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Rockwell Automation speeds Crunchie line at Cadbury
RSView32 allows the whole process to be monitored from one central control room
Since 1929 Cadbury's Crunchie has been one of the top selling chocolate bars in the UK. Although the plant used for producing the Crunchie bar is modern, the existing distributed control system (DCS) that was installed in 1981 was becoming a problem and so Cadbury looked for a replacement.
The critical time scales and scope of the project presented a challenge for the Cadbury project team, Rockwell Automation and Aston Dane, a Rockwell Automation solution provider. Cadbury could not afford to let consumers switch to a competitor's product while old equipment was being removed and the new control system was being installed. Rockwell Automation, through its Allen-Bradley and Rockwell Software products and support, was the partner Cadbury needed.
David Williams, a systems engineer at Cadbury, said, "Whilst the Ferranti
ARGUS DCS had served us well for a number of years, we were starting to have problems with support against a background of increasing downtime and pressure to continue to enhance the automation of the process. Added to this, Ferranti had gone out of business and we had concerns over year 2000 compatibility. Something needed to be done quickly."
The original Ferranti system had taken 2 years to install and commission and cost £2m. Today's demand for Crunchie bars gave Cadbury's management no choice but to stipulate a very tight schedule for the project of 10 weeks with a budget of £890,000
The scale of the task was daunting with over 3000 I/0 to be replaced. The original software had taken 10 man-years to develop and a further five man-years had been spent on testing. Added to this, the system had over 1000 control devices and a menu of around 100 different operator screens. The system was complex and there was a lack of knowledge, which slowed maintenance and repair, as well as inhibiting development.
The new system is based around four Allen-Bradley PLC5/80C ControlNet programmable controllers. Installed within the same panels, and connected via ControlNet, is the Allen-Bradley 1771 range of I/O. Although the new system was considerably rationalised, there are still over 2500 I/O points. The 1771 range provides signal interfaces to suit AC and DC applications, with a wide range of signal levels including standard analogue inputs and outputs.
Ethernet and DeviceNet communication modules communicate to the various other devices. Ethernet provides backbone communications between the PLCs and PCs running Rockwell Software RSView32 HMI software.
The system also runs Rockwell Software RSTune, a Windows based software package that optimises PID control loops. Using RSTune, Cadbury is able to analyse, simulate, document and download optimal tuning parameters.
There are 24 Allen-Bradley 1305 drives located in the electrical panels and connected to the PLC's using DeviceNet. The Drives range from 0.37 to 7.5 kW, providing reliable and flexible speed control of motors positioned around the plant.
With the help of RSView32, the whole Crunchie process is monitored and controlled from a central control room. Two operators work the plant 24hrs a day and are able to monitor the process using RSView32 to show the status of individual stations around the plant. There are also CCTV's positioned at critical points to give immediate warning of manufacturing problems.
David Williams is very pleased with the way the project was implemented. "We started to plan in January although the changeover was not scheduled until November. We were able to use this time to build up stocks of finished product and prepare for the changeover. This included identifying all of the existing cabling and devices and preparing 5,000 cables in looms ready for installation. We were able to save time by running many tasks in parallel - for example software specification, development and testing. Another benefit provided by RSView32 was the ability to simulate the production process using software and this was used to train the operators before we went live."
The new system required over 4 tonnes of cable and there were 2,500 I/O points to be wired. On the system side there were 200 operator screens to be configured and 20,000 lines of software to be written - the equivalent of 4 man-years of work.
While the plant was being re-commissioned, the production and packaging shifts had to be re-deployed to other plants in the factory. In the event, the plant was manufacturing product after only 4 weeks - well within the revised target of 6 weeks. Such was the success of the changeover that the running efficiencies that Cadbury were experiencing with the old system were soon exceeded and many long-standing problems were quickly resolved. Not only were the time schedules met, the project was completed well within the budget and without any safety incidents.
David Williams concludes, "Rockwell Automation is able to supply a wide range of industrial control products as well as software systems and this total package made a considerable contribution to the success of this project. The changeover was not without its problems and we challenged Rockwell Automation's expertise and support on a number of occasions. Some of the questions we raised were complex but they always responded with someone in their organisation who could provide an answer. We are continuing to enjoy the benefits of increased production and enhanced reliability provided by the new control system."
RSView32 customer testimonials
Rockwell Automation, through its Allen-Bradley and Rockwell Software products and support, was the partner Cadbury needed to produce its Crunchie bars.
Rockwell Software RSView32 HMI software, a scalable HMI solution and part of our View Anyware platform, is used by Cadbury in the UK to monitor its Crunchie production line.
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