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Air care

Feb 1, 2009 12:00 AM

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DuraColor LLC, a $17 million printer in Racine, WI, has come a long way from a predecessor company's bankruptcy in 2004. The company's sales success has stemmed from its ability to meet tough deadlines with quality printing, which has enabled it to attract and maintain a stable of major clients. An ISO-9001-2000 company, DuraColor employs 60 and operates two shifts.

DuraColor does both standard and large-format printing and finishing for a number of Fortune 500 companies needing indoor and outdoor retail signage or product identification. Their clients are knowledgeable and discerning, explains Ralph Rhein, DuraColor's vice president of operations. Projects include murals, decals, foam signs, plastic printing, menu boards, store graphics and signage.

The company specializes in high-resolution screen printing, large-format 4-color graphics, and direct-to-substrate digital imaging. DuraColor prides itself on innovation in increasing the compatibility of large-format printing with high-resolution graphics, printing on a variety of synthetic materials such as acrylics, vinyl, plastic, PVC and polyester substrates. These materials build up electrostatic charges far faster than papers do.

A seasonal malady

Dry air problems in the Midwest are more common during the winter. When cold outside feed air is be warmed to comfortable indoor working temperatures, RH levels plummet. For instance, if 10°F air with 60% humidity is heated to 70° F; RH levels will drop to about 8%.

Specialized equipment can exacerbate dry air problems. Rhein explains that one of DuraColor's large 5-color inline presses, by itself, is capable of dropping RH to as low as 10%. “The press has UV drying lights cooled by a dedicated fan that sucks air and moisture out of the air at 1,500 cfm.

Maintenance manager Lance Warren recalls, “One time we had the press down for repairs, so the fan was off. The relative humidity was about 35%. When we started it up, RH dropped to 17% inside an hour. That meant trouble.”

“Difficulties from static can put a big dent in our productivity and press schedules,” Rhein notes. “In the past we've seen a five-hour job take as long as 12 hours because we had to slow the press to prevent jams caused by static cling. In a situation like that, you can't pass the extra time on to the customer. It just comes out of profit.”

Clean sheets

According to Rhein, a significant share of the company's better operating results come from a major reduction in the waste stream, especially in its direct to substrate digital imaging area. A major component in the waste reduction program has been a humidification system that automatically responds to plant air conditions, eliminating problems with static, which was attracting dirt and debris to digitally printed sheets of synthetic substrates. “It was brutal,” Rhein recalls. “The sheets cost anywhere from $3 to $30 each, and when things were going badly, we'd have unacceptably high nonconformance rates. It was costing us in a six-figure range every year.”

Unlike high-speed sheetfed or web printers, DuraColor's 60 x 102-inch sheets come off the press and stack up at about 250 sph. Each sheet is exposed for about 15 seconds before the next sheet runs off to top it.

If sheets are static charged, they attract dust, dirt and other airborne particles. The debris settles on the newly printed sheets and mars quality. The debris problem is most pronounced where DuraColor does direct to substrate digital imaging, which might go on the sides of semi trailers or gasoline pumps, and graphics for various retail applications.

If the floating dirt is not adequately controlled, nonconformance rates range as high as 60%, which scuttles productivity through both wasted time and material wastage. Rhein estimates that proper, consistent humidity control can reduce the lofting dirt by 70-80%.

Runnability issues

DuraColor was also troubled by other typical dry air problems: Static cling caused sheets to jam presses, and low RH shrank and warped substrates, causing issues with runnability and diecutting. Energy and maintenance costs were troublingly high.

Rhein has long realized the importance of maintaining proper relative humidity (RH) levels in DuraColor's 80,000-sq.-ft. plant: “Effective RH control during the dry winter months is essential to efficient production,” he says.

“We need to maintain RH at consistent levels of 50% at indoor air temperatures around 70°F,” Rhein explains. “For most of our printing, problems with static, shrinking, curling and other problems begin when RH drops into the 20-30% range. Without proper humidity control, especially in winter months, plant air can dip down around 10%. At that range, we'd have serious waste problems and would probably have to shut down the plant.”

Rhein adds that the combination of static, substrate shrinkage and presses that use semi-automatic and automatic feeding systems can result in improper feeding of sheets, jamming the press, creating major downtime and damaging stock.

From high cost to high pressure

“In the past, we've used both steam humidification and on-press static eliminators, and they've helped. But energy and maintenance costs were high and the problems persisted,” says Rhein

Warren recalls, “Our energy costs alone were nearly $10,000 a year, and we spent another $300-$400 a month on chemicals to reduce boiler scaling. Then every month or two we'd have to bring in a contractor to descale the boiler.”

Seeking a more cost-effective way to solve the problems, DuraColor investigated high-pressure humidification systems manufactured by Danish-based ML System a/s. ML's exclusive North American service provider, Husson Inc., was located just a few miles away in Sturtevant, WI.

“We looked at several options, but we were impressed with the ML system,” Rhein explains. “It has the capacity to provide the coverage we need throughout the plant, and it responds precisely to changes in our RH with the right amount of humidification. Our ROI analysis indicated that we could pay for the new ML system in less than two years with savings from the dusting problem alone. It wasn't a difficult decision at all.”

Within the DuraColor plant, 13 ML Princess 2 humidification units assure fast, even distribution of a fine, soft mist in a full 360-degree pattern. The 10-gph capacity units consist of a stainless steel nozzle ring with eight stainless steel nozzles. An integral fan enables fast, uniform mist distribution and allows humidified air to reach the far corners of the room. The fan operates at 55dBA — quiet enough to be placed near workstations.

Because RH conditions and requirements can vary widely in different parts of a facility, DuraColor's system is divided into four zones: screen prep, screen printing, digital imaging and finishing. Humidity sensors in each zone are integrated with a programmable controller, which monitors RH in each zone and responds to that zone's specific needs.

The controller manages each zone's cycle time and proportional band, adjustable for the size and type of the zone, air exchange, temperature and other variables. If RH is below the zone's set point, the PLC activates the Princess units until RH returns to its desired 50% level.

The four-zone system is served through a single ML pump station, with a maximum output of 2,000 lbs./hr. As debris and dust control is so important at DuraColor, spraying water with low mineral content is essential. This is accomplished by using a reverse osmosis (RO) water unit. As an extra measure of protection and purity, a UV filter at the pump station sterilizes the water.

Warren appreciates the system's low maintenance demands: “About all it ever needs is a simple filter or nozzle replacement — half an hour a couple of times a year. By comparison with our old system, the ML system is almost maintenance-free.”

Warren cites sharply reduced energy and operating costs. “With our gas-fired steam system, we spent $8,000-$9,000 a year on gas, electricity and boiler chemicals. With the ML system, we spend about $1,500 a year on electricity and nothing on chemicals.”

Rhein says the effect when the ML system was installed was immediate and dramatic. “People noticed the cool mist immediately. Their skin and their respiratory systems felt better fast. Within a couple of days, our static problems improved, and our problems with dirt and debris on the sheets improved by 75-80%. Problems with static-caused press jams largely disappeared, and so did stock shrinkage and warping. Our maintenance time and costs shrank, and our total energy cost to run the humidification system is about $1,500 a year, for electricity.”

“So many things don't perform as promised — it's great when something exceeds your expectations,” Rhein concludes.