Introduction to Industrial Automation

between in-stroke and out-stroke applied force of a double-acting cylinder (b).

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Elements of Electro-Pneumatic Components 

◾

 

167

 

Double-acting cylinders:

F

AP F

Out st

real

friction

=

−

(

rroke force

or

F

A P F

In stroke force

real

friction

)

(

)

= ′ −

where A is the area of the piston from the left side and A

′

 is the useful surface area from the right 

side, as indicated in Figure 5.8b, with the following definitions: A = 

π

D

2

/4 and A

′

 = 

π

(D

2

−d

2

)/4.

5.6.1   Length of Piston Stroke

For a fixed diameter of a pneumatic cylinder, the length of the piston’s stroke cannot be as long 

as we want. This is because a large length of stroke will create a large mechanical fatigue on the 

piston’s rod, through which the force is applied on the load (F

real

). To avoid this fatigue when it is 

desirable to have a greater stroke, we should select a bigger diameter for the cylinder, and conse-

quently a bigger diameter for the rod. With the utilization of a corresponding nomogram, as in the 

previous case of a pipe diameter calculation, the allowable stroke with respect to the rod diameter 

and the applied force can be calculated.