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Process variety a hallmark of structural plastics

If you’ve attended or otherwise followed SPI’s Structural Plastics Div. (SPD) Conference & Design Competition the last few years, you know that the program has evolved into a showcase of plastics processing. Indeed, if you can imagine a combination of processes—gas assist with multimaterial, multiple elastomer overmolding—it’s probably been done with a part at the SPD conference.

This year was no different. Parts were made by standard injection molding, gas-assist molding, structural foam, coinjection, structural web, RIM, thermoplastic compression molding, rotational molding, and extrusion blowmolding. The most popular? More than 28 percent of the 57 parts were molded via structural foam; 21 percent were made via straight injection molding; 19 percent were molded via gas assist; and 10 percent used structural web.

As usual, a panel of judges reviewed the entries and picked the winners in a variety of categories. And while these winners are innovative and compelling, it’s easy to miss some of the more interesting—not necessarily award-winning—parts. Herewith, then, is a quick review of some parts that won, and one that’s just worth a second look.

  • Hammer handle (Figure 1). Possibly the most attractive part at the conference was the Robo Hammer, which features an injection molded, multimaterial, ergonomic handle. The handle is molded in three steps, as shown in the photo. The first molds the hard substrate; the second step overmolds an orange thermoplastic rubber; and the third step adds the gray TPR. All of this is intended to minimize shock to the hand. Molder Goshen Rubber Cos. (Englewood, OH) makes right- and left-hand versions in a two-cavity mold and uses extensive robotics for parts transfers. Award: Single part.

  • Lid console (Figure 2). This part used to be molded and painted, and then the warning label was glued on. Molder Camoplast Inc. (Richmond, PQ) eliminated the postmold operations by switching to inmold decorating and labeling. The metallic finish and safety warnings are applied on an ABS film substrate, which is thermoformed to shape and then inserted in the mold. Gas assist is used also to eliminate sinks around the hinge. Award: Recreation and leisure.

  • Adjustable fishing rod holder (Figure 3). The next time you take the boat out, consider taking along the Pro Series adjustable rod holder, molded by Attwood Corp. (Lowell, MI). It combines gas assist, plastic/metal composite molding, and a generous use of recycled material. The complete part is in the upper right-hand corner of the photo; other parts show the gas channels in cutaway views. Award: Environmental.

  • Soft-touch steering wheel (Figure 4). Molded by Bemis Contract Group (Sheboygan Falls, WI), this steering wheel is not revolutionary by design, but it is flexible. It consists of a metal insert and a glass-filled PP substrate overmolded with a modified PPO soft-touch material. By changing the metal insert and the color of the soft-touch material, Bemis can modify the steering wheel to accommodate different customers. It’s molded in a two-step process using a two-cavity mold—one for molding the substrate, one for the soft-touch material. A robot pulls and transfers all parts and places the metal insert. Award: Lawn and garden.

  • Work-site radio (Figure 5). Black & Decker struck a marketing nerve when it developed the Charger work-site radio. While the average lifespan of a radio in a construction area is only six months, the Charger is specifically designed for abusive environments and uses a gas-assist molded roll cage that protects the radio in drops up to 6 ft. The PP roll cage is lightweight, flexes on impact to cushion blows, and offers the strength and stiffness that comes with gas assist. Award: Consumer electronics.

  • Flower pot planter (Figure 6). This one got a lot of chuckles, and it didn’t win an award, but it’s worth a look all the same. Designed by a former helicopter pilot in New Hampshire, the Stand Up Garden is designed for people who garden year-round and like to take the plants inside in the winter. The green tub is highly engineered and designed to hold dirt for planting, a small pond if you like, and distributes water for irrigation. It’s molded in three parts via low-pressure structural foam by Horizon Plastics in Cobourg, ON.

    Next year’s SPD conference is April 1 to 3, 2001 at the Renaissance Waverly Hotel in Atlanta. Contact the SPI Structural Plastics Div. for more information.

    Contact information
    Society of the Plastics Industry
    Structural Plastics Div.
    Washington, DC
    Karen Miles
    Phone: (202) 974-5247
    Fax: (202) 296-7259

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