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Article | February 1, 2013
Cartoning made simple
What used to take six operators now requires just one as Schiff Nutrition automates its cartoning operation. At 400 nutrition bars/min, the speed is pretty impressive, too.
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Occasionally the ROI on an automation project makes it so attractive it becomes easy to justify the upfront investment. That’s pretty much what happened recently at Salt Lake City-based Schiff Nutrition. Secondary packaging of Schiff’s flow wrapped Tiger’s Milk nutrition bars was being done manually by six people. Now five of them are occupied in jobs less ergonomically taxing while an automated solution takes care of the cartoning tasks they used to perform.
Carton erecting, carton loading, and carton sealing are all neatly arranged in a compact, U-shaped line provided by Delkor (www.delkorsystems.com). First is carton erecting, done on a Delkor Trayfecta system. The 24-pt SBS cartons are printed offset in five colors.
“We have two bar sizes and two carton sizes,” says Jordan Rettig, packaging engineer at Schiff. “But we spend zero time on changeover at the carton erector. When we run the smaller 35-g bar, we only load cartons into one magazine on the carton erector. For 55-gram bars, we load the other magazine. It makes a huge difference in terms of efficiency when you don’t have to change forming tools or carton erecting tools on machinery.”
The Trayfecta carton former uses vacuum cups to pick flat blanks from one of the two magazines mounted on the machine. The blanks are laid flat on an indexing device that moves them into a plunger. With each downward stroke of the plunger, a blank is squared up and glued into a carton whose top flap remains open.
Schiff cut the cost of its cartons by switching from an auto-bottom, tuck-style carton to a carton whose flaps are folded and glued. Additional savings came with the elimination of a clear film overwrap. “It used to provide a measure of tamper evidence,” says Rettig. “But with the glued flaps, it’s really not necessary.”
One discovery regarding the cartons had to do with dimensions, which had to be expanded slightly. “A human can squeeze primary packages into a carton in a way that a robotic end effector can’t,” says Rettig. “The robot needed a little more clearance, especially at these speeds.”
Cartons are conveyed around a 90-degree curve single file and enter a Delkor Robotic Loader anchored by a Fanuc M-3 robot arm. Also being conveyed into this machine are the protein bars themselves. These are wrapped in a two-layer extrusion lamination of 80-ga Oriented Polypropylene and 60-ga metallized PET. The OPP is reverse printed in five colors on a gravure press. A pattern cold seal provides the means by which the flexible film is formed and sealed around each bar, and the date code is printed on the inside of each fin seal.
While the Formost Fuji flow wrapper has been around for some time, a checkweigher from Mettler-Toledo Hi-Speed is a new addition. Any bar whose weight is outside of preset parameters is automatically rejected.
The protein bars move into the robotic load cell at an impressive rate of 400/min when the 35-g bar is in production. They enter a servo-driven carrier that takes them at a right angle in groups of 12 and positions them where the robotic end effector can pick them. With each cycle, vacuum pickup cups on the end effector of the robot arm pick 12 bars and place them in two waiting cartons. For the larger 55-g bar, the format is two layers of six for a total of 12 protein bars per carton. For the smaller size the format is four layers of six for a total of 24 protein bars per carton.
Two servo-driven carriers
The only way to keep up with the 400 bars/min speed is to use two servo-driven carriers. So the two are mounted on a sort of an oval-shaped race track device. While the vacuum cups are picking bars from one carrier, the other one is being filled. When one is emptied of its bars, it quickly follows the oval-shaped track back to the station where incoming bars can fill it, and the freshly filled carrier moves in to have its bars picked.
A photoeye from Sick detects the spacing of the bars as they shoot into the robotic cell. If any bar is crowded so tightly against another that it might cause a jam when it reaches the servo-driven carrier, a burst of air kicks that bar off the line. A second Sick photo cell ensures that 12 bars are in the servo-driven carrier, and if any are missing, that carton is later rejected.
Filled with their full complement of protein bars, the cartons are discharged from the robotic cell and make a right angle turn into the Delkor Capstone M Closer. First a stationary overhead bar pushes the top flap down as the carton is pushed beneath it. Once in a fixed position, adhesive is applied to the three sides of the carton by a Nordson device. Then pneumatic arms close on the three sides and hold the flaps briefly until the adhesive has set. Finished cartons then pass through a laser coder from Markem-Imaje before being discharged from the carton closer.
“Durability and ease of use were our requirements,” says Rettig. “I also wanted to be sure there would be no drop-off in speed. Delkor responded with a servo-driven, all-stainless steel solution. And by giving them turnkey responsibility, we eliminated some of the complexity that can creep in when you are dealing with multiple machinery vendors. For example, even before the Factory Acceptance Test at our own plant, we were able to conduct a pre-FAT at Delkor’s plant. We wanted to watch it running at 400 bars per minute before even taking it to our facility. That would have been difficult to arrange if more than one machine builder was involved.”
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