Despite its stodgy image, materials technology can deliver a lot of punch and excitement to the more dynamic activity of manufacturing. It affects the stuff products are made of and how that stuff behaves-and costs-all along factory production lines, from stock receipt to product shipment. It's as basic as that.

Ever since that debut of Celluloid and other cellulose-based plastics in the late-19th century, and the invention of Bakelite early in the 20th, so-called "plastics" (a commercial word with no scientific definition) have been materials to be reckoned with.

Today, plastics are dominant in many applications and are challenging metals in many others, steel particularly. The issue is discussed and debated endlessly. One hopes that the arguers and the listeners, or at least some of them, soak up enough information to make proper and profitable decisions for their companies.

For examples, an article titled "The Image of Steel vs. Plastics" confronted readers of this magazine's June 1989 publication. And seminars on the question never seem to stop. PMA's forthcoming "Update on Composites," June 1990, is out ahead. It's preceded by a similar one in 1987, as well as many conferences sponsored by the Society of Manufacturing Engineers, Dearborn, MI: composites (plastics) on the program at Autocom '89 last June, "Tooling for Composites," also in June, and more recently, "Plastics Technology," held in late October.

Multiply this coverage by the number of other materials-oriented technical and industrial groups and discover how thoroughly the subject of plastics is covered.

In the next few pages, get the benefit of two industry experts as they write, respectively, about the forming, molding, or "stamping" (choose the word you like) of sheet-molding compounds made from, first, thermosetting resins, and second, thermoplastic resins. The first material can't be reheated and recast, the second kind can-probably an oversimplified explanation.

Readers whose companies form and fabricate sheetmetal will discover that, in several respects, the manufacturing techniques used for plastic materials and for their own stock-in-trade are similar. They may even conclude that plastics forming and fabricating may be a profitable adjunct to their manufacturing operations.

Molding Large Thermoset-Plastic Parts

Now in the final phase of a two-year program that combines highly technical and commonsense industrial engineering, Navistar's Columbus, OH, truck-parts plant can claim to have one of the country's most efficient facilities for compression molding of thermoset-type plastic sheet molding compound. The 300,000 sq. ft. plant, including a recent 50,000 sq. ft. addition, is the sole source of sheet-molding-compound (SMC) parts for the company's truck-assembly plants.

Hood assemblies, some weighing more than 125 lbs., are a major product, along with fender extensions, rocker panels, air deflectors, and a variety of other exterior parts. Navistar also contract-molds service parts for GM passenger cars. The plant expects to process about 17 million lbs. of SMC this year (1989).

That two-year program, involving $9.4 million of capital improvements, has three main goals: expansion of capacity, reduction of manufacturing costs, and improvement in just-in-time economics. The program's major projects include that 50,000 sq. ft. addition for presses, two large compression-molding machines, a quick mold-change (QMC) system, three automated parts-mover systems, a robotic paint line, and the relocation and redesign of second-operation work cells. The most spectacular new project is the transfer line. This is basically a plant within a plant and is separately funded. It molds and assemblies two series of Navistar's high volume hoods.

Top Goal: Cut Costs

According to Plant Manager Mark Skrzypek, the investment in the projects will pay off in several ways:

• Raise product throughout by 30 percent without adding manpower or in-process inventories.
• Increase inventory "turns"-a reflection of reduced work-in-process-from eight to nine per year to 35 to 40.
• Cut average flow-through time-the interval between molding startup and shipment of assemblies-from 15 days to five days or less, if necessary.
• Increase molding throughput about one third by installing a QMC system and introducing other efficiencies, including the removal of second operations from the press area.
• Reduce surface damage-and repair costs-to Class A surfaces by two thirds.

Molding Output Up 33 Percent

As part of the overall program, Skrzypek bought two Williams-White self-leveling compression presses, one rated 2500 tons, the other 3000 tons, for expansion purposes. They supplement the plant's nine presses previously purchased from the same firm and designed with clamp ratings that range from 500 to 2500 tons. Now there are four presses with capacities from 2500 to 3000 tons.

Beyond pure expansion, however, Navistar achieved a 30 percent increase in effective molding capacity through productivity gains in its existing press operations. These gains arise from the combined effect of other press room projects.