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For years, pallet loading has been at the back of the queue for investment in automation. Although primary packaging line speeds are pretty quick - particularly in industries such as confectionery where break-neck speeds of 600 packs per minute are not uncommon - by the time products get to the case packing or palletising stage, line speeds have dropped to the point where it's not always that much slower to carry out these tasks manually.

However, this situation could be changing.

“We’re seeing a lot of people investing in palletising – it’s the one part of the line that they haven’t focused on so much,” says Mike Lindsay, sales manager for Integrapak, which distributes Italian-built Apsol palletisers in the UK.

This view is backed by Tony Dowling, robot sales specialist with Kuka Automation and Robotics, who says: “I am seeing an increasing number of companies moving to palletising. It seems to be mainly for health and safety reasons or because they are struggling to find people who are prepared to do heavy lifting day in day out.” There were 858 robots used for palletising in the UK by the end of 2006, according to the International Federation of Robotics. Of these, 48 were installed in 2006. Mike Wilson, president of the British Automation and Robotics Association, estimates the current number to be around 1,100.

For Ocme UK, a robot integrator and manufacturer of conventional palletisers, sales are split fairly evenly between conventional four-axis layer palletisers or six-axis robotic palletisers. Ocme’s Steve Wyard says: “The choice very much depends on the application. Robots come into their own when the requirement is to palletise from more than one production line, or the application requires a lot of flexibility. A modern robot can palletise up to four or five production lines simultaneously.”

Bottling it
Ocme has installed robots with special gripper heads for palletising loose bottles and multipacks onto display pallets.

“This application requires a great deal of flexibility,” says Wyard. “The robot often needs to handle a range of products, from loose bottles to multipacks and normal packs, a variety of pallet sizes and different types of interlayers. It is difficult to get such flexibility on a conventional palletiser.”

OPM Samas, whose palletisers are available in the UK from Hansel UK, agrees that where flexibility is key, robotic palletisers are king. “In our sector, food, very few customers choose non-robotic solutions, since this market requires regular changes to product packaging and size,” says an OPM spokesperson. “It is easy to adapt a robotic palletiser; they have software capable of creating alternative pallet layouts and uploading them automatically to the palletiser.”

Another obvious but important advantage of robots is size. “Layer palletisers are big metal boxes with conveyors running in and out. Robots don’t take up much space,” says Dowling.

One of the fastest-growing applications is loading mixed pallets as a result of retailer demands for products to be configured to suit them – and it’s a trend that plays right into the hands of robots.

“The use of robots for mixed palletising will increase significantly in the next few years,” predicts Frank-Peter Kirgis, head of sales, robotics, at ABB. “This is mainly due to retailer demand for pallets to order. Stores in the countryside have reduced space for storage and goods have to be delivered to specific needs.”

Options for loading mixed pallets are still fairly limited. Kuka has developed a patented gripper that can pick up complete layers of what it calls ‘rainbow pallets’, where each layer is different, as long as the product within each layer is the same.

“We’re also developing something that will be capable of dealing with different sizes and weights. There’s a lot of development in that area,” says Dowling.

But if flexibility is the robot’s forté, productivity is its weakness. On high-speed, dedicated lines, such as canning or bottling lines, a robotic palletiser is no match for a layer palletiser.

Ocme’s Orion HM2 inline palletiser, for example, can handle up to 10 layers a minute, which can equate to a production speed of more than 150 packs per minute.

Layer machines also tend to produce a better stack, because of the mechanical devices, which single-column robots lack, that are used to square layers, according to Golconda, which sells Italian-built Concetti sack palletisers in the UK.

While designers of robotic palletisers can’t do a great deal to improve the neatness of the stack, they have been busy working on productivity. OPM Samas, for example, has just delivered two robotic palletisers, which will pick up 50 boxes per minute in a restricted space, to an Italian customer.

Ocme has also made progress on speed. “Modern robots can handle a payload in excess of 500kg,” says Wyard. “This lets us manufacture quite complex heads. We have installed robot palletisers with gripper heads that can pick up a complete layer of product.” For example, on a bottling line, a complete layer of two-litre PET bottles on a 1,200x1,000 pallet weighing 250kg can be palletised at a rate of up to six layers per minute. Such systems come very close to the high speeds that have to date only been achievable using conventional palletisers.

The best of both
In sack palletising, some of the issues that have traditionally plagued case palletising robots have been overcome with hybrid systems. Chronos Richardson, a supplier of both traditional and robot palletisers for bags filled with loose materials such as flour, grain and compost, has pioneered a hybrid palletiser called the Chrono-Pal Compact Palletiser. This is said to incorporate the best features of both types of palletiser, such as the layer forming/side compression features of high-level palletisers and the innovative bag gripper designs of robot palletisers.

The Chronos bag gripper operates automatically to turn bags through 180° or 90° before depositing the bag on the pallet. Chronos says it has increased the sophistication of the gripper even further, enabling it to pick up and palletise either individual or multipacks – even different pack sizes.

“The programming logic used actually ‘learns’ from each palletising operation and optimises its own speed for future pallets,” says Steve Allman, the company’s UK sales engineer.

Italian firm Concetti manufactures a combination unit called the PS-3A. This uses a robotic gripper tool, which enables poorly filled bags to be handled and sewn-top bags to be overlapped - both significant advantages over layer palletisers. The gripper tool rotates through 360° and is driven along the x and y axes by servo motors and a system of toothed belts.

The layer is built up on a stripper plate with side compression to confirm the layer before it is deposited on the stack. After the layer depositing phase, the stripper plates apply top compression to the stack to ensure a level base for subsequent layers.

Golconda claims the PS-3A is ideal for products that are aerated or bags that are irregular or need to be overlapped, and can operate at up to 1,200 bags per hour.

Offering flexibility and a small footprint, robotic palletisers are catching up, and in some cases, combining with layer palletisers. It remains to be seen if they will take over altogther.

FAREWELL TO FORKLIFTS?

If you saw an unmanned vehicle driving down the street, you’d probably panic. But no-one would bat an eyelid on the warehouse floor.

There are around 500 laser-guided vehicles (LGVs) in warehouse and production locations around the UK. According to Aetna, they are becoming an increasingly common sight as a replacement for conventional forklift trucks.

They can be programmed to pick up loaded pallets from the end of a line and deposit them in a chosen location.

“They are very useful for reducing the need for conveyors in the warehouse or processing area,” says John Hawkins of Aetna UK, which distributes the Euroimpianti range of LGVs in the UK. “Where there are several production lines that need to feed into one stretch wrapper, for instance, the traditional method would be to install long runs of roller conveyor, which would result in reduced access to other parts of the line. Using the LGV, the factory floor is completely open for normal traffic.”

LGVs are particularly suited to moving unstable loads as they will pick and place pallets carefully and travel between stations at the optimum speed, which can include slowing down over rough or pedestrian areas, according to Aetna.

Safety is aided by the use of scanning sensors as well as bump stops to detect any objects left in the LGV’s path.

One of the latest ideas Euroimpianti has been working on is loading pallets onto lorries without an operator – this was demonstrated at Interpack.