| When determine a model that would best suit for service conditions
of a linear motion system, the load rating and travel life of the
modell must be considered. To consider the load rating, you should
know the static safety factor of the model, which is calculated based
on the basic dynamic load rating, and you need to check if the values
thus obtained meet your requirements. |
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| Tere are two basic load ratings of a linear motion system : basic
static load rating(Co), which sets the static load allowance limit,
and basic dynamic load rating(C), which is using for calculating travellife. |
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| If a linear motion system, wheter at rest or in motion, receives
an excessive load or large impact, a local permanent deformation develops
the raceway and rolling elements. And if the magnitude of the permanent
deformation exceeds a certain limit, it hinders the smooth motion
of the linear motion system. The basic static load rating refers to
a static load in a given direction with given magnitude, which total
permanent deformation of rolling elements and raceway at the contact
area is approximately 0.0001 of the rolling element diameter. In a
linear motion system, the basic static load rating. For the rating
values of individual linear motion systems, see the respecticve specification
table in this catalog. |
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| A linerar motion wywtem may possibly receive an unpredicable external
force due to the vibration ir impad while it is at rest or in motion,
or intertia as a result of starting and stopping. It is, therefore,
necessary to consider the static safety fad or against operating loads.
the static safety factors(fs) indicates the ratio of a linear motion
system load carrying capacity(basic static load rating, Co)to the
load exerted there on. |
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| To calculate a load exerted on the linear motion system, the mean
load for calculating the service life and the maximum load for calculating
the static safety factor must be obtained in advance. A system can
receive unexpected load when it is subject to frequent starts and
stops, placed under machine loads, or when the severe moment is applied
by overhabging loads. When selecting the correct type of a linear
motion system for your application, be sure that tpe you are considering
canbear the maximum possible load when stopped and in opperation.
The table below specifies the standard values for the static safety
factors. |
| Machine
used |
Locading
conditions |
fs
lower limit |
| Ordinary
Industrial Machine |
Receives no vibration or impact
Receives vibration or impact |
1.0~1.3
2.0~3.0 |
| Machone tool |
Receives no vibration or impact
Receives vibration or impact |
1.0~1.5
2.0 5~7.0 |
| For
large radial loads |
 |
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|
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| The basic dynamic load rating (C) refers to a load in agiven direction
with given magnitude such that when identical linear motion system
in a group are interlocked with one another under the same conditions,
the nominal life(L) of the systems is 50km (L=50km) if the systems
use balls, and 100km(L=100km) if they use rollers. The basic dynamic
load rating(C) is used to calculate the service life of a set of linear
motion systems, which are interlocked with one another in response
to a load. For rating values of individual linear motion systems,
see the respective specification tables in this catalog. |
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| The service lives of lonear motion systems more or less vary from
system even if they are manufactured to the same specifications and
remain in service under the same operating conditions. Hence a guideline
for determining the service life of a linear motion system is given
based on nominal life, Which is defined as follews. The nominal life
referts to the total running distance that 90% of identical linear
motion systems in a group, when interlocked with one another under
the same conditions, can anhieve without flaking develops. The nominal
life(L) of a linear motion system can be obtained from the basic dynamic
load rating(C) and load imposed(P) using the follow equations. |
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| The travel life of the Linear Bushing can be obtained using the
following equation |
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| Once nominal kife L is obtained using this equations, the Linear
Bushing service life can be calculated using the following equations,
if the stroke length and the number of reciprocating cycles are constant |
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