Cadbury's have standardised on the Allen Bradley range of PLC's and
PanelView Local Operator Interfaces and this project was no exception.
In addition, Cadburys were keen to realise the "cost/time" benefits of
the modular process control system design and associated application
software previously developed with Aston Dane plc and apply it to the
ingredients handling and chocolate tempering areas of the process.
Monitoring and control of the main process was achieved via a PLC
5/40 for the Centre Ingredients area, a PLC 5/20 for the Enrobed
Chocolate area, plus two No.PanelView Operator Interface Panels.
Connection from the centre ingredients PLC to the weigh belt feeders
for the communication of set point and status information was carried
out via a Modbus interface connected through an Allen Bradley Basic
module. The two PLC5's communicated common information via a DH+
network.
The Enrober and Forming belt system were controlled by third party
supplied Allen Bradley SLC 5/03's. To ensure that the main
process control system is aware of the status of this equipment the
two SLC's were connected via a DH 485 network to the main DH+ network.
The Wrapping and Packaging Area consisted of a number of standalone
wrapping machines fed via a common conveying system. Control of
this conveying system was carried out via a standalone SLC 5/03 with a
limited interface to the main process control system via hardwired
signals for important process interlocks.
Close Co-operation
The project was successfully designed and built within a very tight
window of opportunity and within budget. All testimony to
the good planning and project management aided by the modularised
approach developed over many years of close co-operation between
Cadbury's and Aston Dane.
