Ball bearings and sleeve bearings are used extensively in DC fan manufacturing to provide effective cooling solutions. Both have advantages and disadvantages all of which should be considered in the design application phase.
Comparative Characteristics of Ball Bearing and Sleeve Bearings
Most ball bearing fans operate for approximately 50,000 hours or more. A conventional sleeve fan will operate for more than 30,000 hours. There are a variety of factors that determine the overall life of a fan such as ambient temperature, fan mounting position, amount of friction, and bearing lubrication used.
Under some conditions ball bearing fans and sleeve bearing fans have comparable life spans. However, when ambient temperatures or friction increase, or when mounted in a non-vertical position, the life of sleeve bearing fans decreases significantly. Sleeve bearings have broad line-contact between the shaft and bearing during the back-and-forth sliding motion which generates more friction than the point contact of ball bearings.
To reduce friction and minimize overheating, fans need lubrication. For ball bearing fan systems thicker lubricants are needed. These include lubricants with more additives that are subject to less evaporation. The lubricants within sleeve bearing fans have a greater concentration of oil, and the sleeve bearings' bushings can only hold a fixed amount of lubricant. Since there is no periodic recharging of the oil, the lubrication within a sleeve bearing system is more likely to evaporate.
Sleeve bearing fans generally run quieter than ball bearing fans at low fan speeds. Their noise level depends on the clearance of the fan's bushing and variances in component parts.
Sleeve bearings are not precision made, and are therefore less costly. Conversely, ball bearing manufacturing is a more extensive process which results in a higher cost.
PTI’s Sealed Bearing System: The high performance/low cost bearing solution
Recent improvements in sleeve bearing manufacturing have not resolved the problem of oil leakage and dust contamination that occurs in the impeller side opening of the bearing. Pelonis Technologies' new “Sealed Bearing System” solves this problem by using a special sealer in the impeller side. Because the oil remains in the bearing without dust contamination, the sleeve life fan compares favorably to the life of the ball bearing fan, generating less noise and providing a shock resistant operation.
Pelonis D-Series Fans features an energy efficient DIFFERENTIAL 4-switch circuit design that reduces voltage spikes and provides smooth and efficient operation.
The D, R, P, and K Series Fans feature Pulse Width Modulation (PWM) and extra fan features for maximum performance and efficiency.
The Pelonis “Sealed Bearing System” is a practical solution for DC fan applications that require the benefits of both sleeve and ball bearings. The cost of the SBS technology is slightly higher than the conventional sleeve bearing technology but well below the ball technology. In addition, SBS reduces oil leakage and dust contamination associated with sleeve bearings, thus making SBS an ideal high performance/low cost environmental DC fan bearing solution.