Engineers are looking for ways to boost value and gain business. One example comes from Mazda, which is leveraging a plastic foaming process developed at MIT. Mazda’s injection molding process cuts part weight 20 to 30 percent by mixing supercritical fluid with plastic resin, such as nylon, in the injection barrel. The SCF causes the melt to expand rapidly when injected into a mold, requiring less resin. After initial injection, the mold core is precisely retracted, creating an outer layer with microscopic bubbles that ensure each part has the necessary strength and rigidity. The size of the bubbles in the core layer are adjusted to reduce density as desired, thus allowing control of the resin savings. Mazda says the technique can be used on most plastic car parts, and will be introduced on 2011 models.Mazda’s initial announcement called the technology proprietary, and Mazda has in fact been awarded patents for the development. Mazda, however, neglected to mention that the microcellular foam technology was developed at MIT and licensed to a Massachusetts company called Trexel. More than 300 molding machines use the SCF technology. Eighty-five discrete components have already been developed for use in cars, Trexel President David Bernstein told me in a recent meeting in Woburn, MA. MuCell works best with semi-crystalline engineering resins.
Mazda apparently did develop the concept of using core-back or “expansion” molding with the process, a brilliant idea. Trexel and Engel will be showing their approach to core-back molding at the National Plastics Exposition in Chicago June 22-26.
I’ll be posting more ideas on microcellular foam here at www.designnews.com, and writing articles for the print edition as well. One big issue I’ll explore is how the microcellular foam process can improve component properties.
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