PLC Programming Practice-Road roller assembly line

Road roller
Scope of work – Assembly of road roller.
An assembly line includes fitting of engine on chassis, fitment of axles, mounting of body, and fitment of wheels and rollers. Conveyor is driven by an electric motor coupled with a gearbox. An electric brake is also connected to the motor that ensures braking of the electric motor.

Assembly line of road roller

Assembly line of road roller

Input and Output devices list

Input devices Output devices
Start PB (X00) Conveyor forward command (Y00)
Stop PB (X01) Station 1 hold lamp (Y01)
Emergency PB (X02) Station 2 hold lamp (Y02)
Station-1 Pause PB (X03) Station 3 hold lamp (Y03)
Station-2 Pause PB (X04) Station 4 hold lamp (Y04)
Station-3 Pause PB (X05) Station 5 hold lamp (Y05)
Station-4 Pause PB (X06) Conveyor motor brake (Y06)
Station-5 Pause PB (X07) Conveyor stop command (Y07)

Hardware and software details
PLC – FX 3U 30 M
HMI- MELSEC
PLC & HMI communicatio n- Ethernet
PLC Programming software – Works2

Operation

● When a start PB is pressed, a motor brake will be released first and after 1 sec the conveyor forward command will be given to the VFD.
● A conveyor will move in forward direction with 2 mm/1 sec speed.
● Assembly of components is done during forward movement of the conveyor. In case an operator requires more time, he can pause the conveyor and finish his work, and release the pause button so that the conveyor will start again. All 5 stations have been provided with a pause button.
● When a stop PB is pressed, the conveyor will be stopped and after 1 sec a brake will be applied.

Programming using works 2 software

● Program is written as follows. When a start press button is pressed, the memory bit gets latched.
● If one of the pause buttons is pressed, it will unlatch the start command.
● Once the start command is received, it will release the brake first and switch one the motor after 1 sec.
Programming using works 2 software
● If one of the push buttons is pressed, it latch the stop command bit first.
Programming using works 2 software
● Once the stop command bit gets latched, it will stop the motor first and then apply brake after 1 sec.
Programming using works 2 software
Programming using works 2 software
● Pause button glows the lamp as shown.

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