An automated system based on a Motoman SP100X 160kg payload  4 axis Palletising robot for stacking of cardboard cases of food products has replaced the arduous job of lifting cases by hand at the Wednesbury factory of Red Mill Snack Foods in the West Midlands.  Costing £200,000 including conveyors and handling equipment supplied by Soco System (UK) Ltd, the system has eliminated the need to employ up to three operators per shift, 24 hours a day from Monday to Friday.  According to Red Mills' manufacturing director, Simon Faithfull, payback has been calculated at less than 22 months.

Five bagging machines/production lines are served by the new system, which went live in August 2005.  On the day that the company was visited, three individual lines were processing Salt and Vinegar Twirls, one was devoted to Tortilla Chips and the other was idle.  Bagged product from the production machines is packed manually, 24 packets per case for Twirls, following which the case is top and bottom taped automatically before it continues its journey.

Actuated in response to instructions from a host computer, a series of sensors detects the presence and identity of each case, allowing timed pusher cylinders to orientate as necessary and count them onto a layer forming

table.  Each product variety has its unique layer pattern programmed into the computer; for Twirls it comprises 13 cases – two rows of five and three rotated through 90 degrees placed at the end.

Once the complete layer is formed, the robot picks it up in a specially designed gripper and transfers it to one of five available palletising positions (either Chep or Euro pallets) that are situated on pallet roller conveyor sections located next to a shrink-wrapping station.  The robot control knows the appropriate number of layers to complete a pallet, eight in the case of Twirls, although the number of layers can be from four to nine according to case size, which varies from 296 x 239 x 115 mm to 594 x 394 x 253 mm to suit different products.

When a full pallet is complete, a twin-station pallet transfer car moves adjacent to it, powered rollers on both the conveyor and transfer car effect pallet transfer, and an empty pallet is put in its place on the conveyor.  The full pallet is transferred onto a turntable and stretch wrap is automatically wound around the cases to full height to secure the load.  Finally, the pallet continues out of the cell perimeter guarding via a safety light curtain to the end of the dispatch conveyor, from where it is handled by fork lift truck either to an internal warehouse or onto a waiting trailer for distribution to supermarkets, wholesalers, cash & carry outlets and CTM operators.

The height of a fully loaded pallet is typically 2.2 metres and the weight of each full case is up to 3 kg for bagged product, 5 kg for bulk product.  Health and safety concerns relating to manual loading are no longer an issue now that the Motoman robot stacks the pallets, and personnel have been deployed from this tiring and repetitive job to more amenable work within the factory.

When investigating the automation project at the outset and justifying capital expenditure, Red Mill considered the option of individual automated palletising robots to serve each of the five bagging machines.  However, periodic idle times precluded this solution, which in any case was more expensive overall. The beauty of the installed system is its ease of use, high flexibility and reliability with minimal need for operator intervention. Additionally, as the Motoman robot is picking complete layers of collated product and albeit the combined total throughput is high for this industry, it more than copes due to its high-speed capability combined with flexibility and versatility

A visit by Mr Faithfull and his team to Calypso Soft Drinks, Wrexham, where three turnkey robotic packing and palletising cells from Motoman place drinks into boxes and palletise 56 different product and pack size combinations onto shipping pallets in three different stacking patterns, indicated that the supplier's solution would work well at the Wednesbury factory.