Fresh From The Paint Oven
PPG's Application Development Center has cooked up a number of new recipes for powder coating, from changing color on the fly to cutting drying time. The company hopes the new processes will drop more than over spray to the bottom line.
Three white “speed shapes”—sleek, curved automotive forms with harp fender peaks designed to mimic the ways light and color appear on avehicle—travel under the robotic spray arm at PPG’s Application Development Center in Flint, Michigan, and are covered in a glaze the color of dirty putty. Could this be right? Yes it is.
“The base coat mixes all of the powder we reclaim from the painting process,” says Rick Tansey, technical manager at PPG’s Automotive Powder Coatings division, “which makes this painting method very economical.” Not only does it eliminate the need to paint vehicles in batches so the over spray can be collected, cleaned, and reused, it uses 98% of the paint powder sprayed. “Normally, about 30% of the powder is over spray, and a good bit of that is never recovered,” says Tansey.
PPG calls this process “P2Zero” because it uses two powder color coats (the so-called “reclaim coat” and a color top coat) and has zero emissions. The clear coat goes on like powdered sugar, and dries clear when it is baked.“With this process, there’s no need for a mixing room to make material adjustments, the paint waste treatment and spray booth exhaust air treatment systems are eliminated, and there is no liquid waste,” says Tansey. In addition, PPG claims these advantages mean P2Zero takes less floor space than traditional spray systems.
Space and time are reduced further if the company's "Fast Flash" drying method is used. It employs a combination of controlled infrared heating and convection to remove water and solvents from the coating, while eliminating the "pops" and pinholes that usually accompany quick drying. "Fast Flash keeps the surface temperature to a relatively low 100ººF to 150ººF," says Don Emch, manager of Applications and Process Technology. "This produces less volatility, especially in the evaporation part of the drying process, than the higher temperatures normally seen in drying ovens." The combination of drying methods and the lower surface temperature apparently balances diffusion, evaporation, and dispersion, and can drop the dehydration oven cycle from 5 to 11 minutes to 45 to 90 seconds. "Fannon Infrared (www.FannonInfrared.com) worked with us to come up with this system," says Emch, "and together we were able to save $3-million compared to the cost of current infrared ovens." However, since time is money, the time saved ultimately might have a greater value. "With Fast Flash and powder coating, we can cut the total painting time from 154 minutes to 73 minutes," claims Emch.
Speed and cost reduction also are important factors for PPG’s Dynamic Flex Coat (DFC) painting system. The bell sprayer has multiple feed lines, and mixes the pigments at the atomizer, much like a color ink jet printer sprays a limited number of colors in varying combinations to produce a larger variety. While conventional systems typically offer 10 colors, the DFC color palette consists of approximately 160 choices. What’s more, the colors can be varied on the fly to produce custom paint effects, including the ability to create a two-tone finish in one operation.
“This changes the economics of low-volume painting,” says Vince Datillo, manager, Global Applications Technology. “One of the bottlenecks for the five-day car is the ability to offer the buyer a large color palette in a flexible manufacturing environment. Current practice is to paint cars in batches, but you can’t make a customer wait for his car until another dozen are ordered in the same color if you’re going to reach your goal.” The advantages of DFC reach well beyond the five-day car, however.
A study conducted by PPG and Behr Systems (PPG’s design partner on this project) for an OEM client showed savings of nearly $11/unit are possible with this method. Eliminating the door jamb cut-in on premium finishes by using a metallic primer coat saves $3.38/unit, and using a color primer saves a further $1.12/unit by requiring less top coat to cover it completely. The abbreviated two-tone process saves $6.39/unit.
In addition, DFC eliminates the need to purge and clean feed lines between colors, and can be used either as a low-cost functional, or a premium coating system. “When combined with the Fast Flash drying process,” Datillo says “Dynamic Flex Coat encourages the use of a small, ‘car wash’ style paint process that lets custom paint shops, fleets, as well as OEMs fit it into their existing infrastructure.”
Sitting in the wings is the company’s CeramiClear clear coat. According to Richard Zahren, vice president, Automotive Coatings, “If you look at the vehicles on the road today that have a clear coat, they look great for a while, but scratches in the surface cause white marks to appear, and dents smudge the finish, reducing the clarity of the top coat. It doesn’t take long before the finish looks dull and lifeless because the clear coat isn’t reflecting light as it once did.”
Zahren says PPG talked to its customers about the need for a more durable clear coat, and found a surprising amount of support. “Think about it from their perspective. A better finish can have a dramatic impact on the residual value of lease vehicles, and it certainly doesn’t hurt customer satisfaction. Each is a positive for an OEM.”
CeramiClear won’t eliminate all scratches, but it will resist them longer, according to Zahren. “You can still damage the surface with a key, but it’s much less likely that everyday bumps and dings, UV degradation, salt, or acid rain will affect the finish,” he says. And who wouldn’t like that?
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