Compact Robotic Handling of Mushy Peas


At the Derbyshire factory of Lockwoods, the leading manufacturer of frozen mushy peas with an annual throughput of 4,000 tonnes, Motoman robots have taken over packing of bags into cartons in one of two cells serving the palletising area, which itself was robotised in 1998.

The majority of the heavier bags of peas, weighing either 1 kg or 907 grams (2 lbs), are processed through the robotic side to save the two operators in the adjacent cell the arduous task of stacking them into boxes by hand. Although the large bags do occasionally go through the manual side, it is usually reserved for packing smaller product weighing 454 and 750 grams.

A striking feature of the latest automation project at the Ambergate factory, 10 miles north of Derby, is the very small area into which the twin-robot packing cell has been shoehorned. Within an area of less than 9 sq m, a Motoman SK16 six-axis robot fitted with a collator attachment picks up five 1 kg or six 907 gram bags at a time from the end of an input conveyor and places them into a cardboard carton with capacity for 10 or 12 bags respectively. A smaller SK6 six-axis robot within the same floor area erects cartons and places them beside the SK16 for filling.

Said Richard Spencer, Lockwoods' production director, "Normally a case-erecting machine is a colossal size, but the small Motoman robot manages to do the job in a fraction of the space. The other breakthrough was the multiple bag handling technology that Motoman introduced, following successful implementation of a similar collating gripper system in Finland."

He went on to point out that, although the manual cell can keep up with the robotic packing side for short periods, frequent staff changes would be needed to maintain this pace. In any case, such performance is only possible with experienced operatives of which there is a limited supply, especially at 7.00 am - the start of the first shift - due to the limitations of local public transport. There is also the issue of repetitive strain injury to consider when employing people to do this type of work.

This latest project follows the successful implementation on-site of a Motoman SP100 dedicated 4-axis palletising robot. Serving two pallet stations, it picks two cartons at a time off the conveyors from the packing cells, building the pallet loads by stacking 10 cartons per layer, eight high. A special gripper system was supplied with twin forks and an overhead clamp at one end for handling the cartons; while at the other end, two bespoke clamps are used to pick up freezer spacers from a pile and place them between the layers of cartons.

After each fully built pallet has been taken away by forklift truck to the blast freezer, the robot has a yet another duty. Using the same gripper as is employed for carton handling, a new pallet is picked up from a stack within the cell and placed in position ready for loading.

Continued Mr Spencer, "Motoman was awarded this contract because the other suppliers we looked at either wanted to specify two robots to load the pallets, or said the roof height had to be raised to provide clearance for robot operation. Neither stipulation proved necessary."

Now that the uncooked mushy pea packing area has been successfully automated as far as is feasible, the intention is to investigate how robots can assist product handling in the adjacent cooked range process line.

Mr Spencer's concluding comments concerned robot reliability, which is paramount for maintaining productivity. He said that the palletising robot has been serviced once a year since it was installed four years ago, since which time its operational availability has been 100 per cent. He confidently expects similar long-term performance from the other two robots.