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.

Linear Bearings

When an object is required to be moved in a straight line along a straight line, linear bearings are used to achieve this motion with relative ease. This is especially required to be done with high precision in a manufacturing unit or an industrial setting. Here, the requirement is usually such that the machine or the equipment needs to be transferred in one direction only, with a to and fro motion, and back to its original position. Usually this is a repetitive motion, and it requires an ease of doing this quickly, and due to the uni-direction motion, the function of these bearings are very simple. The function of the bearing would be to provide a sliding or a rolling contact between the machine or equipment, and the races on which it has to be moved and provide an easy motion among the parts. Applications involving shorter length of travel and higher accuracy with some amount of noise and vibration find high use of linear bearings.

A linear bearing provides a sliding motion using balls, slides, bushes, rails, and lubricant. Linear bearings come in various sizes and strengths suited to different requirements of the industry.

Large automated systems such as positioning tables and robotic assembly lines finds a high use of various types of linear bearings. Linear ball slides are one such type, which are very compact, and have a short stroke and a small form factor. Such type of linear bearings can stroke up to one-third of the slide length. If the requirement is for a higher load capacity, crossed roller bearings would be suited in such situation as it can take more loads due to the presence of a contact line between every roller and the raceway.

For general uses of linear bearings, such as workstations and drawer glides, a plastic or low grade metal is usually used, as the stress requirement of the bearing is really low. Linear guide is the term used for linear bearings that have similar requirements in an industrial set-up such as motion control system. Different types of linear bearings are required in various general uses such as precision dispensing, optic alignment, vision inspection, disk certification, automated production equipments, water testing and handling, precision gauging, etc.

There are certain types of linear bearings that can also rotate along with sliding. These are especially useful shafts that move axially as well as rotate. Such special requirements are found in certain industries like printing industry, textile industry, leather processing units etc. These are special type of linear bearings and not generally employed when only linear motion is required.

The main advantage with linear bearings is the relative ease with which it can be installed, and at a low cost. But standardization of products is rarely found due to the presence of number of manufacturers. For this reason, special care needs to be taken regarding the bearings, length, width, diameter, and also the load capacity required for specific application and condition here it is going to be used. Materials such as plastic, bronze or stainless steel are usually used for manufacturing linear bearings. A linear bearing maybe self-lubricating and cleaning, still some bearings may require regular cleaning and lubrication to increase the longevity of such bearings.

Ceramic Ball Bearing

A ceramic ball bearing is a rotating support, just like a steel ball bearing, which is placed between moving parts in order to allow them to move easily. Ball bearings usually contain small metal balls. Ball bearings are commonly used for industrial and commercial purposes. Ball bearings are essential for the smooth movement of parts or whole pieces, and in absence of these components, various parts would have to be replaced constantly, because of the wearing caused by friction.

Ball bearings will usually consist of inner and outer rings, inner and outer raceways, balls and a ball cage. The balls follow the inner and outer raceways. The surface of the inner ring is where the inner raceway is located, and the surface of the outer ring is where the outer raceway is located. The raceways make available a smooth track and unhindered movement for the balls.

The mass of the ceramic balls is about 60% less than that of steel balls. When working at high rpm, the centrifugal motion significantly affects steel balls, as they are pushed to the outer race. The shape deforms from “round” to “egg shaped,” which leads to wear and the bearing will eventually fail. As ceramic ball bearings offer 50 percent greater rigidity and 50 percent less mass, a 30 percent increase in speed will have no significant effect on the life of the bearing.

Ceramic ball bearings have less vibration levels and lower operating temperatures as compared to steel balls. This is due to the nearly perfect roundness of ceramic balls, and greater smoothness, as a result of which friction is reduced by 70 percent. The hybrid ceramic ball bearings have higher rigidity and higher harmonic frequencies result in low vibrations. Ceramic balls do not react with steel raceways like steel casters. “Cold welding,” results from the steel-ball to steel-raceway interaction, which causes surface roughness, excessive heat and finally, bearing failure from wear. The ceramic balls in a hybrid ceramic ball bearings have no such reaction with the steel raceways, which can assure longer bearing life. Added advantage is that the equipment or machine can be used at the same speed with grease as a lubricant instead of oil. Whenever grease is used as lubricant with steel ball bearings, it is required to reduce the speed to attain the same bearing life compared to oil lubricant.

Among the newer generations of bearings, hybrids ceramic ball bearings offer distinct advantages over all-steel counterparts. These types of bearings mix bearing-grade silicon nitride (ceramic) rolling elements with steel rings that exhibit significant advantages compared to older all-steel bearings.

Ceramic ball bearings can be used at higher speeds and lower operating temperatures; are lighter, harder, and more durable and prove highly resistant to wear. The relatively increased hardness results in improved wear resistance against hard particles, and vibration, and their highly rigid nature increases the bearing strength and reduce the deflection under the load, and hence results in reliable performance.

Hybrid bearings have natural insulating properties, which are particularly beneficial in applications that involve variable speeds in motors and generators, where problems due to electric arcing may arise, and resulting bearing damage may take place from the occasional shaft currents. Hybrid bearings are a feasible alternative for insulating from the inside.