Introduction to Industrial Automation

10.16   Stacking Machine of Light Objects

Suppose that a step motor is used in a stacking machine of light objects. The controller of the 

step motor has to save the number of objects that have already been stacked each time in its 

memory, in order to stack the next object. It is desired to develop such a controller for the 

motions in a PLC. Using the program written for the problem presented in Section 10.15, 

+24 V DC

+24 V DC

Driver

Step motor

b

1

b

2

RS

0 V

Step

Direction

Full–half step

Enable

I0.1

PLC

Inputs

Outputs

Q2.2

Q2.4

Q3.0

Q3.2

I0.2

I0.3

Figure 10.15  The step motor is controlled by the PLC through a driver.

---

Industrial Applications 

◾

 

395

write a complementary one so that the PLC accomplishes the sequence of the step motor 

motions shown in Figure 10.16 and specified as follows:

 

◾

With the first pressing of b

0

, the platform goes down 50 cm and returns to its upper location.

 

◾

With the second pressing of b

0

, the platform goes down 45 cm and returns to its upper 

location.

 

◾

With the third pressing of b

0

, the platform goes down 40 cm and returns to its upper location.

 

◾

With the tenth pressing of b

0

 the platform goes down 5 cm and returns to its upper location.

 

◾

With the eleventh pressing of b

0

 the platform, as in first pressing, goes down 50 cm and 

returns to its upper location.

Suppose that the rotation of motor axis by 1° causes a linear displacement of the platform of 1 mm. 

The b

0

 is an NO button connected to an additive input I1.0 (not shown) of the PLC, while the 

outputs are as shown in Figure 10.15.