Nominal Life

Static Safety Factor

The basic static load rating C₀ refers to the static load with constant direction and magnitude, under which the calculated contact stress in the center of the contact area between the roller and the raceway under the maximum load is 4000 MPa. (If the contact stress exceeds this level, it will affect the rotation.) This value is indicated as "C₀" in the dimensional tables. When a load is statically or dynamically applied, it is necessary to consider the static safety factor as shown below.

f_S	Static safety factor in relation to C₀ (see Table1 )
C₀	Basic static load rating (kN)
P₀	Radial load (kN)

The permissible load (F₀) indicates the permissible value of the applied load determined by the strength of the stud section of the Cam Follower. Therefore, it is necessary to consider the static safety factor f_M against F₀ as well as f_S .

f_M	Static safety factor in relation to F₀ (see Table1 )
F₀	Permissible load (kN)
P₀	Radial load (kN)

* The minimum value for the static safety factor is based on the presumption of appropriate lubrication and optimal conditions for mounting and assembly. It is not possible to calculate the effect on internal loads that may be caused by improper mounting, deformation of mounting components, or the like. Please take all necessary action to ensure safety.

Table1 Static Safety Factor (f_S , f_M )

Load conditions	Lower limit of f_S and f_M
Normal load	1 to 2
Impact load	2 to 3

Calculating the Nominal Life

The nominal life (L₁₀) is obtained from the following formula using the basic dynamic load rating (C) and the load applied to the cam follower (P_C ).

L₁₀	Nominal life (rev.)
C	Basic dynamic load rating * (kN)
P_C	Radial load (kN)

Calculating the Modifi ed Nominal Life

During use, a cam follower may be subjected to vibrations and shocks as well as fluctuating loads, which are difficult to detect. In addition, the operating temperature will have a decisive impact on the service life. Taking these factors into account, the modified nominal life (L_10m) can be calculated according to the following formula (2).

Modifi ed factor α

α	Modified factor
f_T	Temperature factor (see Fig.1 )
f_W	Load factor (see Table2 )

Modified nominal life L_10m

L_10m	Modified nominal life (rev.)
C	Basic dynamic load rating * (kN)
P_C	Radial load (kN)

* The basic dynamic load rating (C) of the cam follower shows the radial load under which the nominal life is 1 million revolutions when a group of identical cam follower units independently operate, assuming a constant direction and magnitude of the load. This value is indicated in the specification tables.

Calculating the Service Life Time

When the nominal life (L₁₀) has been obtained, the service life time (L_h) is obtained from the following equation.

For Linear Motion

L_h	Service life time (h)
L	Nominal life
D	Bearing outer diameter (mm)
ℓ_S	Stroke length (mm)
n₁	Number of reciprocations per minute (min^-1)

Note) The normal service temperature is 80℃ or below. If the product is to be used at a higher temperature, contact THK.

For Rotary Motion

D₁	Outer ring contact average diameter of the cam (mm)
n	Revolutions per minute of the cam (min^-1)

Table2 Load Factor (f_W )

Condition	f_W
Smooth motion without impact	1 to 1.2
Normal motion	1.2 to 1.5
Motion with severe impact	1.5 to 3