Walkers Simulation Case Study

Simulation Modelling, undertaken by Coventry-based Production Modelling, has played a key role in both the successful delivery, and the on-going management, of an expanded warehouse and distribution facility for Walkers Snacks Foods.

A rapidly growing snack food market, and the ability to capture an increasing share of this market, in part thanks to some high profile marketing, has seen Walkers Snack Foods Ltd experience major business growth over the past few years. But, this success has also placed considerable new demands on its UK operations. To manage these, the company - which is now part of the global giant PepsiCo Inc - has undertaken a major programme of upgrading and expanding of production and distribution facilities. One of recently completed key projects in this programme, a vital element in the company's remodelling of its distribution capabilities, has delivered a massive warehouse expansion at Walkers' Leicester based factory and warehousing complex.

However, adding storage was only one of the requirements for this development. It also had to deliver operational process improvements in terms of picking efficiency and throughput, and so enable the output capacity of the whole Leicester complex to keep pace with requirements. Therefore, to help ensure that the final design solution was capable of meeting these demands, Walkers, and its project partner, the warehouse solution provider Swisslog, turned to simulation modelling, and the UK simulation specialists, Production Modelling. As it has turned out, not only did the modelling help prove the design concept, it provided detailed process analysis that led to direct project savings. Additionally, a detailed simulation model was also developed that is now being used by Walkers as an ongoing operational management and training tool.

Project Background

By the end of 2002, Walkers had identified that to keep pace with continued UK sales growth, the warehousing and distribution capacity at its Leicester complex needed to be radically increased.

At the time, the facility included two factories with seven production lines, two of which were recent additions, a single warehouse, fed automatically by the two factories, and the Southern Region Distribution Centre (SRDC). Sited side by side, the warehouse and the SRDC, had previously been integrated through the introduction of a monorail system. This runs on a circular track round the SRDC, transporting full pallets from the high bay warehouse to either the SDRC's marshalling lanes, for full pallet pick, or to the picking frames, and also transport case picks from the picking area to the marshalling lanes. But, with the increased production from the new lines, the storage capability of this facility, at 9800 pallets, was far from sufficient. In fact, Walkers was having to store products off-site and bring them back to the distribution facility for dispatch. Also, the maximum distribution throughput of the combined operation, at 200 pallets / hour, was also no longer adequate to effectively meet demand.

To solve these issues Walkers set up an engineering project team, and brought on board Swisslog, who would undertake the detailed design work and implement the solution. The concept design that this combined team developed was for a large second high bay warehouse, with space for 13320 pallets, which would be fully integrated with the existing warehouse and the SDRC.

This integration would be achieved by building the new warehouse on the opposite side of the SDRC, from the original warehouse, and then expanding the monorail system to serve both warehouses. The new warehouse, which would be directly linked to the factories, would then feed the monorail from the opposite site of the system to the existing feed, and so utilise the existing picking and dispatch capability and so create a combined operation that could deliver a significant increase in peak throughput, from 200 to 320 pallets / hour.

John Coates, project director for Walkers Snack Foods, explains, "We knew that we would get some important improvements by introducing a new warehouse on the site, and so reducing the need for outside storage, which was costly and inefficient. We also believed that the existing facilities, and in particular the monorail system, had latent distribution capacity that could be utilised to cost effectively deliver a major increase in combined throughput ."

However, while the principle was sound, and management approval for the investment was given the go-ahead, this concept was based on a number of system assumptions, and it was vital that these were fully addressed before detailed design and installation began. As Coates adds, "Significant questions remained as to whether the monorail would simply become too easily grid-locked in practice, when being fed from both sides, and what changes or additions would be needed in equipment, infrastructure, and operational practices to deliver the required throughput of goods."

To answer these questions the joint project team comprising of Walkers, IMI and Swisslog staff, brought in Production Modelling to undertake a detailed process modelling exercise.

Geraint Foulkes, the project manager for Swisslog notes, "Simulation Modelling is a tool that we have used on past projects. However, this was a particularly complex system and so it was important to find the right external partner for this work. In the end, the team looked closely at two suppliers, but we found that Production Modelling's understanding of the situation and complexities involved was far better, and they had the skills and experience to effectively deliver the detailed modelling that was required."

Simulation Strategy

The simulation work had a number of distinct phases. Initially, Production Modelling's team used the ProModel simulation software to model and verify specific elements of the system, at pallet level. In particular, close attention was paid to the configuration of the monorail system.

This model was not only able to answer the key question, that the system could be used as anticipated without any major configuration changes, but also provided important data for the overall project that would have only been found by expensive trial and error. For a start, it had been anticipated that to provide the 320 pallet / hr throughput, up to six more monorail trolleys could be needed. But, the simulation was able to prove that there were already enough trolleys on the existing system to meet this peak demand, which meant a direct project saving of up to £150 000.

Another of the major contributions of the initial simulation exercise was to determine that during the part of the week when the system was not being run at peak throughput, but at a much slower rate of 160 pallets / hr, it was important to park a number of unused trolleys in a new parking area. The empty trolleys when rotated with full ones, jammed the system.

As Coates adds "Overall, the decision to apply simulation technology, and the expertise of Production Modelling, has proved to be a key aspect in the successful delivery of this project."