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Fan-cooled headlights impose a new set of property demands.

As LEDs are used increasingly for car headlamps they have created a new vehicle component: the headlamp fan. LEDs enable more variations in headlamp design, they are long lasting, and they use less power than a conventional headlamp bulb, so saving fuel. But their high light output from a small chip means they run hotter than a conventional lamp, and so need cooling.

Cooling can be passive, using a heat sink, or active with a fan that can be mounted in the headlamp itself. The fans have to withstand under-bonnet temperatures and vibration, and when mounted in the headlamp, must not cause problems with light output. A bonus of installing cooling fans is that in the winter the fans assist headlight defrosting--LEDs emit a cold light unlike the hot light of xenon bulbs.

Hella developed LED headlights which are used for the high-low beam and daytime running lights of the Cadillac Escalade Platinum model. The fan was produced by EBM-PABST in Germany and uses DSM's newly developed Arnite PET XL which exhibits extremely low outgassing. The material also had to meet specifications for stiffness, strength, density and low war-page, and next to the material's outgassing properties, another key consideration was material cost.

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In contrast to conventional PBT, says DSM, the Arnite PET meets all dynamic requirements of the fans. And in comparison with PPA, its lower moisture absorption improved dimensional stability while also minimising warpage and weight of the parts.This allowed the fans' dynamic performance to optimised and also improved their balance properties.

www.dsm.com

www.ebmpapst.com/en
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Title Annotation:design
Comment:Fan-cooled headlights impose a new set of property demands.(design)
Publication:British Plastics & Rubber
Date:Feb 1, 2009
Words:265
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