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Encapsulation of Components by Reaction Injection Molding

September 24, 2012

The heart of Reaction Injection Molding (RIM) is versatility. Like its name implies, it is a reactive process. Using polyurethane or foamed polyurethane, the process reacts and adapts, filling an existing mold or encapsulating an existing component. To get an understanding of how it works, picture liquid plastic flowing throughout all the features in your mold, then solidifying.

Encapsulation is an invaluable process that opens up many previously unconsidered possibilities for new product designers. It can be used to encapsulate circuit boards, castings, machined parts and much more, enhancing their performance while minimizing costs.

A great example of the capabilities of RIM comes in the form of a 5 ft. long circuit board that we worked on. The company we worked with was manufacturing the boards for use in commercial air traffic control radar antennas. These antennas are constructed outdoors. Previous production attempts were very labor intensive, and did not give the boards consistently adequate protection from the elements.  As a result, the success of the entire project was in question.

What the customer desperately needed was a cost-effective material and manufacturing method that totally encapsulated the fragile circuitry, while remaining radar transparent. Using RIM and a high-density foam polyurethane manufactured by the Bayer Corporation, the encapsulation followed the shape of the board. The mold incorporated gussets and attachment bosses with protruding coaxial connectors. In this way the boards were protected, but could still interact with the systems they needed to.

RIM can handle intricate parts like the 5 ft. circuit board without a problem. When complete, RIM produces parts that are dimensionally stable, chemically resistant, physically tough, wear resistant and aesthetically pleasing. It’s an excellent option for large parts produced in short run or low volume production quantities.

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