Budd Co. and resin supplier AOC LLC said they have revamped their formula for composite body panels, producing fenders, hoods and other parts that automakers can paint in-house with far fewer problems. The improvements could lead to more sales for plastics.
The jointly developed Atryl TCA makes it possible for automakers to treat body panels made of sheet molded compound the same as steel panels in the paint shop, but with a reduced likelihood of aesthetic flaws. That means less scrap, lower costs and an ease of use that could land more material decisions in composites' corner.
The new recipe went into production in the spring for a cross-section of Ford Motor Co. vehicles, starting with outer truck box panels on the Explorer Sport Trac. The formula now is used on the Mustang Mach 1 hood, the Ranger pickup truck hood, fenders for the Lincoln Navigator and the hood, fender and deck lid on the Thunderbird.
Those products all are getting high quality marks from the assembly plants, said Mike Dorney, vice president of sales and marketing for Budd, a Troy, Mich.-based division of ThyssenKrupp Automotive Co.
``We have days now where there are zero defects,'' he said. ``We didn't have that before.''
At issue are tiny flaws that occur on the painted surface called ``edge pops.'' The flaws resemble small, deflated air bubbles and are listed as the biggest obstacle to future SMC growth. They turn up typically when composite panels are painted at the assembly plant alongside steel units using paint methods developed for metal parts. They show up at the end of the line, when scrapping a part is most inconvenient and expensive.
Edge pops are not an issue when composites are painted separately, said Probir Guha, manager of research and development for Budd - and they are not a structural flaw.
Automakers do not want to run separate paint lines for metal and plastic panels, and having suppliers paint composites outside the plant can increase piece costs, Dorney said. In addition, there is greater potential for a poor color match when the panels are not painted simultaneously.
So Budd and AOC - the Collierville, Tenn.-based supplier of the vinyl ester used in Budd's SMC - launched a five-year research project to determine the underlying problem and how to fix it.
The studies linked the paint flaws to microscopic cracks in the composite that provided a site for paint solvents to collect, Guha said. When the solvents evaporated during the paint-baking cycle, the deflated paint bubble was left behind.
``All the previous efforts to correct this were reactive,'' he said. ``We wanted to look at the root cause.''
The companies created a new vinyl ester for the SMC that toughened and smoothed the surface, reducing the potential for cracks. Laboratory tests showed a 90 percent drop in the number of flaws.
``[Original equipment manufacturers] don't want to know what their panels are made of, they just want to treat it all the same,'' said Michael Dettre, business manager for AOC's closed-mold resins.
Ford now is using the panels at a variety of assembly plants and may expand their use. Budd is in talks with other automakers.
The companies also will make the material available to other processors, either through the purchase of a final mix prepared by Budd or through independent development efforts with AOC, Dettre said.