TERMS OF LINEAR GUIDE
11 Major factors:
a. Load and Life (L)
Choosing a linear guide has to consider the following variables to conclude a
reliable static safety factor: average applied load on every slide, basic static
nominal load(C0) or basic permissible static moment(Mx、My、Mz). In case of
calculating life in a longterm consumed environment, it requires basic dynamic
nominal load(C) for an approximate result.
b. Basic static load rating (C0)
When a linear motion system in the static state or in motion is subject to an
extreme load or impact, a permanent deformation will occur between raceway
and rolling elements. If the deformation is excessive, the linear motion system can
not travel smoothly. Now, we define the basic static nominal load(C0) is a static
load of constant magnitude acting in one direction under which the sum of the
permanent deformations of rolling elements and raceway equals 0.0001 times the
diameter of the rolling elements.
c. Basic permissible static moment
When a linear guide gets a force that makes the balls distorted to 1/10,000 of
theirs diameter, we call the force as basic permissible static moment.
d. Static safety factor (fs)
The static safety factor indicates the ratio of Basic static nominal load(C0) to the
load acting on the linear motion system.
e. Nominal life (L)
The nominal life L is the total distance of travel reached without flaking by 90% of
a group of identical linear motion system that are operated independently under
the same condition.
f. Basic dynamic load rating(C)
When each of a group of identical linear motion system is applied independently
under the same condition, basic dynamic load rating C is the load of constant
magnitude acting in one direction that results in a nominal life of 50 km for a
system using balls.
12 Subsidiary factors:
a. Contact factor (fc)
In linear motion system, it is hard to obtain uniform load distribution in close
contact installation due to moments, errors on the mounting surfaces and other
factors. When two or more blocks in a rail are used in close contact, multiply basic
load ratings C and C0 by the contact factors shown below.
Number of blocks in close contact 
Contact factor 
2 
0.81 
3 
0.72 
4 
0.66 
5 
0.61 
Normal operation 
1 
b. Hardness factor (fh)
When working environment temperature exceeds 100 degrees Celsius, ft becomes
a key factor.
c. Temperature factor (ft)
When working environment temperature exceeds 100°C, ft becomes a key factor.
Remark:
When working environment temperature exceeds 80 degrees Celsius, the
material of seals and cages have to be able to endure the high temperature.
d. Load factor (ft)
Reciprocating motion usually occur vibrations, impacts and variable loads. In general, vibrations occur in highspeed operation, impacts due to repeated starting
and stopping and variable loads; therefore, it is difficult to calculate.
14 Friction resistance
Friction can be calculated by:
F = u * W + f
F : Friction resistance
W : Load
u : Coefficient of friction
f : Block seals resistance
II. APPLYING LINEAR GUIDE
1. Confirming conditions
It takes engineering calculation when adapting a linear guide system, and the
must knows are:
A. Composition: (distance between 2 blocks / rails number of blocks, number of
Rails.)
B. Mounting: (Horizontal, erect, on a slant, wall installation, or upside down
Mounting.)
C. Applied load
D. Frequency of use
A. Composition:
1. Distance between 2 blocks / rails: L0&L1 as shown.
L0: Distance of two blocks loaded on the same rail (mm)
L1: Distance between one rail to another (mm)
The distance of L0 and L1 matters the rigidity and life of the linear guide system
itself.
2. Number of blocks: in general cases, the more blocks used on a rail, the better the rigidity and the higher load capacity. However, layout plan and stroke have to be reconsidered.
b. Installation:
1.Horizontal Installation 
Horizontal Installation(W:load in direction of
compression) 
Erect Installation(W:load in direction of
compression) 

Slanting Installation(W:load in direction of
compression) 

Wall Installation(W:load in direction of
compression) 
c. Applied load
Load contains 3 elements: force, direction of load and object that is loaded.
 Force: Weight: it produces inertia when it moves.
Outer force: outer force comes from liquid pressure, air pressure and magnetic force. No inertia comes with it.  Direction of load: Can be divided into 3 dimensions.
Shown as Fx, Fy and Fz on fig.
 Position of load acts: Pfx, Pfy and Pfz are shown as fig, defined as distance from applied load to center of
driving power.
Driving power could be actuated by a ball screw, an oil pneumatic cylinder or a linear motor.  Distance between 2 carriages / rails: L0 & L1: as shown
 V/D figure:
Velocity (V): The highest speed
Distance (D): Distance that the system runs.
(D1): Distance moving from static to the highest speed
(D2): Distance at equivalent speed
(D3): Distance moving from the highest speed to static  Forces onto Carriages:
R1、R2、R3、R4 are forces from vertical directions
S1、S2、S3、S4 are forces from horizontal directions
d. Frequency of use:
Frequency of use has to be added into considerations when proving whether the engineering calculation fit the actual application.