A ball bearing is a circular joint that connects a rotating part to another, usually stationary, part of a machine. It allows the rotating part to provide or receive structural support while significantly reducing the amount of friction caused by the rotation. Figure 1 shows an example of a self-aligning ball bearing.
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The most common ball bearing application consists of a rotating shaft that needs support. The shaft fits snugly inside the inner circle, called a race. When pressure is exerted perpendicularly to the length of the shaft, such as the weight of a car pressing down on the car's central axle, the bearing provides support for this weight making it a radial bearing. If the pressure is exerted through the length of the shaft the bearing is an axial bearing.
Ball bearings consist of two grooved, circular tracks carved into short, hollow cylinders, called raceways, which sandwich a set of balls, also referred to as the ball bearing rollers. As the inner race rotates, the balls between it and the outer race begin to roll, significantly reducing the friction between them.
These balls are sometimes spaced out from each other by a retainer, also called a cage, which is a series of circular harnesses that go around each ball and connect rigidly to the harness of the next ball, maintaining a fixed distance between them as they roll.
Because the smoothness of the tracks and the balls and their ability to roll freely is what allows the rotation to occur without much friction, debris mustn't be allowed onto the grooved track, where they could stop a ball from rolling or cause scratches or dents, causing the bearing to fail. For this reason, most ball bearings are built with seals or shields that close off the grooved space between the races from the rest of the machine environment. Figure 3 shows various shielded, sealed, and open bearings.
Regardless of whether the bearing is sealed or open, it is typical for ball bearing lubricants, such as grease or oil, to be distributed across the balls and tracks to ensure that the balls rotate freely and allow a temporarily stuck ball to slide smoothly against the grooves.
The outer surfaces of the races may have additional structures, such as screw holes that allow them to attach to other parts of the machine. However, most bearings are secured by C-shaped rings, called snap rings, or are sized so precisely that they fit snugly into their housing and clench tightly to the shaft without the need for additional support.
Ball bearings are named according to features of their physical design. By understanding their designs, one can appreciate the logical relationship between the design, the name, and the load-bearing capacity of each of the following types of ball bearings.
Deep groove ball bearings have grooves cut more deeply than some alternatives. As a result, the walls of these grooves surround more of each ball.
Because the balls are more fully surrounded, they have more wall-surface against which they can roll and transfer loads in more directions. For example, the pressure exerted through the length of the shaft from the left will be transferred to the left walls of the inner race, which will press on the balls, which will push against the right borders of the outer race, which will finally press against some rigid part of the larger machine. For this reason, a deep groove ball bearing is suitable for bearing axial loads from both the left and right directions, in addition to radial loads. Frequently, they carry both types simultaneously, in which case, we say they are operating as radial-axial bearings.
Angular contact ball bearings feature asymmetrical grooves caused by one groove wall being longer than the other. Which division is more extended depends on the other race, with the critical thing being that the longer walls of each race oppose each other. For example, if the left wall of the outer race comes down farther, then the right wall of the inner race should come farther up, and vice versa, such as in Figure 4.
This allows the bearings to support axial pressure from the length of the shaft in the direction of long-wall opposition. Of course, the inner and outer races still cup the balls from the top and bottom, thereby ensuring that radial pressure is supported. As a result, angular contact ball bearings achieve a radial-axial load-bearing ability similar to deep groove ball bearings, but only in the direction of long-wall opposition.
When the bearings must support axial loads in both directions, a second angular contact bearing is sometimes flipped the other way and installed adjacent to the first one. This allows one bearing to provide long-wall opposition in two directions. However, this arrangement takes up the additional axle and clearance space. A double-row angular contact bearing is often preferred.
A double-row angular contact bearing consists of two rows of balls, separated by a long, inner wall that protrudes from the outer race. Each row of balls is held in place on the other side by a long wall extending from the inner race. Axial pressure from the shaft is exerted, through the balls, to the long inner wall of the outer race, attached to some larger structure of the machine.
As you can see in Figure 5, this design is effectively a system of two single-row angular contact bearings that have been structurally unified and consolidated.
Unlike the previously discussed types, which all have inner and outer races, thrust ball bearings have left and right races, whose grooves sandwich the balls from the left and right directions. This makes them better than the others at supporting axial loads because the centers of the tracks, rather than just extra-long walls, hold the balls from those directions, as seen in Figure 6.
However, because the grooves do not extend to surround a significant enough portion of the tops and bottoms of the balls, heavy radial loads are not supportable, and these bearings are liable to collapse if such a force is exerted.
A single-row thrust bearing has just one row of balls and is suitable for applications where axial loads occur in just one direction.
To support rotation, only one of the races attaches to the shaft, while the other has a larger bore diameter, allowing the shaft to pass through it with clearance. When the shaft rotates, the race to which it is attached also rotates, causing the balls to roll between it and the other race, fixed in place on the machine.
When the shaft is attached to the left race, axial pressure is exerted through the shaft and is supported by the balls and race to its right. But, if axial pressure is exerted from right to left, the left race will have no support from the bearing structure and will simply be pushed away from the rest of the bearing, which may break apart.
Double-row thrust bearings consist of two rows of balls sandwiched between three races. In this design, the middle race attaches to the shaft, which passes with clearance through the larger bores of the outer races. As a result, axial pressure exerted in either direction is supported by the row of balls and outer race on the opposite side.
The surface of the race that encounters the housing may be flat or spherical. When the surface is flat, it must lie flush against the housing, leaving no room for misalignment between the shaft, the bearing, and the housing. However, when the surface is spherical, it rests in the housing like a ball in a socket, making the shaft slightly misaligned relative to the housing during installation and operation.
Self-aligning ball bearings frequently feature two rows of balls instead of just one, which provides two rows of contact points against the grooves of the races. One of the races holds those rows separately through a dual groove, while the other has one extra-wide track that spans both rows, as shown in Figure 7.
If the angle between the length of shaft and the plane of the bearing shifts slightly away from a perfect right angle, one of the rows of balls will still line up with the center of the groove of the outer race. The alignment provides continuous and robust radial support until the shaft shifts back to its proper right angle.
Bearings with this design are often used when installation conditions make it challenging to achieve a perfect right angle between the shaft and the bearings in the first place. The self-aligning design will successfully support the radial loads with a near-right angle.
Y-bearings are ball bearings with an extra-long inner race that extends like a short pipe out of both sides of the bearing. These extensions provide two screw holes to fasten set screws into corresponding screw holes on the shaft. If two sticks were poked through the bearing's screw holes until they touched, they would form a 120-degree angle and might be said to resemble the top of a "Y," which is why these bearings are called Y-bearings. This screw-hole design allows these bearings to be installed on shafts already in place. While this attachment method is convenient, its axial load-bearing capacity is limited.
Thin section bearings have particularly thin races, having narrower grooves and accommodating smaller ball sizes. The decreased width and ball size require less material, which reduces the overall weight and size of the bearings, which can result in lower operating costs. However, the smaller ball size makes for less contact area, so the overall load-bearing capacity is limited. Accordingly, thin section bearings are most suitable for precision instruments, where space is limited, and radial loads are not very heavy, such as medical equipment or astronomical machinery.
When a ball bearing has reached the service life predicted by the work hours formula or shows signs of material degradation, owners should inspect it. Some symptoms of bad ball bearings can be excessive noise or heat. If it is an open bearing, this is accomplished by first assessing the condition of the lubricant, then removing the balls from the races and cleaning the surfaces thoroughly. Finally, owners should carefully wash the surfaces and inspect them for wear or abnormalities. If it is a permanently shielded or sealed ball bearing, users should supply an initial torque and observe the bearing during free rotation. Depending on the outcome of the appropriate inspection, owners should replace the bearing.
Because a ball bearing is a structural joint, its removal often requires temporary support that will hold the parts of the machine that the ball bearing joins. For example, the wheel bearings of a car securely join the central axle to the wheels, holding the car's weight up off the driving surface. First, it is necessary to support the vehicle with a jack or similar support to replace wheel bearings.
Frequently, a secure housing encases the bearing and is attached to the larger machine. Therefore, removing any housing parts is necessary, preventing access to the bearing. In the case of a car, the wheel hub houses the wheel bearing, where a metal guard may cover it. Figure 8 shows a wheel bearing in its housing.
Once the bearing is accessible, it must be pressed or pried from its housing. Because it is designed to fit very snuggly, it is usually necessary to use a specialized tool, such as a bearing puller or press, to leverage the bearing against its housing. Alternatively, it may be possible to puncture the seal of the bearing and pry out the inner race, the balls, and then the outer race. Figure 9 shows an example of a bearing puller used in an automotive shop.
Once the user has removed the old bearing, they should also clean the inner walls of the housing. They should inspect the entire structure for abrasions, warping, and other kinds of damage that might impair its ability to hold the new bearing securely.
After inspection, the new bearing should be evenly pressed into the housing until it is snug and entirely in place. Next, the owner should replace and secure any covers or housings they removed by sliding the inner race of the newly installed bearing onto a shaft.
If the bearing is not pre-lubricated, it should at this point be lubricated with the correct lubricant. The amount of ball bearing grease or oil to be applied should be carefully determined. Too little will allow excess friction, while too much may cause damaging heat levels to accumulate in the lubricant during operation. Once the appropriate amount of lubricant has been determined, the applicator should be applied to the contact point between the cages and the races.
After the bearing is lubricated, ensure that it is rotating correctly. When it is clear that the new bearing is rotating correctly, it is time to remove the temporary support and allow the bearing to bear the machine's load. Once again, users should test the operation of the bearing. After a successful operation is confirmed, the ball bearing has been successfully replaced. Read our mounting, installing, and removing guide for more information.
When selecting a ball bearing, one should first consult official references for the target machine. Checking official references will ensure that the bearing chosen falls within the specifications recommended by the engineers who designed the machine. If this literature is not available, you may find parts suppliers who guarantee the compatibility of their parts. If these options are not available, one should select a bearing according to the following criteria.
The foremost considerations when selecting a bearing are the expected operating load directions and amounts. To determine these, a thorough understanding of the machine, its intended operation, and the relevant physics may be necessary.
If only radial loads are involved, then a standard, inner and outer race bearing may be used. If only axial, then a thrust bearing is likely the best choice. However, deep groove or angular contact bearings are likely necessary if radial-axial loads need to be supported.
When axial loads are involved, it is critical to specify whether they occur in just one or both directions. Single-row angular contact or thrust bearings may be appropriate for single-direction axial loads. But, for axial loads in both directions, double-row angular contact, double-row thrust bearings, or deep groove bearings should be used. Learn more about loads in our bearing overview.
The diameter of its outer race generally specifies the size of a ball bearing, the diameter of its inner race, also called its bore size, and its width.
The diameter of the outer race should ensure a press-fit into the housing or else to fall within clearance limitations.
The correct bore size should allow the bearing to clench the shaft tightly through a shrink fit. This process involves carefully heating the bearing, pressing it onto the shaft, and cooling back to size.
The width of the races should fit on the available axle space, between any snap ring grooves or shaft walls that may be present. When axial distance is limited, thin section bearings or proprietary designs may need to be considered.
The range of available ball bearing sizes includes one of the smallest ball bearings globally, with an outer diameter of fewer than 1.5 millimeters. It is so tiny that it can fit comfortably on a grain of rice. This bearing is intended for use in medical or dental equipment, such as a drill, where it might allow a bit to spin rapidly without wobbling as it bores precisely through a tooth or a bone. At the other end of the spectrum is a huge ball bearing with an outer diameter of over 6 feet and a dynamic load rating of over 280,000 lbs.
If installation conditions allow for a perfect right angle between the shaft and the plane of the bearing and the shaft is not subject to misalignment during operation, a standard ball bearing should be sufficient. However, a self-aligning bearing should be selected if installation conditions make it challenging to achieve perfect alignment or if the shaft is subject to temporary misalignment during operation. These include double-row self-aligning bearings and bearings with spherical housing washers, such as spherical thrust bearings.
The average speed at which the bearing will spin during operation is another critical factor that must be determined. This speed can be determined using sensor readings or calculations based on the dimensions of the machine and its production rate.
All else being equal, the conditions in the operating environment and dynamic load capacity should determine the bearing material.
Factors such as debris, corrosive elements, operating temperatures, and the presence of electrical current should have a limiting effect on the material options considered. Users generally prefer ceramics bearings over steel ball bearings in extreme operating temperatures and highly corrosive or electrically-charged environments. Aerospace projects often use this material because of its durability. However, if debris is likely and chipping the ceramics is a concern, a hybrid composition of ceramic balls and steel races may be better.
The material of the bearing should be selected to ensure a dynamic load capacity that will allow the bearing to achieve a sufficient number of working hours. Stainless steel is the go-to material for heavier loads, requiring greater capacities. Ceramics or the hybrid combination of ceramic balls and steel races are also good options for lighter to mid-range loads.
Depending on the machine operating environment, the initial cost of the bearing, and accessibility, a sealed, shielded, or open bearing should be selected. Users should select a sealed or shielded version for environments with significant amounts of debris or bearings that are difficult to access. These provide robust resistance to contamination and lubricant leakage, requiring no maintenance for the life of the bearing.
For more oversized, more costly bearings, operating in environments that are relatively free from debris and that are easily accessible, an open variety may be preferred. Open bearings allow for lubricant to be reapplied on an as-needed basis. By carefully monitoring the condition of the bearing and lubricating it when necessary, these bearings may last significantly longer than their sealed counterparts, whose inaccessible lubricant will eventually degrade.
The manufacturer's reputation, the quality of the ball bearing, and budget allocations should also be factored into consideration when selecting a suitable bearing.
In addition to examples encountered in the previous sections, there is a wide range of applications for ball bearings. Most devices with engines or other forms of rotation take advantage of the spatial efficiency of rotational motion to convert it into other forms of movement or energy by way of structures that require rolling bearings. Such applications include the following.
There are many more applications. If you can think of a device that has a fast rotating part or a rotating part that supports a heavy load, there is a high probability that you will find at least some models that use ball bearings to facilitate that rotation.
When a load is put onto the bearing, the race presses the ball at a single point, causing it to flatten slightly. This flattened area bears the burden in a manner consistent with the laws of physics.
Phillip Vaughn invented the modern ball bearing in . However, the first bearings were used in ancient times in the form of logs rolling underneath a load-bearing platform.
The most common material is stainless steel. However, ceramics are preferred for extreme environments, and hybrid bearings, consisting of steel races and ceramic balls, are also widely used.
Grease, oil, and synthetic oils are used primarily, though dry lubricants like graphite are also employed. Additionally, solid oil technology has recently emerged as a competitive alternative.
While environmental factors can affect the service life, a properly selected bearing will provide working hours consistent with the work hours formula discussed in the Selection criteria.
If a ball bearing is not permanently sealed, it may be possible to repair it. However, whether or not you should do so depends on the cost. Larger, more costly bearings are good candidates for repairs.
Sensors are now being used to monitor bearing operation, and the resulting data help anticipate when maintenance should be performed. Another development is that of superior lubricants.
If we break down the rotating mechanical equipment, systems, or mechanisms, different motions of their components are crucial for their functions. For instance, the blades rotate around the hub of a wind turbine to produce electricity. Do you know which device or parts control and dictate required motion within a mechanical system or machinery? The answer is a mechanical bearing. So, various types of bearings with different shapes, sizes, or designs achieve this by allowing motion in only one fixed direction.
Mechanical bearings also reduce the friction between moving parts. However, using the right bearing according to the requirement can only result in smooth and precise motions. Furthermore, we will discuss bearing uses and types, materials, and considerations for choosing the right bearing for your needs.
Contact of rotating metal to metal parts causes rapid wear in the contact surface. It lowers the lifetime of machinery and poses a risk to operational safety. So, the mechanical bearing on such joints or connections avoids contact and facilitates smooth motion. The reason behind this is the structure of the rolling element inside the bearing.
Typically, these rolling elements of ball or cylinder shape. They move in a rolling motion, and we know that rolling is a low-friction process than sliding.
In the ball bearing, rolling elements are the spherical balls. These balls between two bearing races can support both radial and axial loads. Meanwhile, a component called retainer separates the balls and holds them with uniform spacing. These are typically made with roller-bearing steel or stainless and , which carry and pass the loads into the inner ring of the bearing.
Next, you can find different ball bearing types based on load direction, raceway design, specific function, and size that can fulfill diverse application requirements.
Like its name, deep-groove ball bearings contain deep grooves in inner and outer raceways to hold the balls. This simple design makes it versatile and applicable in various applications, from electric motors to gearboxes and water pumps.
Consequently, deep groove bearings can handle heavier loads and are suitable for high-speed rotations. The compact structure also facilitates the efficient use of space within the machinery or systems. However, they are sensitive in case of misalignment possibility.
When to Use: High-speed machinery like turbines or motors & limited space applications.
This type of ball bearing contains a cage structure with two rows of balls at a uniform distance between the outer and the inner race. In case of any static or dynamic misalignment, the outer race allows to adjust the bearing position accordingly to correct it.
The prime advantage of self-aligning ball bearings is that they can self-correct the angular misalignment for seamless operation. They are also good at shock and vibration absorption. On the other hand, the complexity increases the bearing cost, and they have limited load capability.
When to Use: If the machinery or systems have misalignment possibilities and for moderate speeds and loads.
In the angular contact ball bearing, balls transfer the forces from the outer to the inner ring at a specific angle (the contact angle). It is possible with a displacement of races to each other. That’s why, angular types of bearings are also known as angled bearings. Moreover, they can handle higher loads and are compatible with high-speed operations.
Although single-row, double-row, and sealed options make angular contact bearing versatile, it can possess higher friction at higher contact angles.
When to Use: If the forces are combined (axial and radial) and heavy.
Thrust ball bearings are simple and low-cost bearings for axial loads. Their structure involves balls in a cage surrounded by two rings, the inner race typically connects the rotating shaft. Consequently, they come in two variations: Single direction and double ball bearing thrust bearings. In double-direction configurations, the balls remain in an alternating pattern or position between the rings.
These thrust bearings can accommodate high-speed axial loads. They are also simple to install and cost less than the other bearings.
Disadvantages: Limited to axial load directions and prone to misalignment & ball skidding.
When to Use: Thrust-bearing applications with dominant axial loads like machine tool spindles and crane hooks.
Miniature type refers to the small-sized micro ball bearings. They are for small spaces and precision load handling. You can imagine how small they can be from the fact that the overall diameter can only be less than 20 mm (according to EU standards).
The small designs of bearings in this form open the use of ball bearings in precise applications like electronics and medical equipment. Also, miniature bearings produce minimal noises during operation.
Disadvantages: Low load capacity and vulnerable to contamination.
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When to Use: For small machinery & precision applications.
This type of bearing contains a thin layer of inner and outer race so they can fit in minimal space. The rolling element could be a ball or cylindrical bars. Although the weight is less in thin-section bearings, they do not compromise with the accuracy and friction-reducing capability. Additionally, various configurations, including open, shielded, and sealed section bearings are available in the market for different applications.
Disadvantages: Lower load capability and misalignment sensitivity.
When to Use: High-performance applications like defense, aerospace, and electronics.
A flanged bearing contains an extended flange on the outer race of the bearing radially outward. The flange is for a strong attachment of bearing on the frame or machine wall. For that, the flange also includes a mounting arrangement in it like a bolt or screw. Predominantly, flanged bearings are for radial loads, but they can also handle low levels of axial stress.
Disadvantages: Limited load capability and the flange can interfere with the other components, especially in small-size machinery.
When to Use: For high speeds with low loads and excessive vibration scenarios.
Thrust bearings are mainly for high axial loads, whereas ball bearings are mainly for radial loads. The structure of the ball or other rolling element arrangement includes an alternative positioning between two rings. It increases the exposure surface area to the stress, which improves the axial load-bearing capacity.
There is also a similarity between the thrust bearing vs. ball bearing. A thrust bearing can have a ball as the rolling element. However, this is not always the case. It can also have a roller or other rolling element.
Let’s see the differences in these two bearing types through a comparison table;
As the name indicates, roller bearings contain rollers of different shapes to transmit stress. The shape can be cylindrical, spherical, conical, or even a needle. The main reason for using rollers, instead of balls is to increase the exposed surface area for higher loads. The rolling motion of rollers carries the rotating load of the shaft.
Moreover, the variations of roller bearings support the radial, axial, or combined loads. Similar to ball bearings, this bearing kind minimizes friction and optimizes the performance of moving parts.
Here are the common variations of roller bearings.
This kind of roller bearing involves both a tapered inner race (called a cone) and an outer race (called a cup) with tapered rollers arranged in a cage between them. The contact angle (tapered angle) of the outer ring typically ranges from 10° and 30°.
Here, the tapered shape can uniformly distribute the heavy axial load of the shaft, and it can also accommodate the radial loads along with it. The compact design makes them consolidated bearings and saves space. Moreover, tapered roller beading provides greater stability and can adjust a certain level of misalignment itself.
Disadvantages: Complexity, relatively higher prices, and limited load capability in some designs.
When to Use: Heavy equipment with high axial & radial loads, such as railway systems and mining tools.
The structure of roller bearings consists of spherical rollers of two rows in a cage divided by a separator. The rolling of these elements reduces the friction and supports large loads from the shaft. Additionally, spherical roller bearings have the capability of self-adjusting the angular misalignment of the shaft concerning the outer ring.
Disadvantages: Not suitable for high-speed applications.
When to Use: Misalignment-prone applications with heavy loads and moderate to high speeds like off-road cars & marine propulsion.
The thrust roller or spherical roller thrust bearings include a similar structure to the thrust ball bearing, except for lengthy spherical rollers instead of balls. These are for the unidirectional heavy axial loads and a considerable amount of radial loads.
These roller bearings also permit misalignment and are flexible with the operating speeds, so are popular in industrial setups.
Disadvantages: Only flexible with heavy loads in the axial direction. Next, the misalignment increases the friction.
When to Use: As the industrial bearing, in high-duty applications. For instance, turbines and compressors.
The cylindrical rollers can carry higher radial loads because of linear contact between rollers and rings. However, they also support a moderate level of axial forces. Meanwhile, the cylinder roller configuration can have one or multiple rows. The large surface contact of the cylindrical roller with the outer race uppers the load-bearing limit. But, at the same time, it increases the friction.
Disadvantages: Only focuses on the radial load and sometimes the stress can be concentrated on the edges of rollers.
When to Use: In high radial load conditions, like tool spindle and drilling rigs. Thor half-shape variation is also popular as a saddle bearing in hydraulic pumps.
The structure and working of needle roller bearings are similar to the cylindrical roller bearings. The only difference is the size of the cylindrical rollers inside the bearing needle bearings are tiny roller bearings. Cylinders are very thin with small diameters as compared to the length. Here, the diameter is ≦6 mm is only considered as the needle. The lower-weight roller also allows high speed. So, these types of bearings provide higher radial-load support in a compact space.
Disadvantages: Edge loading & relatively higher friction.
When to Use: Application with variable loads and jerk. For instance, piston pin bearing.
The cross roller bearing consists of cylindrical-shaped rollers in a cross pattern. It means the alternative rollers intersect each other at 90°. This arrangement of rollers promotes rigidity and precision in handling axial and radial stresses. Consequently, cross-rollers are ideal for rotational motion control.
Disadvantages: Complex installation and risk of misalignment.
When to Use: For heavy radial loads and accurate motion control.
Plain bearings are the simplest form of bearing with no rolling elements, just a cylindrical bore to hold the shaft or similar components. They are also known as the sleeves or bushes. The plain surface of the plain bearing stabilizes the heavy radial & axial load and also lowers the friction. So, the use of low-friction material is critical to making plain types of bearings like brass or hard polymer. Additionally, they can be both lubricated and dry types.
Furthermore, the plain bearings come in various configurations like cylindrical, thrust washer, flanged, and sliding plates. Moreover, the bearings can also include features like grooves, holes, notches, or tabs in the contact surface to reduce friction and support the application requirement.
Advantages of Plain Bearings
Disadvantages of Plain Bearings
When to Use Plain Bearings?
The pain bearings are best for low-speed & heavy-load mechanical operations where the risk of misalignment and oscillation is a critical issue like industrial cranes or agricultural machinery. Also, these are excellent choices for bespoke bearings, where cost is a big concern.
First, the rolling elements’ presence is the structural difference in plain bearing vs ball bearing comparison. Another point is that ball bearings can be applied in more areas due to diverse configurations. For more specific differences, let’s look at the comparison table below;
The fluid bearings replace the metallic bearings with a thin layer of fluid, air, gas, or lubricant between the housing and rotatory surface. While applying fluid bearings, moving parts don’t contact each other. Instead, the fluid properties hold the load and provide smooth motions to the components. The fluid film is injected into the joint with dedicated holes or channels.
Furthermore, hydrostatic and hydrodynamic are two bearing kinds of this category, which are widely used in precise & high-speed machines to reduce friction and handle heavier loads.
Hydrostatic types of bearing work on the principle of pressurized fluid. It says that if fluid is injected under high pressure between moving parts, it reduces the friction and maintains the relative motion. Here, external pressure is essential for maintaining the operation. Meanwhile, the precision depends on the gap control.
Advantages of Hydrostatic Bearings
Disadvantages of Hydrostatic Bearings
When to Use?
Hydrostatic bearings are excellent choices for both rotary and liner motions. They can control the motions in precision applications like machining spindles and gas turbines. Additionally, sensitive applications like aircraft control systems also use these types of fluid bearings.
First, let’s define a term related to bearing part called “journal”. It refers to the portion of the shaft that remains inside the housing. Hydrodynamic bearings provide load support and low friction with the use of this journal. The fluid makes the bearing film using the relative motion of the journal with the contact surface. The performance of this hydrodynamic bearing type relies on the rotation speed, fluid viscosity, and proper alignment.
Advantages of Hydrodynamic Bearings
Disadvantages of Hydrodynamic Bearings
When to Use?
Hydrodynamic bearings are best for moderate to high-speed applications like pumps or turbines. They are also preferred for marine systems and industrial equipment.
The magnetic bearings use electromagnetic force to rotate or suspend a rotor in a fixed position. The general stricture of a magnetic bearing includes an electromagnetic field inside the bearing, typically wounded wires on ferrous material. Once the magnetic field is activated, the force itself levitates the rotor component and is fixed for optimal rotor dynamics. So, the moving rotor makes no contact with the surface. This makes magnetic bearings capable of operating at extremely high speeds and loads
Furthermore, there are two types of magnetic bearings;
The active magnetic bearings use active control mechanisms to stabilize and control the position of a rotating shaft. The integrated sensors and feedback control mechanism monitor and process the real-time data, and the control unit adjusts the positioning accordingly.
The real-time monitoring and self-positioning advantage of active magnetic types of bearings facilitates high precision in motion control and system stability. Next, the contact-less moving produces minimal friction and keeps the system efficient and durable.
On the other hand, active kinds of bearings have a few drawbacks, such as setup complexity, high energy consumption, and thermal sensitivity.
When to Use?
In passive magnetic bearing, there is no active system or feedback mechanism to adjust the motion. Instead, the permanent magnets inside the bearing are arranged in a way that their repulsive and attractive forces levitate and control the position & rotation.
These magnetic bearing requires less maintenance and are cheaper than the active ones. They are simple in design and operate silently, whereas the use of permanent magnets makes them more reliable. If we talk about their disadvantages, passive magnetic bearings have lower load capacity, and the absence of real-time feedback gives less control over the operation.
When to Use?
Bearings are necessary for any machines, mechanical systems, and tools with a rotating motion to support the operating load and reduce friction, vibration, and noise. Thus, they can be found in numerous applications, including automotive, aerospace, industrial machinery, and consumer items.
Automotive
The automotive vehicle contains several bearing types in different sections and components. The automotive bearings are responsible for supporting the load and facilitating the motions in different parts.
Examples;
Aerospace and Aviation
The bearings are essential in the safety, flight control, performance, and reliability of aerospace applications. You can find bearings in aircraft, missiles, rockets, and other related equipment. Here are the uses of some aviation bearings;
Industrial Machinery and Equipment
The rotational motions are the key to the functionality of industrial machinery and equipment. They utilize different types of bearings for the smooth movement of rotating components.
Consumer Products
We can also see the different shapes & sizes of bearings in consumer products, from washing machines & refrigerators to furniture items.
First, you need to consider the load-handling capacity of the bearing. It often consists of axial, radial, or combined loads (moment) rating to gauge the load capacity. Here, the capacity should match the requirements of the application. For example, heavy-duty appliances like washing machines or power tools require bearings with high load capacities.
All the bearings do not support the high-speed shaft or rotor. Types of bearing like thin-section bearing support very low speeds, whereas roller & deep-groove metal bearings can operate at high rotational speeds. Furthermore, you can reference the ISO standard for “bearing speed guidelines” to check which bearing can match the intended speed.
It defines the capability of the bearing to maintain a steady position and speed for the shaft or any other rotor. So, identify allowable radial and axial oscillations in your application and look for the bearing with sufficient rotational accuracy. Some applications like aircraft control or electronics might need a high level of accuracy, but other areas like furniture might not need the same accuracy.
The condition of the operating environment like moisture, dust, chemical exposure, temperature, and stress, also affects the selection of bearing. For example, marine applications might require high bearings with highly corrosion-resistant materials. So, list all the operating scenarios and look for the bearing that can operate in that condition without compromising the efficiency.
Precision metallic bearings are essential in applications like electronic devices or audio equipment for high performance and minimal vibration. So, consider the noise level of the bearings and check whether that suits the installation scenarios or not. For instance, deep-groove bearings produce very low noise.
It refers to the available space within the machine or design to accommodate itself. Even a slight constraint of space for bearing affects the overall performance and safety. So, choose bearings that not only fit but do not interfere with the operation of other companies. For instance, miniature & needle forms of bearings are flexible with the space, but many are not.
Rigidity means stiffness of the bearing structure and its ability to maintain stable and precise operation under load. The rigidity of the bearing also affects the uniformity of load distribution. Therefore, consider the potential load during operation and rigidity to maintain the stability under that load. Also, some specific bearings offer a high level of rigidity due to their structure, such as tapered bearings & angular-contact bearings. Meanwhile, the bearing material properties also influence the overall rigidity of the bearings.
The vibration of the bearing while working affects both performance and user experience. Some products like consumer items need bearings with minimal vibration for smooth operations. So, choose the bearings with vibration within the allowable range according to the requirement.
Although metal and alloys are popular as bearing materials, they also can be made with composite, rubber, and plastics. The bearing material is a critical aspect of the performance and durability of bearings. The material properties like hardness, friction-coefficient, and strength directly impact the bearing or machine’s performance.
The non-metallic bearing materials are mainly used in specific scenarios like applications requiring chemical inertness, electrical insulation, and low weights. Here are the kinds of common non-metallic materials and their properties.
The mechanical bearings are essential components of rotatory hardware, machines, and setups. The main purpose of installing bearings is to lower the friction and support the operational forces, whether they are plain, ball, roller, fluid, or magnetic bearings.
However, only the right type of bearing according to requirements can achieve the intended results. Therefore, considering factors like load capacity, vibration, noise, size, and other aspects while choosing the types of bearings can optimize the performance during the operation.
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