Industrial Bearings

A bearing is a device that allows controlled relative motion between two parts. It is a component used to decrease the friction, which can be caused by any elements in motion, in order to reach its maximum efficiency, by eliminating the torque being converted into heat. So bearings help in decreasing the losses caused by conversion into heat, and increasing the efficiency of the machine or item.

Bearings can be broadly divided into two types depending on the purpose they are used for:  linear bearings and rotational bearings.

Linear Bearings: These bearings are used to obtain a smooth motion in a straight line. Drawers are a good example of this where the bearings help the drawer to be pulled out or pushed in a straight line, with relative ease.
Rotary Bearings: These facilitate an object to move around a central point. Wheel rotation on a shaft is a common example of the use of rotary bearings.

Bearings provide the following advantages in mechanical action:
1  Low Friction, especially the starting friction.
2  The ability to support both radial and thrust load, and high speeds of rotation.
3  Accurate performance under changing loads and speed.
4  High load carrying capacity.
5  Operating ability under extreme conditions of speed and performance.
6  Practically no wear in running.
7  Simple methods of lubrication.
8  Inherently precision mechanisms.

Uniformity in the manufacturing process is a crucial factor to ensure consistent performance by bearings. If variation occurs in the manufacturing process from part to part, they are tweaked to withstand a wider range of stresses, heat, etc.
This can in turn lead to variations in the performance of each bearing, either individually, or from lot to lot. The narrower the variation, the greater is the consistency of each bearing’s performance.

One of the most important things is selecting the correct bearing for a particular machine. The selection of ball and bearings for a given installation depends upon the following factors:
1  The load carrying capacity.
2  The speed of the shaft in rpm.
3  The type of service required from it.
4  The required life of the bearing.
5  The proportion of thrust to radial load.

Rotary bearings constructed out of ceramic are called ceramic bearings.  Ceramic hybrid bearings is the most common type of ceramic bearing, and have inner and outer rings made out of steel, but the balls made out of ceramic.  The most common types of ceramic bearings are angular contact and conrad.  Ceramic bearings are better than steel bearings in various ways. Ceramic bearings give increased stiffness, higher speed and acceleration capability, , higher accuracy, reduced lubrication requirements, lower friction and heat generation, low thermal expansion, and extended operation life. Bearings containing all ceramic balls are not advantageous and are generally not used, except in electric motor applications.

Pillow block bearings are a form of mounted bearing and are used to provide load support to a rotating shaft. The bearing housing is mounted on a surface parallel to the shaft axis. Elongated boltholes at the base of the unit allow for some adjustment and easy mounting of the pillow block bearing.

Industrial Abrasives

Abrasives are materials having a comparatively higher hardness and are used to shape other materials by grinding or abrasive action. These materials are used as loose grains, as grinding wheels, or as coated abrasives, coated on either cloth or paper (sandpaper being the most common example).

Abrasive products find a wide range of application in the industries including, but not limited to, grinding and polishing glass, cleaning and machining metals, cutting metals, glass, cement etc., grinding logs for paper pulp. Abrasives are also used to manufacture products like brake lining, non-slip flooring required in certain conditions, etc.

Abrasives are harder than the material that it is used to polish and this difference in hardness is what makes the abrasives work. Traditionally, various minerals were used as abrasives, typically those having hardness of 7 or more, on the Moh’s Scale of Hardness. Nowadays, many synthetic stones and other materials prepared artificially are used as abrasives in various applications. Diamond is a commonly used abrasive in various industrial applications, due to its high level of hardness. Various minerals that are used as abrasives are either crushed, or are already found in the powdered from, the grain size of which ranges from 1m to 2mm (1000micron=1mm).

Factors deciding how quickly a substance is abraded include:
Relative difference in hardness between two substances.
Grain size and its matrix- larger grains will cut faster as well as deeper.
The force at contact- more force will obviously mean more abrasion.
Type of lubricant or a coolant used.

Some of the naturally occurring abrasives are Calcite, Emery, Novaculite, Pumice, Rouge, and Sand. Some like Diamond and Zirconia Alumina are found in nature, but are also extensively manufactured synthetically. Other artificially prepared abrasives commonly used in industries are Borazon, Ceramic, Corundum, Dry Ice, Glass Powder, and Silicon Carbide.

While natural abrasives are often sold as dressed stones in the form of blocks, both naturally occurring as well as synthetic, abrasives are available in variety of shapes and sizes according to different use. These are usually bonded or coated abrasives, which includes blocks, belts, discs, wheels, sheets, rods, and loose grains. Grinding wheels are a type of abrasives that find a wide range of industrial applications, right from cutting, sharpening to shaping materials. Previously, such wheels used human power in the form of pedal or human operated cranks. However, now these comfortably work with the help of an electric motor. The high speed of motion imparted by such motors has necessitated the use of a coolant fuel for lowering of the resultant heat produced. However, many researchers suggest that such coolants or lubricants are more important to reduce the tensile stresses acting on the wheel.

The type of abrasive to be used for a particular work will be governed by the size, shape and the nature of the work piece, as well as the type of finishing desired.