The latest bespoke cheese cutting machine from Northwood Food Machinery of Stoke-on-Trent provides precision portioning of blocks of cheese that weigh up to 85-kg. This has drastically cut the time for the task and gives accurate and repeatable results every time. The control and accuracy of movement of the blocks of cheese through the machine is attributed to the choice of Commander SK AC drives from Control Techniques.

The machine is now installed in Dijon at Tippagral S.A., a leading supplier of cheeses for the wholesale and food manufacturing markets in France and central Europe.

"We were faced with the task of stopping these huge blocks of cheese instantly," says Northwood Food Machinery director Mike Southwick, "A lack of friction in the gearboxes meant the blocks were over-running the target position by some 100-mm. We brought in Control Techniques, who were confident that they could give the degree of position control required, using the smallest of their general industrial drives, the Commander SK. On the first trial, these drives stopped the motors on target - and without any additional cost of braking resistors!"

The machine is divided into four conveyor sections, each driven by a 0.37-kW Commander SK AC drive. The incoming conveyor's role is to ensure a fixed pitch between the cheeses as they move through the machine.

The second conveyor section moves the cheese into the machine and, when the way is clear, on into the third section. This conveyor has optical sensors that feed back to the controlling PLC which initiates a rapid stop exactly between two pneumatically controlled 'pusher-plates'. This is to ensure that the cheese is absolutely central on the conveyor.

After being centralised, the cheese is moved by the next Commander SK on to the lift section of the conveyor and is stopped at the required position. It is then elevated by scissor-lift to in front of the cutter section, where a heavy duty pneumatic ram pushes the cheese through the 'grill' of cutting blades, and a guillotine at the reverse side cuts the cheese to the required length.

Director of Tippagral SA, Neil McAuley, explains, "We portion some 7,000 tonnes of cheese per year, mainly Emmental, but also Cheddar, Gouda, Edam and Mozzarella. Some 75% of our throughput is grated, but many customers, particularly wholesalers and manufacturers of pizza and sandwich / baguette producers, require the cheese to be cut into specific sizes and shapes, e.g. 9x9-cm, 7.2x7-cm and 12x5-cm. This machine will dramatically streamline this aspect of our operation and cut our labour costs."

This order follows the success of a similar machine in use at parent company, the Tipperary Co-op in Ireland.

Commander SK is a high specification, general purpose AC drive, packed with features in a compact size that takes up little room in a cubicle. Featuring integral dynamic braking as standard, the drive has the ability to absorb the energy created by fast stops, as in this case, whilst giving very smooth, precise control of off-the-shelf motors. The drives on this cheese cutting machine are hard-wired into the PLC controller to give a fast digital link and are simply programmed to give smooth acceleration and instant STOP, when they individually receive instructions to do so.

"We are delighted with the results," says Mike Southwick, "the Commander SK drives have exceeded our expectations. "We simply could not have achieved these results with any other drive - and we're very pleased with the support we've received from Control Techniques, who helped us set it up and provided us with the programming."