How to mold a prizewinner

June 2, 2005
Transparent motorcycle flyscreens and tank airbox covers raced away with the Recreation & Leisure honors at a recent structural plastics conference.

Transparent motorcycle flyscreens and tank airbox covers raced away with the Recreation & Leisure honors at a recent structural plastics conference.

Transparent parts for the 2005 Buell Lightning CityX motorcycles wowed judges at the Society of Plastics Industry conference. The Hero Blue Translucid tank airbox covers and flyscreens got top honors in the Recreation & Leisure category. The Structural Plastics Div. (SPD) contest recognizes innovative plastic parts that bear loads, provide support, or enclose a product. Bemis Manufacturing Co., Sheboygan Falls, Wis. (, molded the parts for Buell Motorcycle Co., East Troy, Wis. ( It is the first time the OEM used the transparent polycarbonate/polybutylene terephthalate (PC/PBT) polymer blend. The tinted transparent look gives the bike color, yet makes some mechanical parts visible underneath. The polymer blend's "see-through" styling helps attract younger riders to the street bikes while its good structural properties keep covers and windscreens stable at high speeds.
The fuel-module housing designed by Magneti Marelli Powertrain USA, Sanford, N.C. (, took the Judges' Award . It is lightweight yet rugged and lets Mercury Marine ( field a housing 35% lighter than the original while eliminating 31 fuel leak paths. The molder, Pyramid Plastics Inc., Rockford, Ill. (, used RJG decoupled molding to improve part quality. The added tooling complexity cut labor and defects to shave 13% from the housing cost. The tool also featured an innovative quick-connect fitting with a stepped parting line. This got rid of flash and mismatches at O-ring surfaces. The molded part makes for a more reliable assembly and eliminates the need for secondary machining to meet critical tolerance specs.
Mack Molding Co., Arlington, Vt. (, walked away with both SPD Conference and Medical/ Scientific honors. Mack used a three-prong approach to mold 20 parts for an automated external defibrillator. Gas-assist injection molding was used to fill out thick sections. Insert molding provides a watertight seal around a clear window in one of the colored parts. And multimaterial molding let Mack overmold polycarbonate substrates with impact-absorbing TPE (thermoplastic elastomer) and TPU ( thermoplastic polyurethane). Multimaterial molding also was used to add gaskets on defibrillator doors. The overmolded TPE and TPUs let the units take 1.5-m drops and withstand harsh conditions that often characterize emergency situations. The Zoll AED Pro from Zoll Medical, Chelmsford, Mass. (, is an automated external defibrillator (AED) that can also provide manual defibrillation with controlled access for advanced life support users.
Tupperware Corp., Hemmingway, S.C. (, took both the Retail/Consumer Products and People's Choice awards for the FlatOut! Collapsible Storage Container. The colorful, adjustable food containers rely on a simple geometric concept of opposing angles to stay open when expanded and closed when folded. Material selection was key. To mold the part in any Tupperware plant worldwide, the OEM chose two-component injection molding that combined polypropylene (PP) and a thermoplastic elastomer (TPE). The material combination makes the containers stiff when expanded, yet flexible enough to easily shift into fully open, fully closed, or an intermediate capacity.
The Citadel Liquid and Tomato Paste container designed and molded by Buckhorn Inc., Milford, Ohio (, is the first to combine structural foam molding, commodity resins (polypropylene and polyethylene), internal support structures, and hot-plate welding. It took the Industrial & Military award. The all-plastic collapsible containers replace rigid wood, corrugated, and metal products traditionally used for handling liquids. They can be stacked for up to 2 years at 150°F. Low-pressure structural foam molding was the process of choice for building the large structural parts from a 90-lb shot. Buckhorn devised a patentpending lid latch that does not protrude beyond the perimeter of the container and eliminates the need for metal banding. The company uses a tooling insert that converts container bases to accept a liner bag with an outlet valve that connects to a liquid-evacuation system.
The transportation award went to Innatech LLC, Rochester, Mich. (, for the first overmolded plastic to serve in a load-bearing trim piece. The parts attach to the top of the rear quarter panels on 2005 Mustang convertibles, tensioning the top to the body. Innatech used two-shot injection molding to overmold a thermoplasticvulcanizate (TPV) onto a 35% glass-reinforced nylon (PA66/6). The Zeotherm TPV from Zeon Chemicals L.P., Louisville, Ky. (, has a rubberlike appearance that closely matches the car's other weather and body seals. Weatherability of the TPV-to-PA bond was a key factor during the materials selection process. The materials underwent tough environmental testing including an 80°C xenon arctest to simulate intense UV exposure in the Southwest desert. The switch from a painted-steel part to the overmolded-TPV/PA helped drop part cost and shave its weight 24%.

An aluminum one-cavity mold from M.S.I., Cedar Rapids (, features creatively placed gates that help ensure the polyethylene entirely fillsout the deep-draw cavity during the low-pressure structural-foam molding process.

The portable Site Lock alarm systems feature built-in motion and vibration sensors as well sirens and strobes. A wireless receiver/transmitter monitors the various sensors using 900-MHz spread-spectrum communication at a range of 2,000 ft.

In the Building and Construction category, the judges honored both Horizon Plastics Co. Ltd., Cobourg, Ont. (, and The Minco Group, Dayton, Ohio ( The Half in Ground Junction Box from Horizon is molded using low-pressure structural foam. The hardest thing about the molding, says the company, was getting the entire tool to fill on the large, deepdraw part. This required crafty placement of gates. Molded-in feet were also added to help eliminate the need for pallets and simplify handling.

A collaborative design effort between The Minco Group and DeWalt was key in developing the Site Lock, a portable wirelessalarm system for construction sites. The unit's six parts are injection molded from recycled plastic — Cycoloy, a PC/ABS (polycarbonate/acrylonitrile butadiene styrene) blend and Lexan, a flame-retardant PC. The plastics were selected because they meet structural demands and stand up well to dust and grime on job sites. The base unit is a clamshell design that disassembles readily for battery installation and also makes the device easy to recycle.

The Lawn & Garden honor went to Buckhorn Inc. Its Everkote Armored Wood uses an eight-cavity, aluminum mold from Green Machine Tool Inc., Dayton, Ohio (, to encapsulate an engineered wood core with a polypropylene skin. The polymer gives the beams good UV resistance and can be nailed and accepts screws. It can be cut for use in fencing and structural cross members. A low-pressure structural-foam process was needed to push the large shot and to keep the wood core from shifting on the positioning pins inside the mold.

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