Liquid Clinic: UV Waterborne Flatline Spraying

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Q. We have been asked to put a finish on some wood products. What can you tell me about UV flatline spray finishes?

A. UV flatline spray finishing has helped manufacturers of kitchen cabinets, wood furniture and flat wood building products increase throughput and product efficiency for several decades. 

These systems use a conveyor to move flat objects such as doors and panels under a spray. Some systems use an oven to remove water in the coatings to promote adhesion and avoid issues such as blisters and bubbles. UV lamps support a fast cure. Conventional vertical dryers can take from 45 to 60 minutes to dry conversion varnish; today’s waterborne UV flatline systems require less than 10 minutes to deliver a durable finish. This provides manufacturers the ability to handle and stack materials immediately without fear of blocking and marring.

Traditionally limited to clear coat solvent-based finishes, UV spray flatline finishing has seen growth as waterborne clear coats became available. But UV spray flatline finishing has begun to grow rapidly due in part to consumer demand for painted cabinetry. Extremely popular among younger home buyers and remodelers, the market for painted kitchen cabinets has grown to over 50 percent of the new-build and remodeling markets. Painted cabinets allow consumers to completely transform the look of a kitchen with a relatively small investment. 

While manufacturers may also use traditional solvent-based coatings to meet these needs, the recent introduction of waterborne UV pigmented finishes enables them to achieve the same durable results faster, in an environmentally preferable manner, producing customized cabinetry more quickly. 

A coatings supplier may offer a standard color offering of waterborne UV flatline coatings. And while whites and grays dominate today’s market, the new technology enables cabinet manufacturers to produce cabinets in virtually every color in a coating supplier’s fan deck. This allows a cabinet manufacturer to easily supply cabinet accent pieces, such as kitchen island cabinetry in a color that contrasts with primary cabinetry and appliances. 

But that doesn’t mean the cabinet manufacturer is stuck with gallons of a coating that may never be used again. Coatings suppliers should be able to supply specialty color batches through local facilities in volumes as small as a single gallon.

Batch-to-batch consistency is another strong benefit as the waterborne UV flatline coatings process maintains quality control finishing specs within a tight range, delivering accurate color and gloss matches. Dialing in a finish to perform consistently on a variety of wood species is simplified. This allows a manufacturer to produce different cabinet components on different days without the worry that part color and gloss won’t match upon assembly. Waterborne finishes also enhance adhesion properties, delivering a durable, long-lasting finish. 

Waterborne UV flatline finishing is also environmentally preferable to solvent-based finishing to help a cabinet manufacturer achieve sustainability goals. The coatings offer an approximate 20 percent improvement in transfer efficiency over solvent-based systems. Up to 85 percent of overspray may be reused. These results are achievable in a properly designed and maintained system. The coatings carry no formaldehyde and include low VOCs as well. And due to the significantly shorter cycle, drying and cure times, energy use is reduced.

Waterborne UV flatline finishing can help manufacturers that are operating in a state or region in which VOCs are limited remain in compliance. As an example, one California-based manufacturer reports that his company stays well below the allowable monthly limits
of  VOC that can be sprayed since a move to waterborne UV finishing. 

There is a cost associated to implement the technology in terms of replacing traditional vertical dryers and addressing a learning curve with finishing employees. However, that cost is offset over time through an overall reduction in applied cost, calculated through increased throughput and the use of less coating material through reuse of overspray, reduced energy use, plus the added benefits of color and gloss enhancements. 

Manufacturers seeking to learn more about waterborne UV flatline coatings should work with a coatings supplier that is well versed in the technology. That supplier will likely have an affiliation with UV flatline equipment manufacturers. This team can work with manufacturers to plan new finishing lines and get them up and running quickly to provide a significant competitive advantage.   


Nick Bartoszek is the global marketing product director, wood finishes, for Sherwin-Williams.


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