There are wide range of linear motion products in the market
so it is difficult to choose right product for our business. In this article,
we will look at the different types of products available for rolling elements,
and the advantages, disadvantages and limitations.
What is mean by Linear Motion Products?
The main objective of linear motion products is to move from
one direction to another along a straight line. Normally this is done using
rolling element bearings. Traditionally, these rolling elements are balls or
rollers, but at present some linear bearings are known as "normal"
bearings because they do not contain rolling elements. These plain bearings are
simply plastic or ceramic bearings and are sometimes coated with PTFE or
plastic impregnated with oil to reduce sliding friction.
It is possible to achieve linear motion without bearing but
moving a load without a bearing requires a lot of efforts.
Linear bearings can be moved in various ways. It can drive
with screws, straps, chains, rack and pinions, or
simply push them with your hands also.
What is the Range of Products??
For the sake of simplicity, several linear motion products are
discussed according to type.
Linear ball bearings provide the least friction. The two
main products are the recirculating ball bushes and the motion guidance
systems.
1.The re-circulation
ball bearings are traditional linear bearings and are used with hardened
and polished shafts. The friction of the ball is very low because the contact
area of the point is very small. However, small contact areas produce large
forces on the shaft, so it is essential to use only on hardened shafts.
2. Motion guidance systems (also known as ball guides and
linear guides) use recirculation balls but operate on the profiles. The ball
grooves in these rails are generally in the form of a Gothic arch to maximize
the load capacity. Again, the rails must be hardened to prevent the high load
balls from becoming deformed. These systems are generally more forgiving at the
time than conventional linear recirculating bearings.
Roller bearings have a higher rated load capacity than ball
bearings of equivalent size. But they are less tolerant of lateral forces.
Roller bearings are mainly used as chain rollers, but can also be used for
cross roller guides.
1.A track bearing is a bearing that rolls the outside
diameter along the track. Normally, rolling elements include rollers, but can
sometimes contain balls (usually when radial load capacity is required). The
caterpillar bearings are very versatile and come in a variety of styles. The
simplest is a rigid and complete complementary roller bearing while the other
profiles the outer ring to match a
molded (sometimes cured) rail. It can be joined using a spike, a threaded stud
or a weldable hub. Other designs include secondary shaft rollers to
accommodate side loads.
2.The roller
guides are similar to the ball
guides, but offer a greater load capacity than the equivalent size versions of
the ball. Due to their compactness and precision, they are often used in
medical applications.
3.The crossed roller slide provides very high precision and
a high load capacity. However, due to the nature of the design, it is
susceptible to contamination and, as a result, is often used in clean room or
vacuum applications.
A plain bearings (or bushes) have evolved rapidly in the
last two decades with the development of low friction plastics. Normally the
bearings are usually plastic or ceramic. The coefficient of friction is
reduced, but the coefficient of friction is generally much higher than that of
rolling element bearings.
1.Linear plastic bearings are cheaper and reduce friction
than using two similar materials together. Because there are no rolling
elements, there is little or no concern about product contamination due to
dust, dirt and debris. Nowadays, a wide range of plastics offers a variety of
benefits.
2.Linear ceramic bearings offer characteristics similar to
linear plastic bearings. They are quiet and soft, and are generally the same
size as conventional recirculating linear bearings and do not need lubricant.
There is also a combination of movement of rotation and linear movement.
Moderate :-
There are many factors to consider when choosing a linear
motion product. The range of products available is extensive and each product
is available in a variety of shapes and sizes. Obviously, the price is always
an element, but each system has advantages and disadvantages.
Factors to be consider while selecting Linear Motion Product.
1.Load Capacity
2. Accuracy
3.Support arrangement
4. Environment
5. Resistance to corrosion.
6.Size and Scale
7.Friction
Advantages and Disadvantages Of products :-
1.Ball Bushing:-
Advantages of Ball Bushing:
· High accuracy
· Very low friction
· Harder than plain bearings.
· You can make small moments.
· Long life
· High speed
Disadvantages Of Ball bushing:-
- Do not like contamination
- Need lubrication
- Must run on hardened shafts
- Some noise
2.Ball Guide:-
Advantages of Ball Guide:-
- High accuracy
- Carry large moments
- Compact
- Very low friction & start-up friction
- Miniature size option
Disadvantages of ball guide:-
- Do not like contamination
- Need lubrication
- Rail can be expensive
Advantages of Cross Roller Guide
- High load capacity
- Very high accuracy
- Compact design
- Low friction
Disadvantages of Cross Roller Guide
·
- Expensive
- Do not like contamination
- Rails must be protected with bellows
- Fixed stroke
4.Roller Linear
Guides:-
Advantages of Roller Linear Guides:-
- Higher load capacity than ball guide equivalent
- High accuracy
- Compact Design
- Low friction
Disadvantages of Roller Linear Guide:-
- Expensive
- Don’t like contamination
- Not as readily available as Ball Guides.
When assigning a linear motion product, you must take into
account the advantages and disadvantages of each product. Special attention
must be paid to friction because the coefficient of sliding friction (ordinary
bushing) is significantly higher than the rolling friction (balls and rollers).
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