Introduction to Industrial Automation

10.10   Modular Programming for a Set of Processing 

and Repairing Stations

A production line includes six processing stations and one repairing station, each one of which per-

forms its own process or assembly as the produced device passes through them. Each station operates 

according to its automation program P

i

 if this is called (executed) by the PLC. The sensor S

2

 detects 

possible defects of the produced device. In such a case, the device is forwarded to the repairing station 

that operates according to the program P

123

, while stations 1 to 6 stop operating. When the repairing 

procedure has finished and the repaired device is ready to reinsert in the central production line (some-

thing that is expressed by the activation of sensor S

4

), then the operation of stations 1, 2, and 3 must be 

bypassed. This means that only stations 4, 5, and 6 must start their operation or, in other words, the 

repaired device does not need processing in stations 1, 2, and 3. Sensor S

1

 signals the arrival of a device 

for processing and assembly. Sensor S

3

 signals the end of a device processing. The operation of the 

conveyor system is not examined here, as also it is considered that a new device does not come before 

the end of the previous device processing. It is ideal to develop a modular program for the stations’ 

operation, called organization block, including all sub-programs P

i

, i = 1–6 and P

123

 (Figure 10.10).

V

0

V

1

H

0

V

2

S

2

S

1

S

3

S

4

Tank no.1

Tank no.2

On

Off