Automotive plastics

Plastics Engineering, Sept, 1998 by Victor Wigotsky

Heightened awareness

Don Vesey, supervisor, Composites, Plastics, and Textiles, at Chrysler Corp., characterizes the company's position on plastics as an evolving awareness of expanding opportunities in material selection. "The important thing is to learn to use any material most effectively; and that is what we try to do as the choices become greater Design, with maximum functionality and cost effectiveness, is the key, and plastics are a growing challenge as we get to know more about the materials." One major focus, among numerous others, is the development of molded-in color with high gloss, which could eliminate painting of large exterior panels.

Chrysler has had success in initial tests of its large-part plastic injection molding technology, exemplified in its recent PET-bodied prototypes. As a result, according to Larry Oswald, executive engineer, Advanced Body Engineering, plans are afoot "to continue the project on a larger basis with equipment designed to match Chrysler's specific requirements for large plastic automotive parts."

Husky Injection Molding Systems has purchased land in Novi, Mich., to build a 65,000 [ft.sup.2] test center that Chrysler will use when and if the company goes into production with the PET technology. The facility is expected to be operational by July 1999, two years ahead of schedule. Chrysler has already showcased the technology with its one-of-a-kind, hand-built, PET-based concept cars, including the initial Composite Concept Vehicle (CCV), and the subsequent Plymouth Pronto, Plymouth Pronto Spyder, and the Dodge Intrepid ESX2.

The test center will house the largest two-platen injection molding machine in the world, which will be able to apply 8800 tons of clamp force. It will be as large as a locomotive, and, together with the mold, will weigh as much as two fully loaded 747 airplanes. Though planning to work with other customers in addition to Chrysler, Husky says that the Chrysler project prompted the acceleration of the building plans.

The test center's equipment will permit molding of a four- to twelve-piece car body in plastic. By contrast, an equivalent steel-bodied car would require at least 80 to 90 parts. Oswald says that PET, commonly used to make beverage bottles, "is the first lightweight material we've developed that actually would cost less than traditional steel. The end result would be more efficient and affordable vehicles."

Modular thinking

Lear Corp. continues to focus on modularity and integration of design in its quest for further growth in the global automotive market. "Most of the company's recent product advancements," says Jim Masters, vice president, Advanced Technology, "reflect the basic philosophy that an integrated design, although inherently complex, may require only one part number, as compared with possibly hundreds of part numbers, to do the same job."

Lear's exhibit of new products at the 1998 SAE International Congress and Exhibition is representative of the company's commitment to modularity to improve functionality and productivity and to minimize costs. A front seating module, officially dubbed "The Revolution," is a fully tested system that integrates front-row seats with center consoles, safety belts, and side air bags. Standardized across many vehicle platforms, it is designed to be installed as a complete row, in a single-step operation. Assembly time at the vehicle plant is reduced, and structural redundancy of load paths within the vehicle is eliminated.

A common 10 inch wide die-cast magnesium backframe provides a standardized seating structure for all existing car platforms. (Engineered plastics could be an alternative to the magnesium.) But flexibility of design is not lost; molded, contoured seat backs and cushion components (called "halos") fit over the common frame. A polypropylene core with elastomer edging, the halo can be changed to meet specific seating preferences. Consumers will be able to choose the seat's shape, styling, fabric, and comfort level, and every halo that is tooled then becomes an addition to the OEM'S inventory for all vehicles.

The front-seating module, which meets standard government and OEM safety requirements, is built on a cross-car platform that becomes the system's structural bridge. A common platform and load path (the path the safety belt load takes in a crash) eliminates the need for repeated testing, tooling, and engineering, leaving only the costs for new halos and trim. The seat concept is now being adapted to existing load floor and lighting structures, with a view to further minimizing or eliminating structural redundancy Additionally, Lear's rear-seating module, including the seat back structure, integrates the rear package tray; audio speakers, a high-mounted stop lamp, wiring harness, trim, and head and belt restraints.

A "one-step" interior door module - as a front, rear or sliding door, hatchback or liftgate - also requires only a single part number. With all subsystems and components already mounted, it is quickly installed in the exterior door panel, simplifying one of the most time-consuming and error-prone jobs in the car-building process. Two United States and two European OEMs now are doing detailed application studies of the design.