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PLS speeds changeover, boosts reliability for Lever

A programmable limit switch speeds changeover and extends capabilities of new hot melt applicator and rebuilt filler.

Boxes of Sunlight laundry detergent, conveying upside down, are bottom-sealed (above) after scoop dropping and filling. At the p
Boxes of Sunlight laundry detergent, conveying upside down, are bottom-sealed (above) after scoop dropping and filling. At the p

At Lever Ponds Toronto, an effort is underway to modernize the plant's aging fleet of filling equipment for Lever's Sunlight brand powdered laundry detergent. One goal: replace mechanical components such as timing cams with specialized, high-speed electronic controls known as programmable limit switches.

The term 'programmable limit switch' is a bit misleading. It's actually a specialized controller that's far more sophisticated than what's implied by the word 'switch'--in functionality as well as price. By "reading" the position of the main drive shaft and translating that into carton position, these devices provide extremely precise package positioning information--more accurate than a PLC and sensors can provide on their own.

The PLSs are contributing to faster, more repeatable changeover, plus more reliable operation, according to company officials. On one line, a PLS has trimmed 30 minutes from a 90-minute hot melt applicator changeover and another 30 minutes from a 5-hour filler changeover. It has also reduced post-changeover trial-and-error adjustments on the adhesive applicators from 30 minutes down to as little as five.

Among the first machines retrofitted in the Toronto plant was a rotary-style volumetric filler on Line 2, which fills 1-, 2- and 3-kg boxes of powdered detergent. The filler was brought in from another Lever plant and rebuilt. It includes a Gemco programmable limit switch from Patriot Sensors & Controls (Clawson, MI). The PLS is actually a module that plugs into a Rockwell Automation/Allen-Bradley (Milwaukee, WI) PLC 5/40, also new. The PLC/PLS combo controls the filler as well as two new hot melt adhesive applicators from Slautterback (Monterey, CA). A local integrator, Sterner Automation (Toronto, Ontario, Canada), installed and programmed the PLS.

Easier for operators

The PLS control speeds changeover of the two hot melt applicators by allowing operators to enter the actual measurements--in millimeters--of where to start and stop the glue pattern across the length of the bottom and top carton flaps. The previous applicators also used PLSs, but they were more limiting. Operators had to enter numbers in "degrees"--actually the package pitch (distance from the center of one package to the next) divided by 360. That made it hard to judge precisely where the glue pattern should occur, resulting in some trial-and-error ramp-ups after a size changeover.

Now, the PLS, PLC and touchscreen display--a QuickPanel unit from Total Control Products (Melrose Park, IL)--all work together to graphically depict the adhesive pattern that will be applied. That provides visual confirmation of what the glue pattern will be before the packaging line is started up.

The benefit: as much as 75% less time spent on ramp-ups to ensure proper adhesive application, according to Dave Pearce, Lever's reliability coordinator. "We're very much improved over what we had before," he says. "It's not hit or miss like in the past." If minor adjustments do need to be made, an operator can make them on the fly. Before, a mechanic would have to make such adjustments, usually with the machine stopped.

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