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Machine Design

Polymer thwarts assembly woes

Aluminum spacers used to mount interconnect devices posed assembly challenges for telecom equipment makers.

PEI spacers used in telecom devices provide heat resistance and electrical shielding to connected components. In contrast, the previous aluminum spacers were electrically conductive and transmitted heat to adjacent components.

Device performance hinged on accurate assembly alignment but even with locating holes, aluminum spacers could be misaligned when riveted into assemblies.

To simplify construction, designers at Minnesota Rubber/QMR Plastics, Minneapolis, devised a self-aligning spacer molded from a high-performance polyetherimide (PEI). Telecom assemblers can now quickly pressfit assemblies together and thus eliminate alignment issues and costly scrapped components.

The PEI spacers reportedly perform better, are more durable, cost less, and are 50% lighter than their aluminum counterparts. They are designed with 1/8-in. through holes on each end to accommodate wires that connect to other components.

PEI is an amphorous thermoplastic with excellent hydrolytic and UV stability as well as radiation resistance. With high strength and modulus, PEI has high heat resistance and can be used continuously at 375°F. Besides its use in telecom components, PEI is a candidate for applications seeing repeated steam, hot air, and cold chemical sterilization. The polymer can be unreinforced or reinforced with glass fiber and other materials including carbon and minerals.

Minnesota Rubber/QMR Plastics,
(952) 927-1400,

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