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Plastic Parts, Metallic Finish

Physical vapor deposition (PVD) is a high-temperature process often used to harden metal surfaces.

Physical vapor deposition (PVD) is a high-temperature process often used to harden metal surfaces. Which makes it totally incompatible with plastic interior pieces, like buttons and knobs. Until now. Preh Automotive (www.preh.com) has developed a low-temperature PVD process that is suitable for use with most interior plastics. "You need a vacuum chamber, clean room conditions, and a pristine surface for the best results," says Preh president and CEO Dr. Michael Roesnick. "And we prefer to control the process, from injection molding to application of the final finish, to guarantee the best appearance possible."

The finish applied can be aluminum, chrome, copper, or a brushed finish BMW–which uses the process on the HVAC controls of its 6 Series coupe–calls "ruthenium" for its platinum-like color. "We find that car makers use the process to differentiate between trim levels or models that use the same switches," says Roesnick, who adds that BMW added the finish to the HVAC controls of both the 545 and 6-Series mid-cycle. "Usually, the process is found on the center stack control knobs of premium vehicles," he continues, "though it also can be found on the VW Group's Polo and Skoda Fabia models as well."

Preh's PVD process deposits three thin layers of metal at 70ºC, and adjusts the look and feel–soft, hard, shiny or brushed–through the addition of a lacquer top coat. Illuminated switches also can use the PVD process as the lettering is laser etched into the surface toward the end of the procedure. "Unlike electroplating, there's no masking of the part, and much less scrap," claims Roesnick, "and it's cost-effective when compared to similar processes." Another plus is that the thin layers used in the PVD process don't transfer as much heat energy from sun load as solid metallic parts.—CAS