When E-Z-Go, a division of Textron, selected custom molder GI Plastek (Newburyport, Mass., U.S.A.) to produce both the cowl and instrument panel for the E-Z-GO ST 4x4 Utility Vehicle, the challenge was to manufacture parts that achieved extremes of aesthetic and mechanical performance at reasonable cost. Marketed as a true off-road vehicle for rugged terrain, the utility vehicle demanded heavy-duty construction and superior corrosion protection. Equipped for 1,100-lb bed load capacity, the unit reportedly hauls more than any in its class, which demanded parts capable of optimum performance. Yet the vehicle required a Class A finish on the cowl and a unique texture in the complex dashboard, which contains all gauges, indicators and hand-operated controls, plus a passenger side storage compartment, two built-in cup holders, two-way radio/cell phone holder and CD player slot.
Anticipated annual production volumes of 2,000 to 3,000 units wouldn't support standard injection molding or compression molding, so GI Plastek used reaction injection molding (RIM) for its strengths in the area of reproducing both glossy and textured surfaces. RIM was ideal for in-mold coatings (eliminating post-mold painting) and nickel shell tooling (a 5 mm electroformed nickel shell backed with composite, over a steel framework) for the cowl, which could yield a highly polished mold surface, but at a 45 percent cost reduction compared to steel tooling.
For the cowl, a prepped and heated nickel mold (71°C to 82°C/160°F to 180°F) made by PPD Molds (Waterville, Quebec, Canada) is sprayed with "Recon" Green body color, applied via the company's proprietary Protek in-mold coating process, which creates a chemically crosslinked, UV-stable Class A automotive surface without the risk of orange peeling or running. When the coating is partially crosslinked, Bayflex 110-50, glass-reinforced (18 percent loading) elastomeric polyurethane material from Bayer Polymers LLC (Pittsburgh, Pa., U.S.A.) is injected. After injection the part is cured for 30 seconds at mold temperature. To make anticipated customer changes easier on the dashboard, GI Plastek uses a more expensive steel mold from Creative Mold Co. (Auburn, Maine, U.S.A.) with a chemically etched surface that creates the textured finish on the dashboard. A black Protex in-molding coating is applied and the same glass/Bayflex resin material is injected, with similar curing parameters.