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Lifting the lid on EZO can-end production

Walk through the canned goods aisle in any supermarket in Western Europe or Japan, and you're likely to notice at least one big difference from what you find in the U.S.: Easy-Open (EZO) cans are everywhere. By some estimates, as much as 90 percent of all canned foods on the shelf in parts of Europe and Asia are packaged with an end that pulls off rather than one that requires a can opener. For consumers, the benefits of the EZO end include greater ease in opening and the ability to remove can lids on-the-go—a huge advantage or today's convenience-driven society.

For Scotland's Baxters Food Group, Ltd., the switch several years ago from traditional sanitary can ends to Lift Off(TM) (formerly referred to as Eole III(TM)) EZO ends from Crown Holdings, Inc. (www.crowncork.com) for its canned soup lines has resulted in a significant increase in sales and market share. "As a premium brand with a commitment to customer convenience, Baxters needs to stay at the forefront of packaging innovation," says Claire Quigley, brand manager for Baxters Ambient Soups. "The Lift Off end allows us to take advantage of the newest packaging technology without compromising the exceptional production and quality standards associated with the Baxters brand."

Originally developed by Crown's research and development team in Wantage, England, the steel, Lift Off full-panel, easy-open lid is manufactured at several facilities in Europe and in Massillon, OH. In 2002, the Massillon plant became the first in the world to produce the 307-dia, double-reduced (DR) steel, full-panel Lift Off lid.

In operation for nearly 140 years, Baxters is a family-owned business providing premium-quality brands of soup, preserves, condiments, sauces and other specialty-food items. Since the business was founded in 1868, its motto, "Be different, be better," devised by founder George Baxter, has always meant constantly searching for the best ingredients and the most exciting new recipes. This philosophy also extends to Baxters' packaging, relates Quigley. In fact, Baxters was one of the first major U.K. brands to can its food products in the early 20th century.

Therefore, the company was quite intrigued with the development of the easy-open end, since the packaging increases customer convenience by eliminating the need for can openers, provides a seal integrity equivalent to traditional sanitary ends and broadens product appeal. After carefully researching the user-friendliness of various easy-open ends, Baxters chose Lift Off ends for all of its 415-g soup cans. This includes packaging for all of its Traditional, Luxury, Healthy Choice and Vegetarian soup lines, sold in the U.K, U.S., Australia and Canada.

"We take great pride in developing the best products available," says Quigley. "Customers always appreciate improvements that make their lives simpler, and Lift Off represents the latest technology in ease of use."

The lids for the 73x115-mm soup cans are printed with a three-step, "how-to" illustration that guides consumers through the easy-opening process. Quigley notes that this method of familiarizing the consumer with the process has resulted in speedy market acceptance of the new packaging.

In addition to achieving success with consumers, Lift Off also was easily integrated into Baxters' existing packaging processes. According to Quigley, the conversion of the production line was simple, with no major expenditures required. "The transition process was simple to implement, and our position as an innovator was enhanced," she says. "Lift Off certainly contributed to our sales increase last year."

Easy-open food-can ends—or ends that use a ring-pull, pop-top lid to enable the user to partially or completely remove the can end to spoon or pour food from a can—were first introduced in the 1960s for use with aluminum cans. In the late 1990s, new technology enabled manufacturers to design less-expensive EZO ends made from steel that could be removed as easily as aluminum EZO ends.

The challenge met by Crown in engineering its Lift Off end technology is to control a 125-ton press operating at 30 ends/sec to achieve a score that varies by no more than 10 microns.

Today, research by the Can Manufacturers Institute (CMI) (www.cancentral.com) estimates that EZO ends can be found on one-third of food cans sold in the U.S. market and predicts that this number will climb to more than two-thirds by 2008. CMI's information also indicates that consumers are willing to pay more per package for an easy-open lid on their canned foods.

The challenge for can-end manufacturers such as Crown in getting U.S. food packagers to adopt EZO technology on a wide scale lies in migrating the concept away from subjective opinion to hard science that is measurable and consistent, explains Ray McGowan, president of Crown Food Packaging USA. "We know from market research that consumers want the convenience of EZO cans," he says. "Our job is to demonstrate to food processors how to meet that demand with reliable technology based on science, not assumption or opinion."

To accomplish that, Crown has invested heavily in the science of EZO can ends, with research centers in place in Alsip, IL, and Wantage, U.K. According to Terry Benge, a director specializing in food packaging at Crown's Wantage plant, the introduction of advanced, harder, DR steel was essential to the development of Crown's Lift Off technology. "It gave us what we needed to consistently manufacture the ends to meet exacting requirements," he says.

Presently, Crown is the only supplier in the industry to use DR steel for large-scale manufacturing of EZO ends. According to Crown, because DR steel is harder than the materials previously used to make can ends, and therefore more conducive to the creation of lighter ends, it performs two opposing roles in the EZO application. First, it offers the pressure-resistance and strength required to stand up to the rigors of retorting and seaming during the packing process, as well as to endure the shocks, vibrations and other stresses encountered when the final package is transported and then handled by the consumer. Second, the end's lightweight metal construction lends itself to easier removal by the consumer, requiring less energy to remove the panel once the score has been pierced.

When developing Crown's Lift Off ends, Benge and his colleagues were tasked with not only creating a truly "easy" experience for the consumer, but also of doing it in such a way that it would be economically feasible for Crown to manufacture and for food processors to use on their packaging lines. However, Benge says that the real benefit from the science of Lift Off is realized in how the end performs for the final consumer. "For this, the manufacturing process is concentrated in two particular areas," he explains, "'scoring' and 'rivet making.'"

Crown's Massillon plant operates multiple production lines in three buildings covering in excess of 240,000 sq ft of manufacturing space. The plant produces close to 3 billion can ends/year in more than 200 different styles. As Massillon plant superintendent Jim Skinner told PD during a recent visit to the facility, a majority of the ends manufactured at the plant are traditional, non-EZO, sanitary can ends, with the balance comprising aluminum EZO and DR steel Lift Off ends. Additionally, the plant manufactures two-piece food cans.

While Skinner says that the plant does produce some custom ends, he explains that its standard-diameter designs can also be produced in a range of thicknesses, with different enamel coatings and in different colors, as well as with other options, depending on the end use. Lift Off DR steel ends are produced in 307-dia version only, at this time.

In Massillon, the Lift Off ends are produced during three shifts, over a 24-hr/day, five days a week. The manufacturing process for these can ends begins when sheets of steel, supplied by a range of vendors and coated, printed and cut by Crown's Weirton, WV, facility, are run through an electrostatic waxer that provides an even mist of wax across the sheets to lubricate them in preparation for the drawing process.

After further processing, can ends then move through a high-speed, compound rotary liner from Preferred Machining Corp. that applies a precise bead of water-based compound sealant around the inside of the curl to act as a sealing gasket between the end and can. Explains Skinner, "The lid is spun, and after it gets up to speed, a compound nozzle gun applies lining compound around the end. When that operation is done, we basically have what we call a lined shell."

To ensure that the liner has been applied properly and that there are no other defects in the lined shell, the ends then move through a vision system that provides consistent lighting, snap-to-snap. Out-of-tolerance or defective ends are automatically rejected from the line, while shells passing muster are carried through an oven that dries the compound liner.

The next stage in the process—can-end conversion—is where Crown's patented Lift Off technology is incorporated. Through the use of a conversion press from The Minster Machine Co. (www.minster.com) and a Stolle (www.stollemachinery.com) System H die set, the shell undergoes more than 10 separate operations that convert it to a finished, tabbed end. During conversion, the press adds anti-rotation beads to the end that will keep the tab from rotating, as well as tab-lift beads that provide better access to the tab; apply a rivet to hold the tab onto the can; and score the end to provide a tear line around its circumference.

The riveting process is crucial, because once the Lift Off end is assembled, it has to perform as promised, with the tab remaining attached to the end during the opening process. This is essential, as the bottoms of two-piece cans cannot be opened with a can opener if the tab breaks off.

Also critical to the proper functioning of the Lift Off end is the precision of the scoring process, which incises the steel shell by two-thirds of its depth. The challenge met by Crown in engineering its Lift Off end technology is to control a press operating at a high speed to achieve a score that varies by no more than 10 microns, while simultaneously carrying out 29 other forming operations.

Meanwhile, a 10-station progressive die forms the tab from a strip of steel that enters the machine from the side. When both tab and lid are formed, they are assembled in the machine and undergo an in-press strobe test that inspects for perforations.

After conversion, can ends move through a Sardee (www.sardee.com) regulator that provides accumulation, after which they are conveyed to spray-application machines that apply a polymer epoxy spray on the outside of the end and over the score cut, to protect the score from rust. The ends are then conveyed up a screw elevator and down a cooling tower.

Rigorous quality inspection takes place throughout the remaining processes, which finally lead to an automatic bagger from Sardee that loads the ends into paper sleeves.

For the Lift Off end, as with all EZO ends, success is judged by four metrics: tab access to lift the tab, pop force to pierce the score, tear force to initiate the peel and peel force to remove the panel. With this in mind, Crown's Massillon facility employs daily quality checks that duplicate the can-end opening experience. Additionally, operators check the compound weight, the unit depth, beads and the lid's outer diameter, as well as in-process checks on the conversion process.

"We are seeing a lot of success with the Lift Off end," relates Skinner. "Reliability is key; it has to work one hundred percent of the time. We take it very seriously that the end opens. We have to give the easy-open experience to people every time."

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