The difference between these two types of bearings is based upon their design and manufacturing process, the application of these two different types of bearings is based upon the load and speed of the shaft. The ball-type bearings are commonly used where the speed of the shaft is high; however sleeve bearings are preferred for high load machines. This specific case is relevant to wind turbine, generally the load of the wind turbine is low, and however it has high speed therefore based upon generic technical evaluation the anti-friction bearings i.e. ball-type bearings are preferred. The ball-type bearings are lubricated through greasing or oil, the limited amount of oil or grease is required after specific period, which is actually positive aspect of using ball-type bearings. The sleeve bearings generally require forced supply of lubrication oil to prevent any damage to the bearing material; this requires entire circuit for the lubrication inclusive of pumps, heat exchangers and filters. The space economy is vital for wind turbine; therefore the ball-type bearings are preferred for such machinery design.
The raw material generally preferred for the manufacturing of the ball-type bearing is steel alloy. ...
The cages and seal cases are fabricated from "usually low alloy or plain carbon steels such as 1008 or 1015 steel" (Bruce, 1997). The bearing manufacturing begins with the forging of the steel bar into cups, cones, wear rings, and automotive rings; the forging process is hot forging and shall be helpful in the release of t he thermal and residual stresses from the material. The forging process is descriptive process; it includes the exposure of the steel bar in the induction heater system, the heating process shall be immediately stopped once the temperature reaches the melting point of the material; this temperature provided "maximum formability for hot forging". After the exposure towards high temperature, the hot bar is "sheared into slugs once it reaches the forging press; then the slug is upset, partially formed, and pierced" (Schmid, 2000).
Manufacturing of Inner and Outer Race
The manufacturing of the inner and outer race of the ball-type bearings has been summarised. The raw material i.e. forged rings of SAE-52100 Steel are introduced into turning operation, from where centre-less grinding is applied, the object is then heat treated, and hardness testing is verified. The process of rough grinding them commences, and ends with finish grinding. The object undergoes the honing and super finishing, followed by washing. The object is then coated with anti-rush agent before shipment (Bruce, 1997).
Normally more than seven parts are produced after every minute through this forging press. As per the recommended procedure, "the smaller forgings are rolled into larger rings in open die ring rolling where the part is worked between a