Composite Products Inc. of Winona, Minn., later this year will commercially launch a novel, high-volume, closed-mold thermoplastic composite process that will be used to fabricate structural automotive components. The technology, known as injection transfer molding, was developed by Composite Products during the last two years, and builds upon a previously unveiled open-mold processing technique. Company officials claim injection transfer offers both technical and economic advantages over glass-mat/thermoplastic compression molding and long-fiber injection molding.
The firm is ramping up an automated injection transfer production cell at its Winona manufacturing plant, and expects to mold first-run trial parts in August. Full commercial production is slated to begin in December, with an annual yield of 400,000 parts.
The process will employ multi-cavity molding; 100,000 sets and four parts per set, President Tom Prussia said.
Company officials declined to identify the automaker purchasing the parts, other than to say it is one of the Big Three. The parts will be used on a 19961/2 vehicle platform - a model to be sold in the United States and Europe. The parts will be structural in nature, but also must conform to external appearance surface requirements, and will incorporate localized areas of molded-in surface texture.
Prussia said his injection compression technology was chosen over competing bids from nylon injection molding and polypropylene compression molding systems.
In a separate program, Composite Products is licensing the injection transfer technology to another automotive parts supplier, with production scheduled to begin in 1997. That project will involve molding structural seat components for a 1998 vehicle platform.
Prussia said the company's thermoplastic composite molding technology mainly is targeted at automotive weight-bearing structural members and body pillars. The technology is not considered a candidate for large body panels or exterior effects such as spoilers or bumper shrouds, due to limitations on surface properties that results from high glass loadings. Parts being molded in the December project will have a glass loading of 40 percent, with fibers one-half-inch to 1 inch long. PP is the matrix resin.
Ron Hawley, vice president of research and engineering, said the injection transfer technology was designed to mold complex-shape structural parts in an automated, closed-mold operation. The system involves a hot, compounded billet, which is injected directly into a closed mold, and requires no further compression. The company has patented the tooling and processing aspects of the technology and is seeking licensees.
Tools can be designed to accommodate parts with a wall thickness from 2.5-6 millimeters, Hawley said. Functional part sites, such as bosses and fasteners, can be incorporated into the mold design. Unlike glass-mat, the process can support part designs with complex geometries and rounded edges.
Composite Products is evaluating nylon and thermoplastic polyester for future programs. Injection transfer represents the next generation of a thermoplastic composite molding technique unveiled last year by Composite Products. The company licensed two systems in 1994 to MAD Products of Cleveland, and Grand Rapids, Mich.-based Auto Style Plastics Inc., a unit of Marco Inc. Both licensees are producing automotive parts in a compression molding operation.
Earlier this year Composite Products installed a similar open-mold system in Sweden for Volvo ABA, which now is being used for captive production of under-hood structural parts.
The front end of the process, for either the open- or closed-molding version, incorporates the compounding of dried resin pellets, long-glass fibers, and various chemical additives. The materials are metered via separate gravimetric feeders into a single-screw extruder.
HPM Corp. of Mount Gilead, Ohio, builds the extruder to Composite Products' specification. The system compounds materials and moves them into a separate preform accumulator vessel which produces a hot billet of compounded material, ready for molding.
Hawley pointed out this stage represents the most proprietary aspect of the system, as the compounding technology is designed to maintain the integrity of the long-glass fiber reinforcements. Hawley said that conventional injection molding techniques typically chew up the longer fiber lengths, while also experiencing flow difficulties and weak knit lines in molded parts.
Prussia said his compounding technology virtually eliminates the unreinforced, resin-rich areas often found in glass-mat parts, while substantially reducing the part scrap and post-mold trimming typically associated with glass-mat. Injection transfer offers a cost structure of about 31/2 cents per cubic inch, which is comparable with existing thermoset methods such as sheet molding compound.
