July/August 2019

packed in a variety of food tray shapes and sizes without requiring any hardware modifications. Different types of food require different types of cutting. For example, chilled goods need a slower cutting speed than softer foods. Similarly, chopping orientations and angles for round products, such as pizza, are different from products baked in rectangular trays, such as flapjacks. The WMH cutting machine uses a pair of robot arms that perform all of the necessary cuts on the move and can match their speed to that of the line. The accurate slicing is achieved using state-of-the-art ultrasonic blades. These blades, supplied by Telsonic, can cut different materials quickly and accurately, applying very low pressures to the food. Compared to conventional blades, the amount of waste produced is much lower, especially when cutting near the edges of the material. And variable ingredients and toppings – such as cherries in cakes – are sliced without squeezing them or damaging the product, thus ensuring an aesthetically pleasing result. Fewer cuts The machine’s ultrasonic blades are 760mm long – the largest on the market. This results not only in shorter cycle times, but also higher quality. When slicing large trays of food, fewer cuts are needed on the same axis, minimising the risk of misalignment. The self-cleaning blades maintain a sharp edge, further streamlining the process. Telsonic worked with the automation supplier, Mitsubishi Electric, to optimise the coordination of the robots and the blades to ensure precision performance. As well as the two Melfa robot arms, Mitsubishi also supplied a Melsec Q series high- performance PLC, and matching components including HMIs and variable- speed drives. The PLC links the robots to a GOT2000 HMI, allowing operators to set the type of cutting required and to monitor the process. Particular attention was given during the design phase to establishing a reliable position-tracking system, which is key to ensuring that the robots cut the food correctly, without affecting the food trays or the conveyor belt. “Ultrasonic blades are extremely powerful, so we had to make sure they would cut through the product completely and stop before reaching the tray,” reports Mitsubishi’s sales manager, Steve Kirby. “Our solution can repeatedly position itself correctly with an accuracy of 20μm. Yet, we also had to minimise any upward or downward movement of the conveyor belt.”The conveyor belt therefore uses VSDs to regulate its horizontal motion while eliminating any height variation. Round and square One of the first customers for the new machine was Somerset-based Bakkavor Desserts – Highbridge, which was looking to replace an existing cutting system, that was nearing the end of its useful life, with a more modern approach that would allow it to cut both round products and rectangular tray bakes. Bakkavor visited WMH in Cornwall to see a demonstration of how the cutting machine would cope with its products – a mixture of rectangular tray bakes and round cheesecakes that needed to be slice at a rate of 10 pieces per minute. It was decided that a single-robot inline machine would be ideal for this application. From the early planning stages, Bakkavor, WMH and Mitsubishi discussed how to build an efficient, flexible machine that would also address the strict hygiene requirements of the food industry. Mitsubishi’s RV-F six-axis robots were felt to be ideal because they offer IP65 protection for food-grade washdowns, as well as “class- leading” speed and precision. While Bakkavor was waiting for its inline machine to be manufactured, it hired a standalone cutting cell fromWMH, allowing it to get into production immediately and to familiarise its operators with the user interface. n A ultrasonic blade cuts cleanly and quickly through one of Bakkavor’s cheesecake products .c o.uk r w.eplancoginee ww .er .cimat ehc Seor M.onimat otu Aeor LPE orM AN Se eingo M.de C ep FOOD PRODUCTION n