PLC upgrade increases uptime, speed and line responsiveness

04 July 2021

An automation solutions provider, Control Freaks, applied innovative PLC technology to solve production challenges and increase competitiveness at a pizza production facility. 

Bakkavor’s Holbeach St. Marks pizza production facility features a large fully automated manufacturing line that extends over two floors, to turn raw materials into finished products. The basic process mixes mainly flour and water to make pizza dough which then continues to be rolled, stretched, heat treated and proved. Once the dough is ready, round pizza bases are produced.

Each single process builds on the steps before it, so any issue upstream in the sequence may influence the end result and is also difficult to correct downstream. In such a highly synchronised system, effective inter-process control is crucial. 

When a project was started to make improvements to the system, the existing control system on the dough rolling section was over 20 years old. Simply as a result of its age and relative obsolescence issues had become ever harder to fix and so production was not running at optimum efficiency.

Reverse engineering 
When looking at migrating the existing control system to a new, modern setup, Control Freaks, working with Mitsubishi Electric, noted the presence of some programming code operating on a separate processor, or microcomputer, within the original PLC set-up. The 16-bit processor was not able to handle complex mathematical functions, therefore between 30-50% of the entire dough rolling process was handled by this separate microcomputer.

To further complicate the upgrade project, there was no way to extract this code to include it in the new control system. This made it necessary to conduct extensive reverse engineering to identify what functions were controlled by the microcomputer, how they played a role in governing the process and then to re-write this code in the new infrastructure. David Hamilton, site engineering manager for Bakkavor Pizza, explains: "Not only were there no diagrams to help the engineers understand what the code was controlling, but no member of the staff could help, as the engineers who worked on the initial setup has long since retired."

Clint Johnson, director at Control Freaks, said: "The absence of any documentation on the existing code within the control system made the reverse engineering operations particularly challenging. Mitsubishi Electric's specialised teams provided support, conducting crucial investigations. Their help was key to the successful completion of the project. This level of assistance provided is one of the many reasons why we are proud Mitsubishi Electric partners."

The next step of the project was to replace the old PLCs with new Mitsubishi Electric Q series controllers which was equipped with integrated Ethernet-based network communications, enabling them to be easily connected to inverters and other pieces of equipment.

In addition, the two automation specialists replaced the existing third party stand-alone I/O components using the CC-Link IE Field Basic network system which is integrated within the new PLC modules. This has allow Bakkavor Pizza to save panel space which will be used to host the new system's inverters and servos.

Following installation of the new system, Bakkavor Pizza noticed increases in the uptime, speed and responsiveness of the bakery line, as well as higher product quality and consistency. David Hamilton concludes: "The benefits of this new, automated control system were immediately noticeable. Not only did it manage to address the challenges we were facing but it exceeded our expectations."

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