Design News, January 2013

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Materials & Assembly The first consideration is often stiffness and impact at low and high temperatures when replacing metal, because these two properties are likely the reason metal was chosen in the first place. When replacing elastomeric materials, the considerations are durometer (hardness) and compression set. It's helpful to remember that on their own, plastics are not as rigid as most metals, but can nonetheless replace metals with the addition of ribs to the design or filler to the base resin without sacrificing performance levels, leading to an optimum strength-to-weight ratio. The next opportunity for replacement lies in conductivity for heat dissipation, as in the high-brightness LED example, as well as electromagnetic shielding (EMI/RFI). Thermally and electrically conductive polymer formulations can be tailored to specific applications, making them more cost effective than metal. Finally, the team of designers and material technologists considers aesthetics, magnetic properties, perceived quality, and density. As an example, OEMs are now turning to plastics with a metallic filler to create engine covers that improve aesthetics and perceived quality while removing paint, associated VOCs, and cost from the process. Again, to meet the specific targets in an application, a material supplier can customize each of these categories and can also combine them according to the application's needs. Using this approach offers an opportunity to significantly redesign components to utilize the polymer material to the fullest. This can involve functional integration, in which two or more components in an assembly are combined. Further, this approach can include designing for productivity improvements, whether by eliminating secondary operations, reducing wall thickness for faster cycle time, or lowering scrap rates. Finally, adding functionality is also possible with metal-toplastics redesign. DN Marc Mezailles is automotive market manager Europe for PolyOne Engineered Materials. For More Information: PolyOne Engineered Materials: Design News | jaNuary 2013 | www.d esign n –56–

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