Comparing Bearings In Computers – Part 1
The demand for smaller and thinner computers and systems means that designers are having to create more compact products which are harder to keep cool. Heat is a nightmare for these types of products as they can reduce performance as well as reliability. If some parts become too hot, the memory can be wiped, destroying valuable documents, so it is vital that the heat is dissipated correctly.
The reliability of the heat reduction system (most usually a fan) is vital as the computer will be used for many years before being replaced. Two types of bearings are used inside a traditional computer fan and these are sleeve bearings, also know as plain bearings or bushings and ball bearings. These two vary in costs and reliability so it is important to know the difference between the two from an engineering point of view.
Life of the Bearings
It has been found that ball bearings will last half as long again as sleeve bearings when the temperature ranges from 25 degrees Celsius to 70 degrees Celsius. Not only will the ball bearing last longer, it will also be able to operate to temperatures that a sleeve bearing could not.
At 25 degrees Celsius, a typical sleeve bearing may last on average for 80,000 hours, with a ball bearing reaching around 95,000 hours. As the temperature rises, the percentage difference in life becomes staggering. The 18 per cent difference in the life span measured at 25°C pushes up to a staggering 80 per cent difference at the maximum operation temperature of a sleeve bearing (60 degrees), with the ball bearing lasting 54,000 hours and a sleeve bearing lasting 30,000 hours.
It is likely that in more expensive models, a designer or engineer would use ball bearings as they can operate for longer at higher temperatures, however they do cost more. If the equipment being designed is made for a short life, then it could well be that a sleeve bearing is used, or may be more suitable at lower heats for cost saving benefits.
Making the Bearings
Since the process of manufacture between ball bearings and sleeve bearings is quite different, the results are a difference in the precision of the final products. Powered and porous metals are used to create a sleeve bearing, resulting in certain deterioration under higher temperatures and even becoming unusable at around °C. Secondary machining processes can also become troublesome thanks to the hardness that can develop in sleeve bearings. If a designer needs absolute precision materials, then ball bearings are the only way forward, though sleeve bearings are a cheaper alternative should absolute precision not be required.