their components including bearings. At -196oC liquid nitrogen will freeze water in the air blowing past, at these temperatures if a standard bearing were to be used all the clearance would be pinched out of it rendering the bearing unable to rotate.

Due to the significantly lower thermal expansion coefficient of ceramic materials, ceramics will not contract as significantly as their steel counterparts and as such will work under the coldest cryogenic temperatures. In addition, ceramic bearings are able to withstand the thermal shock of being flooded with cryogenic fluid and the considerable instantaneous temperature drop that this results in, the high stresses this places on materials would cause 52100 steel bearings to fail.

pump

Unasis cryogenic pump bearings have been used to great success in a submerged pump. The pump works in a vertical orientation immersed in a cryogenic liquid such as liquid Argon or Nitrogen at operating temperature of between -155° to -196°C. An angular contact bearing pair was designed with Stainless Steel Races, Silicon Nitride Ceramic Balls and a custom PEEK Cage. The Unasis XTR dry film lubrication was also applied to meet with the demand of Extreme Low Temperature as well as extremely high loading and speed conditions.

Actuation Bearings

Microtechnica-bearing

The very stringent requirements of light high accuracy light weight meant that a completely custom bearing had to be designed for an airborne actuation device.

The accuracy requirement meant that Abec 7 precision race tolerances were required while limited space meant that a double row angular contact design with castellated faces was designed to interact with the mating components.

To further reduce weight the outer diameter of the bearing was manufactured in a concave form. The inner ring and cage is split to enable the bearing to operate independently on each axis of the bearing to rotate in opposing directions simultaneously.

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