LINEAR MOTION SYSTEMS
LINEAR MOTION SYSTEMS
LINEAR MOTION SYSTEMS
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Simplicity ® Ball Bearings<br />
Technical Information<br />
Linear Motion Systems<br />
LOAD RATING AND LIFE EXPECTANCY<br />
The life (L) of a linear bushing can be obtained from the<br />
following equation with the basic dynamic load rating and the<br />
load applied to the bush:<br />
L : Rated life (km/in.)<br />
C : Basic dynamic load rating (N/#)<br />
P : Working load (N/#)<br />
fw : Load coefficient<br />
fH : Hardness factor (see page ???)<br />
fT : Temperature coefficient (see page ???)<br />
fC : Contact coefficient (see page ???)<br />
The lifespan (Lh) of a linear ball bushing in hours can be<br />
obtained by calculating the traveling distance per unit time.<br />
The lifespan can be obtained from the following equation if<br />
the stroke length and the number of strokes are constant:<br />
LOAD RATING<br />
Basic Dynamic Load Rating (C) -<br />
This term is arrived at based on an evaluation of a number<br />
of identical linear systems individually run in the same<br />
conditions, if 90% of them can run with the load (with a<br />
constant value in a constant direction) for a distance of 50 km<br />
without damage caused by rolling fatigue. This is the basis of<br />
the rating.<br />
Allowable Static Moment (M) -<br />
This term defines the allowable limit value of static moment<br />
load, with reference to the amount of permanent deformation<br />
similar to that used for evaluation of basic rated load (Co).<br />
Static Safety Factor (fs) -<br />
This factor is used based on the application condition as<br />
shown in Table 1.<br />
TABLE 1 - STATIC SAFETY FACTORS<br />
CONDITION OF USE<br />
LOW LIMIT OF fs<br />
When the shaft has less defl ection and shock 1 to 2<br />
Lh : Lifespan (hr)<br />
L : Rated life (km/in.)<br />
s : Stroke length (m/in.)<br />
n 1 : Number of strokes per minute (cpm)<br />
When elastic deformation should be considered<br />
with respect to cantilever load<br />
When the equipment is subject to vibration<br />
and impacts<br />
2 to 4<br />
3 to 5<br />
Basic Static Load Rating (Co) -<br />
This term defines a static load such that, at the contacting<br />
position where the maximum stress is exercised, the sum of<br />
the permanent deformation of the rolling elements and that of<br />
the rolling plane is 0.0001 time of the diameter of the rolling<br />
elements.<br />
RELATION BETWEEN BALL CIRCUITS AND LOAD RATING<br />
The Simplicity ® linear ball bearings are constructed so that<br />
the ball circuits are spaced equally. The load rating varies<br />
according to the loaded position. The load ratings of the linear<br />
ball bearings from the dimensional tables are per track and<br />
increased loading can be achieved by equally sharing the load<br />
between the tracks.<br />
The following table shows the increased value by the number<br />
of ball circuits in such cases:<br />
Number<br />
of Rows<br />
Co<br />
Load Rating<br />
Specified on<br />
the Tables<br />
Co max<br />
Maximum<br />
Load Rating<br />
4 5<br />
6<br />
Co<br />
Co max<br />
Co<br />
Co max<br />
Co<br />
Co max<br />
Technical Information<br />
Load Ratio<br />
Co max /Co<br />
NOTES:<br />
1.414<br />
1.463<br />
1.280<br />
3 track bearing is equal.<br />
Open bearing load is de-rated by 50% if going against the opening.<br />
The data and specifi cations in this publication have been carefully compiled and are believed to be accurate and correct. However, it is the responsibility of the user to<br />
determine and ensure the suitability of Pacifi c Bearing® products for a specifi c application. Pacifi c Bearing’s only obligation will be to repair or replace without charge,<br />
any defective components if returned promptly. No liability is assumed beyond such replacement. *Consult www.pacifi c-bearing.com for the latest technical updates.<br />
800.962.8979 • www.pacific-bearing.com 87