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A well 'thawed-out' solution

J&J Snacks needed to automate pallet wrapping in its freezer warehouse. But only a specially insulated wrapper could function at temperatures as low as
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FILED IN:  Controls  > Strategy
     

Now approaching its 25th anniversary J&J Snack Foods has posted 24 consecutive years of sales increases. Soft pretzels are its specialty both for foodservice and retail channels. The Pennsauken NJ firm's Superpretzel line is the number one brand of soft pretzels in the supermarket trade. Sustaining this growth naturally requires constant evaluation of and upgrades in packaging systems. One good example of such an upgrade is in the freezer warehouse at the firm's Vernon CA plant. There J&J has installed an automated stretch wrapper from Wulftec (Ayer's Cliff Quebec Canada) that frees up several workers from the onerous task of using hand-held rolls of wrap to stabilize pallet loads. Even more important the automated system delivers a uniformity of stretch and a consistency in pallet appearance that couldn't be achieved with hand wrapping. The firm might have automated its pallet wrapping sooner but it had difficulty finding a machinery manufacturer that would guarantee its equipment would operate reliably in temperatures that average Enter Wulftec and its west coast distributor Gulf Pacific Packaging (Vernon CA). "Wulftec came to our attention through its western distributor" recalls John Carmichael chief engineer at J&J's Vernon plant. "They were willing to guarantee their equipment would do certain things for us and it has." It couldn't do those things however until Wulftec engineers added electric heating elements to motors and gears. The electrical controls are heated too. The programmable logic controller in particular a SLC 500 from Allen-Bradley (Milwaukee WI) must be kept at least 45°F to function properly. These modifications were all taken care of by Wulftec before the Model WCRT-200 rotary tower machine was shipped. But once the wrapper was in its new environment another problem had to be thawed out. Much of the machine's actions are pneumatically driven. This requires air lines of course and J&J quickly discovered that condensation gradually builds in those lines and freezes to block the flow of needed air. That meant more heating elements had to be added beginning with the central air regulator from which pneumatic lines branch off in various directions. In addition insulated electrical heating strips encase all pneumatic lines. Controlling all of this is a thermocoupling unit similar to the thermostat used for a home furnace. With it J&J can control the temperature of all pneumatic lines to keep air moving smoothly. Cold-resistant film Film was another issue. According to Gulf Pacific's Kathy Meyers four different stretch films were tested before J&J settled on an 80-ga linear low-density polyethylene from Intertape (Danville VA). The metallocene-based Stretch Flex I delivers the puncture- and tear-resistance the clarity and the load retention power that J&J required. It also proved more capable of withstanding the freezing temperatures than the other films tested says Meyers. "We're getting about 150% stretch on it" says Carmichael "which is fine considering the cold environment. They guarantee it to 200% and I'm sure it would do it but why push it?" Depending on the day's production schedule as many as six upstream packaging lines feed into the Wulftec palletizer. Workers in the freezer warehouse palletize by hand though Carmichael says an automated system is currently in the works. All cases enter the freezer warehouse on the same powered roller conveyor. After passing through a metal detector from Loma (Elk Grove Village IL) cases move down a conveyor spur that takes them past six manual palletizing stations. At each station when a pallet load is complete the operator transfers it to the powered roller conveyor leading to the stretch wrapper. this is done via a foot pedal that raises a series of transfer rollers submerged among the powered rollers of the main conveyor. The operator pushes the load onto these raised rollers. He then hits the foot pedal again and the raised rollers sink back down thus allowing the pallet to settle onto the main powered roller conveyor leading off at a right angle toward the Wulftec wrapper. Capacity to spare The stretch wrapper has all the capacity J&J requires. Carmichael says he appreciates the way as many as three full pallets can be queued up waiting for a wrapping cycle to be completed. And as soon as it is completed a photocell detects the exit of a load and signals the PLC to bring the next pallet in. Once a load is stationed in the wrapping area the wrapping arm starts slowly. When it reaches the top of the load it performs a couple of extra wraps and then moves into full speed as it makes its way back to the bottom. Once again a couple of extra wraps are applied. Then a roller pushes the film against the load and a hot wire cuts the film. Typically the tackifiers in the stretch film are sufficient to hold the film tail securely in place with nothing more than a wipe down. But in J&J's subzero warehouse the tackifiers are slow to cling so a heat-seal paddle follows the roller to seal the film tail securely to the side of the load. Getting the new stretch wrapper to operate smoothly in the freezer was a team effort says Wulftec's Bob Zwick. It's an effort that has J&J's Carmichael pleased. "They made a guarantee and they kept it" he says.

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