Introduction to Industrial Automation

10.21   A Roller Conveyor System for Wrapping Plastic Membrane

Figure 10.21 shows part of a roller conveyor for transferring a plastic membrane from a produc-

tion machine to a wrapping machine. In this section of the conveyor, a floating folding is created 

deliberately, in order to have the potential difference between the rate of production and the rate of 

wrapping absorbed. The length of folding is measured with a laser-type photocell (PC) for distance 

measurement and should be kept between 40 cm and 50 cm limits through the regulation of the 

speed of the motor M

1

, which performs the wrapping. The analog output 0–10 V of the distance 

meter is stored in the memory location MW200 of a PLC. With the START and STOP buttons, 

both motors M

1

 and M

2

 of the roller conveyor start and stop, respectively. The operating speed of 

the M

1

 is regulated so that when:

Folding < 40 cm 



 Low speed

Folding > 50 cm 



 High speed

40 cm ≤ Folding ≤ 50 cm 



 Normal speed

In addition to the main programming task, tasks also include an additive digital output (not shown 

in the PLC) to be activated when the desired limits are violated, and write the overall PLC program.