Pick and place problems encountered on Unilever’s Twister ice lolly production line have been solved by installing new grippers from Bosch Rexroth
Twister ice creams are a summer favourite in the UK, so it’s not surprising that the production line at Unilever’s plant in Gloucestershire is one the busiest on the site.
“We run at a rate of 450 ice creams per minute, 24 hours a day and 6½ days a week,” said engineering technician Chris Burch. “It is the most booked and therefore the hardest working line in our Gloucester facility.”
Ice-cream distribution
Twister ice creams come out on plates from the freezers on a conveyor and a pneumatic hammer breaks them from the plate. At this point, a pick and place gripper comes across and distributes the ice cream onto an eight lane conveyor system from where the product goes on to packing.
However, there have been issues with the grippers, which pick and place the ice creams before packaging. They were creating problems within three weeks of installation with clear signs of wear. Also, the grippers were failing to properly hold onto the ice creams, and were letting them drop into the production floor.
“The issue we had was the reliability of the gripper cylinders which were supplied by a previous OEM,” said Burch. “We were finding that each cylinder only had a working life of approximately 3-4 weeks and were very costly to replace.”
Unilever estimates that the annual cost for the replacement of the 180 cylinders on the Twister production line was in the region of £16,000, before labour costs were factored in.
Alternative grippers
The decision was therefore taken to look at alternative suppliers of gripper technology.
“The gripper that had been specified was totally wrong for the job,” said Steve Morris, an expert in pick and place technology for food applications at Bosch Rexroth. “The Twister line was equipped with a 180° gripper from open to close which was at least two sizes beyond what was needed.”
Bosch Rexroth worked with Unilever to complete an accurate sizing calculation to ensure that any new gripper specified was suitable for the job. Once calculations were completed the decision was taken to trial two Bosch Rexroth GSP-A-25 grippers that only opened to the required 45°.
After several weeks in the field, an examination of the new grippers showed that there were no signs of wear at all. The decision was then taken to acquire eight sets of six grippers mounted on an angled mounting plate similar to that which was currently in use, along with manifolds for the pipe work.
Quick replacement
“We provided the grippers, fingers and plate in order to offer Unilever a total solution to the gripper problem, which would ensure that with any future maintenance a complete head could be replaced which would offer very fast changeovers and minimal downtime,” said Morris. “Now, with 2-3 bolts to put in a new gripper, the line can be up and running again.”
“Bosch Rexroth supplied a bespoke solution to our problems,” said Burch. “What impressed me was that they continued to work with us to find the best solution.”
The total outlay for the Bosch Rexroth Twister solution was approximately £14,000, but Unilever were unphased by the investment. “To be honest the cost of the solution was swallowed by the replacement and downtime costs associated with the previous grippers,” said Burch. “We now have a much more efficient solution which can be maintained much more easily and cost effectively.”
Putting ice-creams in their place
Pick and place problems encountered on Unilever’s Twister ice lolly production line have been solved by installing new grippers from Bosch Rexroth
Twister ice creams are a summer favourite in the UK, so it’s not surprising that the production line at Unilever’s plant in Gloucestershire is one the busiest on the site.
“We run at a rate of 450 ice creams per minute, 24 hours a day and 6½ days a week,” said engineering technician Chris Burch. “It is the most booked and therefore the hardest working line in our Gloucester facility.”
Ice-cream distribution
Twister ice creams come out on plates from the freezers on a conveyor and a pneumatic hammer breaks them from the plate. At this point, a pick and place gripper comes across and distributes the ice cream onto an eight lane conveyor system from where the product goes on to packing.
However, there have been issues with the grippers, which pick and place the ice creams before packaging. They were creating problems within three weeks of installation with clear signs of wear. Also, the grippers were failing to properly hold onto the ice creams, and were letting them drop into the production floor.
“The issue we had was the reliability of the gripper cylinders which were supplied by a previous OEM,” said Burch. “We were finding that each cylinder only had a working life of approximately 3-4 weeks and were very costly to replace.”
Unilever estimates that the annual cost for the replacement of the 180 cylinders on the Twister production line was in the region of £16,000, before labour costs were factored in.
Alternative grippers
The decision was therefore taken to look at alternative suppliers of gripper technology.
“The gripper that had been specified was totally wrong for the job,” said Steve Morris, an expert in pick and place technology for food applications at Bosch Rexroth. “The Twister line was equipped with a 180° gripper from open to close which was at least two sizes beyond what was needed.”
Bosch Rexroth worked with Unilever to complete an accurate sizing calculation to ensure that any new gripper specified was suitable for the job. Once calculations were completed the decision was taken to trial two Bosch Rexroth GSP-A-25 grippers that only opened to the required 45°.
After several weeks in the field, an examination of the new grippers showed that there were no signs of wear at all. The decision was then taken to acquire eight sets of six grippers mounted on an angled mounting plate similar to that which was currently in use, along with manifolds for the pipe work.
Quick replacement
“We provided the grippers, fingers and plate in order to offer Unilever a total solution to the gripper problem, which would ensure that with any future maintenance a complete head could be replaced which would offer very fast changeovers and minimal downtime,” said Morris. “Now, with 2-3 bolts to put in a new gripper, the line can be up and running again.”
“Bosch Rexroth supplied a bespoke solution to our problems,” said Burch. “What impressed me was that they continued to work with us to find the best solution.”
The total outlay for the Bosch Rexroth Twister solution was approximately £14,000, but Unilever were unphased by the investment. “To be honest the cost of the solution was swallowed by the replacement and downtime costs associated with the previous grippers,” said Burch. “We now have a much more efficient solution which can be maintained much more easily and cost effectively.”