For 20 years, Red Devil used turntable stretch wrappers to prepare pallet loads of its caulk, sealants and spackling compounds for shipment to retailers such as Lowes, Ace Hardware and True Value Hardware. But the Pryor, OK, company was having a devil of a time keeping the cases on the turntable once the machine started spinning.
"Our boxes are somewhat unusual because of their shape--they're taller than they are wide," says Alan Crupper, materials manager at Red Devil. "When the turntable started to rotate the boxes on the pallet, the centrifugal force would throw those boxes outward. We had $5ꯠ of damaged product [and packaging materials] a year." Operators often had to repackage the products because the impact of the fall from the turntable was enough to damage the product and/or the cases, he says.
During a trip to the Red Devil plant five years ago, Red Devil's distributor, Love Packaging Systems (Tulsa, OK), suggested using stretch wrappers with an overhead spiral carriage rather than revolving turntables. That would eliminate the incidence of tumbling cases. Since then, Red Devil has purchased three semi-automatic Cobra III stretch wrappers with an overhead carriage arm from ITW Mima (Tamarac, FL). The three semi-automatic machines are located in Red Devil's order-picking warehouse, where orders of several different cased products are hand-selected and manually palletized.
Eighteen months ago, Red Devil bought its newest ITW Mima machine: a Cobra XL wrapper. Unlike its semi-automatic predecessors, which are used for mixed loads, the Cobra XL is a fully automated system used exclusively for large orders of identical cases. It's fed by two upstream palletizers that are also dedicated to large, same-case loads.
Complementing the Cobra XL is an automated transfer car that relieves a forklift driver from having to take pallets from the palletizers to the wrapper. The transfer car boosts efficiency, Crupper says, because it greatly simplifies the forklift driver's task. Rather than spending time removing filled pallets from the two palletizers and placing them on a stretch wrapper, the driver now worries only about taking wrapped pallets to the warehouse.
Quicker wrapping
The Cobra XL wraps its loads in 80-ga, linear low-density polyethylene film. Supplied by ITW Mima, the film is prestretched 250% during application.
Product is automatically loaded into the 111/2"Hx8"Wx6"D corrugated shippers for 12-packs and 111/2"Hx16"Wx12"D shippers for 24-packs. After loading, the shippers are conveyed directly to the palletizers, which stack 120 12-packs per pallet and 60 24-packs per pallet. The filled pallet offloads onto the automated transfer car, which follows a track embedded in the floor to take the pallet to a powered roller conveyor feeding the stretch wrapper.
The Cobra XL is triggered by a sensor mounted to the infeed conveyor. As the pallet passes by this sensor, the Cobra's overhead spiral carriage revolves, wrapping the stationary load twice. Then, two pneumatic pulleys press the film into a taut rope, which travels around the load two times. Mechanical fingers catch the two "ropes." Then, a 1"-wide, heated bar with a nonstick coating moves up and presses the ropes together to create a strong weld. A heated knife moves up and cuts the film, and the pallet discharges from the wrapper to an outfeed conveyor, which can accumulate up to five wrapped pallets. Loads are taken via forklift to the stocking warehouse.
Improved productivity
Crupper praises the machine as a means to better allocate labor. "Now we don't have to have a forklift operator dedicating his time to picking up pallets from the wrapper. He can go do other things for at least 30 to 45 minutes before he comes and empties the line again." Crupper says the entire process, from palletizer to accumulation conveyor, takes about three minutes, compared to the five minutes it took with the turntable wrapper. "We can wrap about 125 pallets per 10-hour shift," he adds. That, plus no longer having to replace damaged product, adds up to a savings of about $15ꯠ a year, Crupper estimates.
