Industrial coating concerns are speeding up production, improving quality, reducing costs, and complying with state and federal environmental regulations by using advanced ultraviolet (UV) and electric infrared (IR) coating technologies recommended--and in some cases subsidized--by their local utilities. Fostering IR and UV technologies is a value-added service that provides a competitive edge for power companies facing deregulation.

An important link in the chains that connect coating companies, utilities, and the manufacturers of IR and UV coating equipment is the Electric Power Research Institute (EPRI) in Palo Alto, Calif. "It is natural for the research and development organization of the power industry to address coating problems, because energy studies of industrial manufacturing facilities have shown that the coating department is often the most energy-intensive," said Sal Lovano, a project manager at EPRI's Center for Materials Fabrication (CMF) in Columbus, Ohio.

As Lovano explained, coating is a multistage operation that requires cleaning the part with heated water and cleaning solution, applying a conversion coating or phosphate pretreatment, drying the part in an oven, applying the coating in a spray booth, and curing the coated part in an oven.

EPRI disseminates its technical expertise in coating and other industrial processes through its technology centers across the country that study specific applications of electric-based technologies. The centers are run by EPRI member utilities, including Southern California Edison, Georgia Power, and Pennsylvania Power & Light. Their continuing work benefits both utilities and coaters in industries such as wood finishing, automotive part manufacture, and wire coating.

Environmental concerns and a desire for speedier throughput were the main reasons the Lundia Division of MII Inc. in Jacksonville, Ill., needed to upgrade its coating line. Lundia manufactures wood shelving and storage systems, display racks, and mobile filing and storage systems for retail stores and offices. The company coats about 8 million board-feet of kiln-dried pine, fir, hemlock, birch, oak, and alder per year, as well as laminated plywood and particleboard.

Previously, Lundia used curtain coaters to apply clear finish to flat wooden panels. The curtain coaters consisted of a reservoir that poured finishing over a weir, forming a curtain of finishing through which the panels were conveyed. The coated products were then sent to tunnel-type convection ovens to be dried at 120 degrees F. "More profiled wood parts, such as frames, were sent to spray booths for clear finishing," said Gary Frye, general manager at Lundia's Jacksonville plant.

All pigmented Lundia products were sent to the booths as well. These items were painted, manually placed on racks, and air-dried. The process was repeated several times to build up multiple coats of paint. "Air drying took from 2 hours during dry weather to as much as 24 hours for pigmented coatings on humid days," Frye said.

Lundia used traditional lacquer-based finishes containing methyl ethyl ketone and toluene solvents to facilitate the degassing, flow, leveling, and spraying. Emissions of these compounds are regulated as volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) by the Clean Air Act Amendments of 1990.

Industrial Coating Services reduces its energy consumption and eliminates combustion by-products by using infrared lamps to cure the epoxy coatings on these Navistar engine blocks

The division first attempted to reduce the VOCs and HAPs generated by its coating processes by replacing its solventborne coatings with waterborne coatings but found none that provided the production throughput, surface-finish quality, or performance of the traditional finishes. It began to investigate ultraviolet-cured finishes in 1993 after attending an EPRI seminar on UV curing technologies.

Lundia found that installing a UV curing system would require raising its electrical consumption from 750 kilowatts to 1 megawatt as well as increasing natural-gas pressures and make-up air volumes to supply the UV-curing process in its existing pipeline system. The company approached its local utility, Illinois Power, for technical and financial support.

"Our long-term strategy is to get in on the ground floor with these new processing technologies and provide our customers with more than electricity and a bill every month," said Marty Behrens, the engineering supervisor at Illinois Power's Bloomington office. "We want to provide some additional value and services based on our expertise."

Illinois Power provided $15,000 in cash and consultant fees to Lundia for the UV installation, which was matched by an additional $20,000 from EPRI's CMF. A consultant presented Lundia with a description of UV curing systems, including procedures, that would suit the wood coater's requirements.

Lundia used this information to select a new UV flat-line finishing system developed by Cefla in Imola, Italy. The company purchased the Cefla system on a turnkey basis from Stiles Machinery in Grand Rapids, Mich. The $750,000 system contains a sanding module, optic sensors and paint-gun controllers, a paint booth with an overspray collection system, a stain wiper module, a convection oven for solvent flash-off, a fluorescent-light section, and two UV lamp modules. The finishing system was assembled, installed, and debugged within 10 days.

Wooden parts, which are fed into the system by a conveyor, are prepared for coating by two independently controlled sanders equipped with dust collectors. Photo-optic sensors read the shape and position of each sanded piece and feed this information directly into an Allen-Bradley programmable logic controller (PLC) that uses Cefla software.

The PLC controls the movement of four robotic spray guns on each of the Cefla system's two automated reciprocating carriages. These guns are programmed to spray a new, low-solvent UV coating mixture only when the parts are in line.

Computerized control enables the spray guns to apply highly accurate and consistent amounts of finish, creating coatings of more uniform thickness. Operators adjust the spray-tip size, atomization of coating, and pressure in the system to meet the required finish characteristics precisely.

A crucial component of the Cefla process is the hot air that preheats the finish to prevent the coating surface from curing before the base. After preheating, mercury vapor and gallium UV lamps cure the coating to a hard, stackable finish in less than 1 second. Once again, the UV-lamp intensities, temperatures, and internal pressures are chosen by the operators to suit the type of coating applied, its pigmentation, and its thickness. Because high-pressure UV lamps emit some infrared radiation, they can heat wood panels to the point that resins leach into the coating before it cures, producing an inferior finish. Lundia uses a system of inclined mirrors to reflect only the cool UV energy onto its products.

Northern Wire Products increased its production-line speed 50 percent by using this infrared booster oven to prepare its coated wire shelving products for a final cure in the existing gas-convection oven

The UV coating Lundia now uses contains ethyl acetate and butyl acetate solvents, which are not on the U.S. Environmental Protection Agency's list of hazardous air pollutants. An additional environmental advantage of UV-curable coatings is that they contain liquid monomers and oligomers that cross-link to form a solid-cured film upon exposure to UV light. This minimizes the amount of solvent needed, and thus released, during the drying step before UV curing.

According to Frye, the UV coatings are more uniform in color and thickness, more durable, and more chip-resistant than lacquer finishes. "The Cefla system has doubled our capacity," said Frye. "For example, a shelf that once required up to two days to paint and dry during humid days is now finished in 1 hour." Faster drying and curing times have also virtually eliminated smears caused by handling, and the accumulation of dust that previously marred finishes, he added. The UV curing system has also helped Lundia meet increased customer demand for pigmented panels, because the new pigmented coatings are cured more rapidly than the paints previously used.

The new coating system has optimized labor at Lundia as well. "We needed up to 12 people to man the four spray booths and sanders that were required on the old coating line," Frye said. "We typically use four people on the Cefla machine, and we were able to transfer the other eight to different departments at the plant. This machine is helping us grow our business."

Overspray generated by the spray booth was collected in filters that were replaced frequently. The automated precision spraying of the Cefla system reduces overspray to less than 10 percent of the previous quantity. This diminished amount is caught by a Mylar belt connected to a counterrotating roller that removes the overspray from the belt, to be directly recycled or reconstituted and used for base coating.

Since the success of the Lundia project, Illinois Power has instituted an Industrial Process Heat Program to promote electric-based heating technologies for processing industries. "This encompasses both an evaluation of the new technology and a financial grant to help our customers fund its installation," Behrens said. "In a deregulated power market, we want to be viewed as a preferred vendor, rather than one of several vendors."

Utilities sometimes bring advanced processing to coating companies along with new contracts. This was the case when Indianapolis Power & Light Co. (IP&L) was working with Navistar International Transportation Corp. in Chicago to find both a suitable epoxy-coating technology and a coating company for the diesel engines Navistar manufactures for its own trucks as well as for the Ford Motor Co. and others.

Utilities and their industrial customers reap obvious benefits from such collaborations, said Tom Beall, electrotechnology applications director at IP&L. "We advise our customers on innovative electric technologies that improve their process and productivity," Beall said. "The cost of any additional electric-energy consumption is more than offset by process and productivity savings, as well as fuel savings. Keeping our customers in business keeps us in business."

Navistar originally considered building its own coating facility, but with IP&L's assistance it determined that a local coating firm with electric IR curing technology would be more cost-effective. Navistar chose Industrial Coating Services (ICS), another Indianapolis-based company. IP&L assisted ICS with the IR technology and with system design, development, and installation.

ICS used a gas-convection oven to cure powder-coated and electrocoated automotive parts for Ford and Chrysler Corp. Coated diesel-engine blocks and heads required heating in the gas oven for 75 minutes at 475 degrees F. Because the entire engine block had to be heated to that temperature to cure, a cooling period of up to 2 hours was needed before the block could be packaged and shipped.

Navistar contracted for diesel-engine blocks and heads to be coated by ICS. However, ICS management was concerned that the stepped-up production required by the Navistar contract might necessitate an expansion of its Indianapolis facility or relocation to a larger site, both costly alternatives. A third option was to install an electric-based IR curing system, as IP&L recommended. Such a system concentrates heat on or close to the part surface, curing the epoxy powder before the interior of the part is heated throughout and sharply reducing powder-curing time. EPRI's CMF also assisted ICS with the technical details of powder-coating and curing parts with large weight-to-surface-area ratios.

The Cefla ultraviolet curing machine uses hot air to preheat the finish on wooden parts, preventing the surface from curing before the base. UV lamps cure the coating to a hard, stackable finish in less than 1 second

The electric IR system was custom-designed for ICS by ITW/BGK in Minneapolis and installed within three days. The ITW/BGK system cures powder-coated engine blocks 12 times faster, with one-fourth of the energy and less than 11 percent of the floor space required by the previous curing method.

Engine blocks and cylinder heads coated with epoxy powder are sent through the oven by overhead conveyor. The oven's interior is divided into three longitudinal zones, which are divided in turn into 23 vertical zones. A total of 544 infrared lamps heat the oven. An Allen-Bradley PLC contains customer-predefined programs for each computer-controlled heating zone within the oven. Operators select the appropriate program to cure the coatings of different-sized engine block and cylinder heads.

Curing times are now just under 6 minutes per diesel-engine block, compared with 75 minutes in the gas-convection oven. Cooling time has been halved to about 1 hour. An environmental benefit of the IR system is that, unlike the gas-convection oven, it does not produce emissions. As a result, no products of combustion are available to potentially contaminate the coating or the environment.

The small footprint of the electric IR oven enabled ICS to stay in its own building, because it required only 258 square feet of floor space, rather than 7,200 square feet for the gas-convection oven. The IR curing system consumes approximately 5 kilowatt-hours per engine block. ICS compared the capital costs to the energy savings and other benefits of the IR system, and expects the system to pay for itself in less than two years.

"IR-type curing systems are an expensive capital investment," said Ed Thomas, a chemical engineer and chief of engineering at the ICS plant. "It is important for coating companies to make sure their volume of production will justify the costs." Thomas added that industrial coaters should also factor in the elimination of emissions, reduction in fuel costs, and savings in floor space that an IR system provides.

IP&L fosters new and existing technologies such as the IR curing system through the Industrial Technology Advancement Center (ITAC), which provides hands-on technology demonstrations, assistance in implementing the new technologies, and special financial packages to facilitate installation. The utility contracted with AdvanceTek Inc., a nonprofit firm, to operate ITAC through the Manufacturing Technology Center of Indianapolis (MTCI), which IP&L helped form with the city of Indianapolis. MTCI's mission is to develop a skilled machining workforce in the Indianapolis area by providing member companies with training sessions and consulting services.

Advanced coating processes do not always require the complete replacement of existing curing systems. For example, Northern Wire Products Inc. (NWP) in St. Cloud, Minn., retained its existing gas-convection oven but incorporated a custom-made IR oven as well to boost production and to keep up with booming business.

A computerized ultraviolet finishing system enabled MII's Lundia Division to cure its wooden panels in a fraction of the time previously required while it eliminated volatile organic compounds and hazardous air pollutants

NWP epoxy-coats steel wire ranging from 1/8 to 1/2 inch in diameter. This is an aesthetic coating, because the wire is used as shelving by major discount and warehouse-type stores such as Wal-Mart, Kmart, and Hall-Mart. For years, the company used an overhead conveyor to move wire through a powder-coating station and into the curing oven. "Ten minutes curing at 400 degrees F meant we could move our coating line about 10 feet per minute," said Tom Romanoski, departmental manager at NWP. "However, our business was growing at 15 percent annually, and we were hard-pressed to meet demand running three shifts daily, six days a week." That demand would grow only sharper, because the busiest months for NWP are June and July.

Management calculated it would take a 50-percent increase in line speed, to 15 feet per minute, to meet the burgeoning demand. NWP first considered lengthening the existing oven but dropped the idea because of expense and space limitations at the St. Cloud facility. It then considered faster-curing powders, but found that its shorter curing time also reduced shelf life to as little as one month. The company decided to explore alternative curing technologies.

At the request of NWP, Northern States Power Co. in Minneapolis--under the auspices of its Drying and Curing Program--compared the cost of an infrared technology system with the amount NWP paid for natural gas to fuel the convection oven. The utility also provided NWP with the names of IR-oven manufacturers through its Manufacturer Network List and offered financial assistance.

NWP selected Process Thermal Dynamics in Brandon, Minn., to custom-design and install an IR booster oven that would work in conjunction with the gas convection oven at the NWP coating plant. The new curing system began operating in April.

The 13- by 6-foot IR booster oven is located at the entrance of the convection oven to partially cure coated wire before it is sent for final cure in the older oven. Coated parts entering the booster oven pass through a 4-foot vestibule, a 6-foot heated section, and a 3-foot unheated section. Eight IR emitters are arranged in four separate zones, each independently controlled, to enable NWP operators to select the appropriate IR output. Each emitter measures 16 by 68 inches and is rated at 16 kilowatts.

Wire leaves the booster oven 70 to 80 percent cured, before final curing in the gas-convection oven. "The combination of IR and gas-convection drying has sped our line up to 20 feet per minute for smaller parts, although typical speed is now 17 feet per minute, a 70-percent increase over the original curing system," Romanoski said. "This improvement would have required an additional 100 feet of convection oven." NWP spent approximately $22,000 to purchase and install the booster IR oven.

Because the various types of UV and IR curing equipment have proven themselves in the field, EPRI has launched three programs to improve the coatings themselves, to extend such coatings into other applications. For example, the organization is funding a program to develop IR/UV-curable powder coatings for wood and plastic substrates, which cannot withstand the cure range of 350 degrees F to 400 degrees F for standard powder coatings. "A short exposure to IR would cause the new powders to melt and flow, and UV would then cure the coating," said EPRI's Lovano.

Researchers at EPRI are also working on optimizing coatings that can be cured with electric IR alone, eliminating the need and energy requirements of gas convection curing afterwards. A third project will determine the effect of IR on powder coatings beyond the known time/ thermal relationship to improve their performance.

home | features | weekly news | marketplace | departments | about ME | back issues | ASME | site search

© 1997 by The American Society of Mechanical Engineers