For most people, silence is golden. But for Nidec America Corp., silence is gray and comes in the form of a computer-cooling fan. When the company needed a strong polymer to develop a cooling fan housing for a server application, engineers desired a cost-effective polymer with good structural integrity that would absorb noise and come in a custom gray color. Nidec partnered with LATI USA Inc., a developer of polymers for molding applications, to find the right polymer for the 5-inch fan housing.
Originally, Nidec considered nylon, polypropylene and PBT (polybutylene terephthalate), all 30 percent glass-filled. Engineers tested all three, ruling out nylon because it failed to hold up in sound absorption tests, and it compromised the integrity of the metal insert that they wanted to build into the housing. Eventually, the company decided to go with an integral plastic-bearing tower instead of the originally planned brass-bearing tower that required ultrasonic welding.
Consequently engineers re-focused on polypropylene, and PBT, which underwent numerous tests. The prototypes were evaluated in a hemi-anechoic sound chamber at a test facility in Torrington. Nidec engineers measured sound power and pressure levels, life, reliability, shock, vibration, and airflow characteristics. "Our tests concluded that PBT was slightly better than polypropylene," says John Hoover, director of engineering for Nidec. "We had great expectations for polypropylene. Generally, it has very good sound deadening characteristics and tends to absorb noise and vibrations. But the PBT, because of its higher density, proved to be superior."
Nidec developed the fan's impeller out of LATI's Latilon (polycarbonate) material grade 30D G/1O VO, which provides good mechanical characteristics and excellent toughness and dimensional stability. The fan housing incorporates the necessary strength of LATI's Later 4 G/30 VO PBT material grade, which Nidec needed for high impact resistance, strong rigidity, and superior sound absorption.
"Computer users are very concerned with the noise their computers emit," Hoover explains. "We first developed our quiet fan, called the Nidec TA500, for large computer room servers. However, due to the success of creating a low-noise cooling fan, we are now developing a series of TA500 fans for personal computers. In very quiet conditions such as office environments with numerous computers running simultaneously, a noisy computer can be disturbing. Plus, a quiet computer is an added selling benefit for our client."
Nidec's customer was very particular about the color of the fan housing. It had to exactly match their computer's gray color. "They didn't want any variation in color," says Hoover. "Using a one-source supplier like LATI USA provided us with a color consistency. Using different suppliers can result in variations of color as well as in processability."
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