Most people don’t give much thought to bearings. Without bearings, most of our modern machinery wouldn’t work. Or at least wouldn’t work as efficiently. These precision-made components enable machines to move at extremely high speeds while carrying very high loads. There are many different types of bearings but they all have one thing in common: contaminants can cause bearings to fail.
Contamination from foreign particles can get into the spindle bearings in a number of ways. Coolants can introduce foreign particles into the spindle as can vigorous cleaning with air or water hoses. To keep bearings moving freely, contaminants must be kept out of the spindles.
So, how can you keep the bearings contamination-free? The most effective way is with effective sealing. There are a few different types of bearing seals and we will discuss them.
A labyrinth seal consists of a series of interlocking channels that collect contaminants under high velocity and expel them. These seals do prove effective while a bearing is in rotation but it isn’t effective when the spindle is not moving. A labyrinth seal can also become overwhelmed by high volumes of coolant. Contact seals when used with labyrinth seals also add to the protection of the lubricants. Made from either rubber or metal, contact shields have a tendency to wear from seal friction and are limited to certain applications.
Instead of using just a mechanical type seal, a change to an alternative sealing solution is another option. Although these methods require a higher initial cost, they may be worth the money to extend or save spindle life.
In air-purge sealing a contact type seal or shield is used in combination with a labyrinth seal and uses low pressure air flow to expel coolant and debris out through a port. This air-purge system should also be used during cleaning.
The AirShields™ or air-seals system combines a labyrinth seal, a floating seal, and the air-purge system. In this system it is the floating seal that helps reduce friction when the spindle is moving and when the spindle is stopped it forms a barrier against contaminants.
We have just touched on the available sealing options but it is important to find the right sealing solution in each application to prevent bearings from being damaged by contamination. Taking steps to improve sealing will lead to more efficient and productive machinery.