IAI America SSPA - Manual (Page 32)

3. Life
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3. Life
The mechanical life of the actuator is represented by that of the guide receiving the greatest moment load.
The “rated load” is one factor that relates to the traveling life.
There are two types of “rated load,” namely “static rated load” and “dynamic rated load.”
x “Static rated load”: Load which, when applied to a stationary actuator, leaves a minor pressure mark on
the contract surface.
x “Dynamic rated load”: Load which applies after a specified traveling distance under a load based on a
specific probability of survival at which the guide does not break
Guide manufacturers indicate the life of a guide using a dynamic rated load when the provability of survival after
50 km of traveling is 90%.
In the case of general industrial machinery, however, you should understand the specific life also for the purpose
of maintenance. Also, the life of a guide has a sufficient allowance relative to a radial load, and receives the
greatest impact by a moment load offset from the center of the guide.
With the IS series, the life is designed to ensure a traveling life of 10,000 km under a load corresponding to the
allowable load moment and at a load coefficient of 1.2 (safety factor).
[For the dynamic allowable load moment, refer to 2, “Specification”]
The calculation formula for allowable load moment at a traveling life of 10,000 km is shown below:
C
IA
: Allowable load moment
f
W
: Load coefficient (= 1.2)
M
50
: Dynamic rated moment when the probability of survival after 50
km of traveling is 50%
The life at the actual moment is calculated by the formula below:
L: Traveling live (probability of survival: 90%)
C
IA
: Allowable dynamic moment
P: Actual moment