- February 04, 2012
- Case Study
Automation.com, February 2012
Barbers Farmhouse Cheesemakers in the UK uses Rockwell Automation‚Äôs ControlLogix PAC and 3D laser scanners to control an Arcall C52 cheese cutter. Another PAC controls a suite of conveyors driven by servo motors. All communications are via EtherNet/IP.
Barbers Farmhouse Cheesemakers, based in Somerset, UK, relies very much on its traditional recipes to maintain its position as one of the U.K.'s leading dairy product manufacturers. Like all manufacturers, it is extremely conscious of waste and what the industry calls ‘giveaway’ – over-sized portions. With giveaway levels running at between four and five percent on its existing portioning line, it decided to seek a more efficient solution, especially in light of its capability to process more than 14 tonnes of cheese in a single day. Challenge When it comes to food portion weights, manufacturers are allowed a certain amount of leeway. The average weight of a batch must be greater than the stated fixed pack weight and only a certain amount of portions are allowed below this weight – known as the T1 and T2 points. Portion size must be controlled very tightly, not only to meet legislative demands, but also, from a financial perspective, to create portions that are not too heavy – with any oversize being labelled giveaway. The economics are simple. If you are creating 250g portions and you are 2g overweight each time; then you are "giving away" one portion in every 125. With Barbers processing up to 14 tonnes of cheese per day, a 2g give away level per portion is significant. It is for this reason that Barbers called upon the services of Machine Builder, Arcall, and by working with Rockwell Automation and its distributor Routeco, Arcall was able to build a machine that based its primary operating performance around less than 1 percent giveaway. Solution The strength of the Arcall C52 cheese cutter lies in its ability to analyse the blocks of cheese and then determine the most efficient means of positioning them using extremely precise process and axis control. The first step involves weighing the 20kg blocks to determine the optimum cut positions in order to create eight smaller 2.5kg blocks. It does this using three vertical cheese wires and an adjustable horizontal wire positioned to create an optimum cut line. Once cut, the upper and lower layers are separated and the top layer is flipped over. Each of the 2.5kg blocks is then separated and passed under two 3D laser scanners, which feed point-cloud data – accurate to 0.2mm – into an Allen-Bradley ControlLogix Programmable Automation Controller (PAC). The PAC then determines the optimum way of cutting the cheese into the individual portions. This is achieved using two vertical cutting blades, which are positioned using heavy duty, high-speed Allen-Bradley linear motors (in preference to a pneumatic solution). The cutters can also be angled – with the whole assembly pivoting – to create cheese wedges. The automation components for the machine were sourced through Routeco. Jeff Bell, Account Manager at Routeco explains: "This is a key account for us and we knew that if we offered the right support we would have a really positive outcome. Rockwell Automation invested significant engineering resources into this project, employing one of its European GOTCs (Global OEM Technical Consultants) for two weeks on site at Arcall's facility, helping the engineers to create this "first of its kind" machine." GOTCs are often at the forefront of Rockwell Automation projects. As specialists in their sector they bring a wealth of experience and knowledge to all of the projects they work on. As well as improving the technical relationship with the customer, they also act as a focal point for the project, coordinating information and technical capabilities. The entire line, based on Rockwell Automation Integrated Architecture utilises several Allen-Bradley® devices and components. They include a ControlLogix PAC with a 16-axis motion card to control a suite of conveyors driven by Kinetix servo motors. The conveyor and cutter speeds are very carefully matched to help deliver the best possible accuracy. All communications are via EtherNet/IP with the operators employing PanelView Plus HMI to oversee the machine. Components include isolators, circuit breakers, contactors, power supplies, push button and E stops. Result "Rockwell Automation has been incredibly supportive," explains David Woollard, Commercial Director and owner of Arcall. "It was a reasonably complicated set up, so we were delighted when they lent us a test rig prior to machine build. We built this machine for Barbers on the basis of a 'guaranteed less than 1 percent giveaway' and so far it is easily achieving this. We have been able to programme the PAC so that if the average begins to creep in either direction, it will compensate to address the giveaway and T1 and T2 figures. "One of the other key strengths of the Rockwell Automation system is its ability to synchronise all the axes," Woollard continues. "The belts and pushers have to work in harmony so we do not generate any undue stresses in the machine and, more importantly in this instance, so we don't compress the cheese, creating ambiguous weight/volume changes. It also 'talks' openly with the weighing and scanning hardware on the line. "With many supermarkets preferring to sell fixed weights rather than random sizes, the ability for their suppliers to provide portioning accuracy is vital from both an economic and legislative point of view." Woollard explains. "With 14 tonnes of cheese passing through this plant – a 5 percent giveaway equates to as much as 700kg – or 2,600 extra 270g portions in a single shift, which could be worth between £1,400 to £3,000 per day depending upon whether Mild or two year old Extra Mature." The machine was installed to replace an older unit to extend its product offering above its oiler and sprayer units used by many of the world's leading food manufacturers. Arcall has also signed a contract with Barbers to replace a second machine and order prospects from other companies are looking extremely promising. Arcall is a long standing Rockwell Automation OEM Partner, standardising on Rockwell Automation. "We have been using Allen-Bradley equipment for a while now, ever since our first export to the USA in 1988." Woollard explains: "Our machines see action in over 60 countries, so we have to be confident that our automation suppliers can offer worldwide support and spares. Rockwell Automation is now our preferred vendor for both hardware and software and 10 percent of our entire workforce is trained on Rockwell software."
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