DETROIT — Once considered a pricey technology used mainly overseas, low-pressure molding is mounting a challenge to standard injection molding and lamination for interior automotive parts made in North America.
Several Tier 1 suppliers and a Big Three automaker recently have adopted the process, which forms a finished part in the mold by chemically or mechanically bonding a resin-based substrate to a cover skin made with vinyl, fabric or film.
The technology has been used for nearly a decade by carmakers in Europe and Japan. Now, it is beginning to turn heads on this continent, said Siebolt Hettinga, chairman of Hettinga Technologies Inc. in Des Moines, Iowa. The 47-year-old equipment supplier was one of the first companies to sell low-pressure machines.
``In North America, we've seen it for door panels and for seating, and now we're going to see it for other parts,'' said Hettinga, whose company has added a new inverted-force machine that electronically regulates the mold front. ``Carmakers and suppliers have seen what it can do elsewhere.''
What it can do is save as much as 15-20 percent in time-consuming production steps and eliminate the need for environmentally unfriendly adhesives. However, startup costs to install low-pressure machines range from 10-50 percent more than conventional injection presses, industry experts said.
Since 1995, Ford Motor Co. has invested nearly $27 million in low-pressure equipment at its trim plant in Shelby Township, near Utica. The plant now molds vinyl interior panels with eight Williams-White vertical presses. The machines, which replaced 3,000-ton injection presses, make contoured door panels for the Ford Expedition, Taurus/Sable, Thunderbird and Cougar.
The process costs the 10- 15 percent less to make door panels than traditional methods, said Gerald Dominick, manager for advanced engineering at Ford Utica. Much of the savings comes from eliminating the need to spray adhesives on wood stock, which the plant had used as a rigid substrate, and pressure or vacuum form door panels after molding.
"Instead of shipping door panels to an adhesive-spray area, we're shooting little plastic pellets into the molding machine," Dominick said. "Our inventory and floor space savings are considerable, and we don't have to install emissions controls at significant cost."
Each panel is backed by a polyurethane foam pad containing polypropylene fibers. During molding , a PP substrate is injected at the back of the mold and bonded to the foam-backed vinyl. The presses have clamping forces of 1,300 tons.
The plant now expects to use as much as 15 million pounds a year of PP, compared with 4 million pounds under previous methods, Dominick said.
Tier 1 auto suppliers Lear Corp. of Southfield, Mich., and Blue Water Plastics Inc. of Marysville, Mich., recently followed suit. Blue Water makes vinyl and cloth seatbacks for Ford's Taurus/Sable lines and garnish panels for the Chrysler Sebring and Dodge Avenger with low-pressure equipment. Lear uses the process to make vinyl door panels for General Motors Corp.'s C/K -series light trucks at its Lebanon, Va.,plant.
Jack VanErt, Lear director of advanced processes, cautioned that lengthly tool changes and equipment costs are obstacles to the process's widespread use. With injection molding,