Exploring about bearings

1. DESIGN CHARACTERISTICS
OF BEARINGS

2. Machine bearings are components that support the
movement of rotating parts within machinery. They reduce
friction between moving parts and facilitate smooth
rotation. Bearings come in various types, such as ball
bearings, roller bearings, and plain bearings, each
designed for specific applications. They play a crucial role
in ensuring efficient and reliable operation of machines by
minimizing wear and allowing for smooth motion.

4. Ball Bearing
A ball bearing is a type of rolling-element bearing that serves three main functions while
it facilitates motion: it carries loads, reduces friction and positions moving machine parts.
Ball bearings use balls to separate two “races,” or bearing rings, to reduce surface
contact and friction across moving planes. Most ball bearings are made of a type of steel
known as high carbon chromium steel, often called chrome steel. This is used for
reasons of cost and durability. Common materials used in constructing ball bearings
include carbon steel, stainless steel, chrome steel, brass, aluminum, tungsten carbide,
platinum, gold, titanium, plastic. Other less common materials include copper, monel, k-
monel, lead, silver, glass, and niobium.
Advantages:
• Ball bearings are compact and have a lightweight design.
• Cost effective compared to roller bearings.
Disadvantages:
• Lower load capacity when compared to roller bearings.

6. Roller Bearing
Roller bearings are used to replace sliding movement with low friction, rolling motion in
rotary applications. The principal types of roller bearings are cylindrical, spherical, and
tapered. In general, roller bearings offer higher load capacities than ball bearings of the
same size. One of the major material that has been used in constructing roller bearings
is chrome SAE 52100 bearing steel. This material has excellent wear resistant capacity
and a Rockwell hardness of about 64 HRC. Bearings made of chrome steel can function
at temperatures up to 120°C, and upon heat treatment, they can even go as high as
220°C.
Advantages of rolling bearings
1, the friction resistance and the power consumption are small, the mechanical efficiency
is high, and is easy to start.
2, size standardization, interchangeability, easy to install and disassemble, easy to
repair.
3.The structure is compact, the weight is light, and the axial size is narrower.
4. High precision, large load and long service life.
5. Some bearings have the performance of automatic heart adjustment.

7. 6. It is suitable for mass production, the quality is stable and reliable, and the production
efficiency is high.
7. The friction torque of the transmission is much lower than that of the fluid dynamic
pressure bearing, so the friction temperature rise and the power consumption are low.
8. The axial size is less than the traditional fluid dynamic bearing.
9. The combined load of radial and thrust can be borne simultaneously.
10. Within a large load – velocity range, the unique bearing design can achieve excellent
performance.
Disadvantages of rolling bearings
1. The noise is great.
2. The structure of the bearing seat is complex.
3. The cost is high.
4. Even the bearings are lubricated well, installed correctly,well sealed, and the operation
is normal, they will eventually fail because of the fatigue of the rolling contact surface.

9. Plain Bearing
Plain bearings operate on the principle of sliding friction and employ no rolling elements;
they are generally quieter than anti-friction bearings as they have no moving parts. Plain
bearings may be used for rotational or linear applications.
Plain bearings must be made from a material that is durable, low friction, low wear to the
bearing and shaft, resistant to elevated temperatures, and corrosion resistant.
Babbitt
Babbitt is usually used in integral bearings. It is coated over the bore, usually to a
thickness of 1 to 100 thou (0.025 to 2.540 mm), depending on the diameter.
Bi-material
Bi-material bearings consist of two materials, a metal shell and a plastic bearing surface.
Common combinations include a steel-backed PTFE-coated bronze and aluminum-
backed Frelon.

11. Bronze
A common plain bearing design utilizes a hardened and polished steel shaft and a
softer bronze bushing. The bushing is replaced whenever it has worn too much.

12. Cast iron
A cast iron bearing can be used with a hardened steel shaft because the coefficient of
friction is relatively low. The cast iron glazes over therefore wear becomes negligible.
Graphite
In harsh environments, such as ovens and dryers, a copper and graphite alloy,
commonly known by the trademarked name graphalloy, is used. The graphite is a dry
lubricant, therefore it is low friction and low maintenance. The copper adds strength,
durability, and provides heat dissipation characteristics.

13. Jewels
Known as jewel bearings, these bearings use jewels, such as sapphire, ruby, and garnet.
Plastic
Solid plastic plain bearings are now increasingly popular due to dry-running lubrication-
free behavior. Common plastics include nylon, polyacetal, polytetrafluoroethylene
(PTFE), ultra-high-molecular-weight polyethylene (UHMWPE), rulon, PEEK, urethane,
and vespel (a high-performance polyimide).

16. Integral Plain Bearing
Integral plain bearings are built into the object of use as a hole prepared in the bearing
surface. Industrial integral bearings are usually made from cast iron or Babbitt and a
hardened steel shaft is used in the bearing.

17. Bussing
A bushing, also known as a bush, is an independent plain bearing that is inserted into a
housing to provide a bearing surface for rotary applications; this is the most common
form of a plain bearing. Common designs include solid (sleeve and flanged), split, and
clenched bushings.
Clenched Bushing Flanged Bushing

18. Two Piece Bearing
Two-piece plain bearings, known as full bearings in industrial machinery, are commonly
used for larger diameters, such as crankshaft bearings. The two halves are called shells.

19. “Wrapped bushes” refer to a collection of metal bushings, washers, and plates that
have a polymer coating on their operating surfaces. There are also dry plain wrapped
bearings that are made of materials such as PTFE (Teflon), graphite/metal, and
ceramic.

20. A flexure bearing is a category of flexure which is engineered to be
compliant in one or more angular degrees of freedom. Flexure bearings
serve much of the same function as conventional bearings or hinges in
applications which require angular compliance. However, flexures require
no lubrication and exhibit very low or no friction.
Advantages of flexure bearings include simplicity, low friction, and absence
of lubrication requirements.
Disadvantages may involve limited load capacity and susceptibility to wear
over time.

22. Needle Bearing
Compared to ball bearings and ordinary roller bearings, needle bearings have a greater
surface area in contact with the races, so they can support a greater load. They are also
thinner, so they require less clearance between the axle and the surrounding structure.
Advantages of needle bearings include high radial load capacity, compact design, and
suitability for applications with limited space. They also offer low friction and high
rotational accuracy. However, needle bearings may have higher manufacturing costs and
can be sensitive to misalignment, impacting their durability. Additionally, they may require
proper lubrication for optimal performance.

24. Linear Bearing
A linear-motion bearing or linear slide is a bearing designed to provide free motion in one
direction. There are many different types of linear motion bearings. Motorized linear
slides such as machine slides, X-Y tables, roller tables and some dovetail slides are
bearings moved by drive mechanisms.
Linear bearings offer smooth and precise motion in applications like machinery and
automation. Advantages include low friction, high load capacity, and minimal wear due to
linear motion. They’re also compact and can handle both radial and axial loads.
However, linear bearings may suffer from issues such as sensitivity to contamination,
requiring regular maintenance. They might produce noise during operation, and certain
types can be more expensive than traditional sliding bearings. Additionally, proper
alignment is crucial for optimal performance.

26. Fluid Bearing
Fluid bearings which are often oil bearings are useful and necessary in the basic rotating
machinery used in industry. They allow: Optimization of impedance to the rotor for
stability; passage of critical speed and normal function with vibrations and force
transmitted to low-amplitude bearings.
Advantages of fluid bearings include low friction, reduced wear, and potentially longer
lifespan due to minimal contact between surfaces. They also offer smooth operation and
high load capacity.
Disadvantages include the need for a continuous supply of fluid, potential leakage
issues, and sensitivity to contaminants that may affect performance. Additionally, the
initial setup and maintenance can be more complex compared to other bearing types.

28. Magnetic Bearing
A magnetic bearing is an oil-free bearing system that uses electromagnetic forces to
maintain relative position of a rotating assembly (rotor) to a stationary component
(stator).
Advantages of Magnetic Bearings:
1. No Physical Contact: Magnetic bearings operate without physical contact, reducing
friction and wear, leading to minimal maintenance requirements.
2. High Speeds: They can handle high rotational speeds, making them suitable for
applications with rapid motion.
3. Low Vibration: Magnetic bearings provide smooth and vibration-free operation,
contributing to improved precision and reduced mechanical stress on components.

29. Disadvantages of Magnetic Bearings:
1. Complexity: The design and control of magnetic bearings can be complex, requiring
sophisticated technology and expertise.
2. Cost: Magnetic bearing systems can be expensive to manufacture and install, limiting
their widespread adoption in certain applications.
3. Power Consumption: Continuous power is needed to maintain the magnetic field,
which can result in increased energy consumption compared to traditional bearing
systems.

31. Tapered Roller Bearing
A tapered roller bearing is a unit that consists of both tapered raceways (inner and outer
rings), and tapered rollers. The construction is intended for combination loads, such as
dual acting axial and radial loads.
Tapered rolling bearings have several advantages, such as handling both radial and
axial loads, efficient at high speeds, and facilitating accurate alignment. However, they
may suffer from disadvantages like increased complexity, higher manufacturing costs,
and potential for increased friction at higher speeds. The choice depends on specific
application requirements.

33. Cylindrical Roller Bearing
Cylindrical roller bearings (CRBs) have a simple structure with their cylindrical rollers in
linear contact with the raceways. They offer high load capacity under primarily radial
loads. Low friction between the rollers and ring ribs makes these bearings suited for high
speed rotation.
Cylindrical roller bearings offer advantages like high radial load capacity, good speed
performance, and design versatility. However, they may have limitations such as lower
axial load capacity compared to some other bearing types and sensitivity to
misalignment. The suitability depends on the application’s specific needs and operating
conditions.

35. Bearing Lubrication
Bearing lubrication is vital for preserving the performance and lifespan of rolling element bearings.
Lubrication helps separate moving parts relative to one another, such as rollers and raceways or balls, to
prevent wear and tear and friction.
Bearing lubrication serves several functions to keep bearings performing their best such as:
• Protecting surfaces from corrosion
• Sealing against contaminants
• Creating a barrier between rolling contact & sliding surfaces
• Providing heat transference

36. Advantages of bearing lubrication include reduced friction, heat dissipation, and wear
prevention, leading to prolonged bearing life. However, disadvantages can arise from
over-lubrication, causing increased friction, overheating, and potential damage to the
bearing. Proper lubrication is crucial for optimal performance.

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