Grille guard garners top automotive accolade

May 10, 2007
A radical technique that insert-molds a 1.5-in.-diameter chrome tube inside glass-filled polypropylene (PP) gave a brush grille guard for GM SUVs and trucks the top automotive prize in an annual plastic parts competition.

The contest took place during the Innovations Conference sponsored by Alliance of Plastics Processors (APP), Washington D.C.

The molder, Composites Products Inc., Winona, Minn., says this is the first time an automotive OEM opted for an insert molding of this type and size. Traditional guards are built either by welding an assortment of tubes followed by a powder coat; or by cutting, bending, and either welding or mechanically fastening a tube assembly to a steel substructure that is then covered with a rubber bumper or plastic beauty cover.

In contrast, the insert-molded grille uses a PP composite made by the direct in-line long-fiber-reinforced (DLFT) process and transfer-compression molding. Cycle times for this single-step-operation are about 2 min, compared to hours for traditional methods. And the PP composite part is half the cost of rubber bumpers or plastic covers.

DLFT, transfer compression molding, and the customized PP let designers at Algonquin Automotive, Huntsville, Ont., strengthen the grille, especially at attachment points under the front bumper. The reinforced PP handles large cantilevered loads and its easy flow properties let designers add underside ribs for stiffness, so grilles don't deflect or vibrate much during normal driving.

Tooling was also key. The P-20 steel mold from Delta Mold Inc., Charlotte, N.C., was designed to protect the chrome from scratches. Tolerances of the tube and the mold were critical, says Delta Mold. Tube dimensional tolerances are roughly 5 mm (0.2 in.), while tool tolerance is essentially zero. Coupling the tube to the mold was also a challenge. Special details at the shut off areas and a custom tube clamp were needed to keep the PP from flashing.


A washer-door trim piece and a dryer door for Whirlpool tied for top Appliance honors. Minco Tool and Mold Inc., Dayton, Ohio, says the washer-door trim ring is the largest in-mold decorated part on the market in both size and production volume.

The in-mold decoration on the 33% glass-filled nylon lets Whirlpool differentiate products lines based on color, texture, and decoration. The technique for decorating also let designers apply a protective coating (liquid tape) so ring surface finishes aren't damaged during forming, adhesive application and cure, molding, shipping, assembly, or final installation. The nylon ring handles temperatures from –30 to 140°F.

A dryer-door window from Bemis Mfg. Contract Co., Sheboygan Falls, Wis., also took the Conference award. The two-shot injection-molded door is made from high-impact and chemical-resistant ABS/copolyester and ABS resins. They give the front of the dryer the look of glass to match the aesthetics of the washer lid and let consumers look inside. Bemis used a two-barrel molding machine and six axis-articulating robot to move the first part shot into the second cavity for overmolding in one cycle. Staggering the first and second shots lets the part mold with less molding pressure (i.e., a lower-tonnage machine).

Bemis also took the Transportation award for a John Deere 7000 Series engine enclosure. The hood assembly (hood, sides, and grill frame) uses over 90 lb of engineering resin (high-impact, heat-resistant PC/PBT) and is mechanically fastened together. The top and side panels are coinjection molded with a regrind core to keep down cost and boost impact strength. The assembly, when stripped of all metal fasteners, will be completely recycled after its useful life.

The Retail and consumer prize went to a multifunction chair from Sauder Manufacturing Design Group, Archbold, Ohio. It also garnered the People's choice award. The Trey chair took two years to develop, during which time designers revisited college to see how students engage their educational environment. In three quick steps the chair transforms into a floor rocker and table/stool, so students can sit in a variety of positions. Fort Wayne Plastics, Fort Wayne, Ind., used structural web gas-assist to mold parts from a variety of engineering resins (PP, ABS, glass-filled and unreinforced nylon, and TPE). Its use on the mission-critical frame and tabletop components let designers incorporate large structural rockers. It also lets the seat and frame back be consolidated into one part that passes stringent BIFMA test requirements. In addition, the process substantially reduces part weight and production cycles by hollowing thick sections.

A grip/seat base assembly molded by Innovative Injection Technologies Inc., West Des Moines, Iowa, took top Recreation and Leisure honors. The assembly is molded from PP and ABS resins and goes on a variety of Kawasaki personal watercrafts that hold three riders. Gas-assist and traditional injection molding build a beefy, yet 10% lighter assembly that meets or exceeds a 400-lb safety pull test.

Topping the list in the Medical and Scientific category was an electrosurgery cart for Megadyne Medical Products Inc., Draper, Utah. The cart was molded from a PP resin using gas counterpressure structural foam by FM Corp., Rogers, Ark. It replaces a painted MDF (medium-density fiberboard) part. Gas counterpressure structural-foam molding provides better aesthetics with no need for secondary finishing. It also let FM mold a more rigid part with thick rib sections and no sink marks. And the PP resin stands up well against hospital-grade cleaners.

A 36 × 58-in. plastic dumpster lid from Technology Plastics Inc., Bryan, Tex., earned the Industrial/Military award. A proprietary foaming agent from Phoenix Plastics, Conroe, Tex., and a few other additives make it possible (for the first time) to compression-mold a blend of recycled rubber-tire crumb and PE.

APP member judges handed out their award to an appliance handle from Bulk Molding Compounds Inc., West Chicago, Ill. A gas-evacuation technique (GET) was used to mold the handle from a bulk-molding compound (BMC). GET is a thermoset injection-molding method that uses a polyester-based BMC and pressurized gas. While gas assist has been around for decades, this technique has not been used with thermosets until now. The GET process and the polyester-based BMC chemistry let designers spec thick-wall sections and hollows parts to halve part weights and cure times.

Algonquin Automotive, (705) 789-3313,
Alliance of Plastics Processors, a business unit of the Society of the Plastics Industry Inc., (202) 974-5233,
Bemis Mfg Contract Co., (920) 467-8866,
Bulk Molding Compounds Inc., (630) 377-1065,
Composite Products Inc., (507) 452-2881,
Delta Mold Inc., (704) 588-6600,
FM Corp., (479) 621-4631,
Fort Wayne Plastics, (800) 335-5935,
Innovative Injection Technologies Inc., (515) 225-6707
Megadyne Medical Products Inc., (801) 576-9669,
Minco Tool and Mold Inc., (937) 890-7905,
Phoenix Plastics Co. Inc., (936) 760-2311,
Sauder Manufacturing Design Group, (419) 445-7670,
Technology Plastics Inc., (979) 822-7998,

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