Long-fiber thermoplastic process cuts cost of auto parts.

A new process for compression molding automotive and other structural composites from long-glass-reinforced thermoplastics is said to offer advantages in economics, processability, and part quality over processes using glass-mat/thermoplastic (GMT) sheet.

The novel molding technique from Composite Products Inc. (CPI), a processor based in Winona, Minn., involves compression molding an extruded "hot log" of reinforced compound. That compound is produced directly from glass and resin in a single step, eliminating the expense of buying pre-compounded material.

CPI is licensing its proprietary technology and building turnkey manufacturing systems for two domestic and one European automotive parts producers, as well as ramping up its own in-house parts production.

As in GMT sheet (such as Azdel from GE Plastics or Exxon's Taffen), polypropylene is the resin currently used in the CPI process. But Ron Hawley, v.p. of engineering, envisions that nylon or other engineering resins will become a key factor in the future development of this technology. He also says the process can accept up to 30% post-consumer or post-industrial recycled resin. In some applications the recycled resin serves to replace mineral fillers.

ADVANTAGES OVER GMT SHEET

Hawley says the CPI process offers several advantages over GMT sheet, including ability to mold more complex parts. Superior flow inside the mold results in more uniform distribution of fibers and eliminates resin-rich areas in complex parts. Hawley also claims substantial scrap reduction and the ability to reuse scrap material, much as in an injection molding operation.

The inherent cost advantages over GMT, resulting from scrap reduction and the elimination of the value-added step of sheet preparation, will be a determining driver for future applications and licensees, Hawley notes.

"As the parts become larger, our cost advantages become greater," he says. Typical part-size range for the CPI process is 3 to 20 lb. The process generally offers an output capacity of 300 to 1200 lb/hr.

AN INTEGRATED PROCESS

CPI's molding technology originated in a development project that began in 1989. In 1991, CPI established a strategic partnership with Neste OY of Finland. Neste assumed partial ownership of CPI, provided the necessary linkage for CPI to offer its technology to potential licensees in Europe, and became a primary resin supplier to European licensees, of which there is one at present.

The company declines to offer more than a general overview of the process. The two most proprietary aspects involve the extrusion compounding system and the preform accumulator. The compounding system uses a single-screw extruder built to CPI's proprietary specifications by HPM Corp., Mount Gilead, Ohio. The preform accumulator is designed and built by CPI. The control package involves a variety of dedicated microprocessor-driven software systems and monitors, which offer job/recipe storage and SPC capabilities. A more basic, lower-end control system also is available.

The CPI process begins with resin pellets being drawn from a gaylord or storage silo into a resin dryer. Hawley says each licensee has different requirements for material handling, storage and drying, and systems are tailored accordingly.

The dried pellets are metered together with long glass fibers and chemical additives by separate gravimetric feeders into the extrusion compounding system. "We worked with the feeder manufacturer to come up with a special design to accommodate the long fibers," says Hawley.

CPI's proprietary compounding expertise is said to disperse the fibers in a way that maintains the fiber length. CPI typically uses chopped fibers 1/2-in. to over 1-in. long that are supplied by Vetrotex CertainTeed Corp., Valley Forge, Pa., and Owens-Corning Fiberglas Corp., Toledo, Ohio. The fibers incorporate a special sizing chemistry specified by CPI.

The compounded material is extruded and collected in a heated chamber called the preform accumulator. The accumulator produces a hot billet or extrudate of compounded material, precisely weighed to meet the part requirement. The billet then is loaded into the bottom cavity half of a compression mold--typically by robotic means. High-speed compression molding technology takes over from there. For its own internal production operations, CPI uses presses of 1000-2000 tons with a max. platen size of 84 x 12 in.

COMMERCIAL APPLICATIONS

CPI's own applications list currently features the cab-back panel for the 1994 Dodge Ram T-300 pickup truck. This 10-lb part measures 66 x 32 in. It extends between the cab B-pillars and includes molded-in fabric. In addition, CPI is now ramping up part and mold designs for new automotive applications on 1995, 1996, and 1997 vehicles. These parts include an integrated front-end system for an unnamed car builder, as well as various components for recreational vehicles. Other non-automotive applications include the blower housing for Speed Queen commercial and industrial dryers.

Besides its own parts-making operations, CPI recently licensed its processing technology to two U.S. companies that supply parts to the automotive industry: MTD Products in Cleveland and Autostyle Plastics Inc., a unit of Masco in Grand Rapids, Mich. CPI delivered systems to both firms during the first quarter of 1994.

A third system is being installed at an unnamed European auto maker's captive operation. Slated to be on line in the second half of this year, this will be the largest system installed thus far, having four gravimetric feeders and an output of 1600-1800 lb/hr.

Hawley declines to discuss the financial or contractual terms of the licenses, which involve technology-transfer fees and a royalty schedule based on annual poundage throughput. He does say CPI is "very selective" in its choice of licensees. The license defines a particular region, industry, and application in which the licensee can utilize the process technology. CPI serves as the system integrator and turnkey supplier, and provides a full range of technical service, training, and support. In one licensing arrangement, CPI provided a full-time, on-site technical consultant for six months.

MTD and Autostyle are planning to use the CPI process to replace an existing GMT application for 1998 automotive platforms. MTD will mold a load-floor assembly; Autostyle will produce bumper beams.