Jeep Injection

Automotive Manufacturing & Production,  Jan, 2000  by Jeff Sabatini

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In 1997 the former-Chrysler Corp. introduced the world to what was initially known as the "China Concept Vehicle" (CCV), a small "developing market" car with an injection-molded composite body. This was the result of an initiative to design a vehicle for sale in China that was, among other things, simple and inexpensive to manufacture. Although the business case could never be made for production of the CCV (later re-named Composite Concept Vehicle), the technology made a case of its own. Enough so that in November, 1999, DaimlerChrysler supplier Husky Injection Molding Systems (Bolton, Ontario, Canada) opened its Detroit Technical Center in Novi, MI.

The showpiece of the new facility is what's said to be the world's largest dual-platen injection molding machine. This machine weighs 650 tons, has a clamping force of 8,800 tons and can inject more than 100 pounds of thermoplastic at a time. The reason for this enormity is that, apparently, DCX hasn't entirely given up on the CCV idea. For the time being, however, the only likely automotive production piece to come out of Husky's new machine is a thermoplastic hardtop for the Jeep Wrangler.

Husky is initially building hardtop prototypes for testing on DCX fleet vehicles. If things go as planned, the thermoplastic hardtop may go into full production (up to 5,000 units) as soon as October 2000. There are several advantages of a thermoplastic hardtop (as opposed to the current sheet molded composite (SMC) one):

* Weight. The thermoplastic hardtop weighs only 47 lbs., rather than 70 for the SMC.

* Speed and cost. DCX claims that thermoplastic hardtops can be produced 30% faster and carry a 10% cost savings.

* Simplicity. SMC hardtops are made from five pieces, while thermoplastic hardtops need just two. Furthermore, thermoplastic requires no trimming, meaning that no waste is produced.

* Environment. Since the thermoplastic has molded-in color, there are no emissions from painting. Thermoplastics are fully recyclable, and new hardtops could be made from up to 25% recycled material.

Of course, 5,000 Wrangler hardtops is a far cry from an entire car. But they would go a long way toward meeting some of the technical challenges that need to be overcome before an injection-molded car becomes a reality. The Detroit Technical Center will give DCX and supplier partners Husky, Decoma International Inc. (Concord, Ontario, Canada), Montell USA Inc. (Wilmington, DE), TiconaGmbH (Frankfurt, Germany), Progressive Tool & Industries (Southfield, MI), Ashland Chemical (Dublin, OH), and Paragon Die & Engineering Co. (Grand Rapids, MI),a venue to test technology, as well as prove production methods. Larry Oswald, director, Liberty and Technical Affairs, DaimlerChrysler, describes some of the issues they will be working on as DCX continues to develop this injection molding process:

* Materials and price. An ideal material would have great structural rigidity, tensile strength, and impact resistance across a broad range of temperatures. Both PET (polyethylene terephthalate, used for the original CCV) and PP/PS (polypropylene/polystyrene), when processed with short fiber additives, have potential. PET is easier to finish, while PP/PS is more easily processed. However, neither can yet be obtained for the "magic" price of $1.25/lb. that Oswald deems necessary for thermoplastics to compete with steel as a body material.

* Finish quality. No sure way to achieve a "Class A" finish with thermoplastics has yet been devised. Oswald thinks that the solution to this issue lies in in-mold clear-coating.

* Accuracy and repeatability. The goal here is to achieve a variance in dimensional repeatability of no more than 0.5 rum. The team is officially "close" to this mark.

* Prototyping. While a production thermoplastic car would be expected to achieve a 70% savings in tooling cost over a sheet-metal bodied car, there is still the problem of prototype tooling, which is expensive. Oswald indicates that prototype dies made from aluminum or fiber-reinforced epoxy fitted to a standard die base may be the solution here.

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