Pneumatics help to cut the cheese

A novel, high-speed ultrasonic cheese-cutting machine relies on pneumatics technology to cut portions of cheese consistently – within 1% of weight tolerance. New Zealand-based Ryan Manufacturing (RML), which makes automated packaging and process machinery, has developed the 3350 ultrasonic cheese cutting machine. It can cut 300 slabs of cheese per minute – around 200 per minute faster than competing machines, it claims. Most cheese cutting machines use conventional steel wire cutting equipment. RML’s patented design uses ultrasonics to help the blade to cut with high speed and accuracy. Starting with 20kg blocks of cheese, it can cut 250g, 500g, 750g and 1,000g portions. A range of other sizes can also be selected. Danny Ryan, managing director at RML and inventor of the machine, explains: “This enables us to cut portions of cheese at rates of up to 300 per minute, with a weight variation of less than 1%.” Motion and control systems are key to the machine’s operation. For this, RML selected pneumatics equipment from Norgren. As Ryan puts it: “We have had excellent experiences using Norgren pneumatics.” Pneumatic actuators power the various mechanical operations on the machine. During the machine cycle, blocks of cheese need to be rotated through 90[degrees]. This mechanism is driven by a Norgren RA/8000 ISO/VDMA series, double acting cylinder fitted with the optional piston rod locking control. According to Ryan, this was chosen to ensure that there is no movement in the event of an emergency. Norgren’s rack-and-pinion rotary cylinder, RA/162000, is used to control the 180[degree] rotation of blocks of cheese up to 10kg in weight. Built-in double cushioning ensures a smooth operation and fine-tuning of the rotation angle can be achieved using the ends-of-stroke adjustment screws. For vertical lifting and horizontal transfer operations, Norgren’s M/46000 rodless pneumatic cylinders provide a neat, compact installation. These cylinders, and all other actuators on the machine, are controlled from Norgren’s V22 series valve island with Multipole connector. The pre-assembled, pre-wired construction enables straightforward installation and a central focus, for easier set up and diagnosis. For operator safety, the 3350 also has a comprehensive, interlocked guarding system. A Norgren Excelon P74 soft start/dump valve brings the machine gently to life when it is first switched on. As an extra safeguard, the built-in manual lock out slide overrides the normal start and dump signal to dump air immediately. Formed in 1981, RML employs around 50 staff at its Te Rapa factory in New Zealand. With most of its machinery aimed at the food and beverage industry, the company also manufactures machines that fold cartons for the kiwi fruit industry and for placing mussels and cheese into boxes. Around 2000, Danny Ryan – in conjunction with New Zealand Milk Products and Ziming Qi, a student at the University of Waikato – developed the first ultrasonic cheese cutter. Conveyor belts move blocks of cheese through a 13m x 2m machine, where they are cut into rectangles. They are then mechanically pushed through a more traditional wire type cutter, slicing them into blocks of the required size. The usual problem cutting cheese is the varying block sizes, which supermarkets require. Cheese is stored to cure before it is cut and the blocks actually change shape, since those on the bottom of the pile bear the weight of those on top. This problem is dealt with more easily and effectively with RML’s ultrasonic machine, as the ultrasonic ‘horns’ can be adjusted easily to cater for these different dimensions. Ryan says: “Most other methods use wires that the cheese is pushed through. They are not easily adjusted and it is very labour-intensive. The quality of the cut is also reduced and there is wear and tear on the blades as they are in contact with the cheese. The ultrasonic ‘horns’ do not come into contact with the cheese.”