Advanced LED chips with increased light output, can now be used for automotive headlamps. Because of their long service life and compact size, LED lamps have become an attractive alternative to gas discharge lamps. Big advantages are the high endurance and new design possibilities. In addition, their high efficiency saves energy and and thus fuel. However, since the active chip surface is rather small, it requires adequate cooling. Fans optimized to the special needs of automotive headlamps deliver the required air flow for active cooling. In all this, high reliability and long life are indispensible for all headlamp components.

For these reasons, premium automotive manufacturer Cadillac relies on Full-LED headlamps developed by Hella for the High-low beam and daytime running lights (DRL) of its Escalade Platinum model.

In the development of the fans for these new headlamp units, fan specialist EBM-PAPST from St. Georgen in the Black Forest (Germany) consulted the experts at DSM Engineering Plastics for identifying suitable materials with optimized outgassing properties for this application. The collaboration resulted in a completely new cooling air supply concept, molded in DSM’s newly developed Arnite® PET XL which exhibits extremely low outgassing.

Demanding Material Requirements
All automotive components are subject to permanent vibration and positive as well as negative acceleration, caused by e.g. bad road conditions and potholes. Furthermore, in the environment of the engine compartment, the fans operate in a very wide temperature range. As usual, the fan components are injection molded.

The specially developed Arnite PET was selected in order to eliminate outgassing problems. Richard Frissen, Business Development Manager Automotive Lighting at DSM, supported the EBM-PAPST development team in meeting the complex design challenges. The material requirements for the new application resulted in clear property specifications with particular regard to stiffness, strength, density and low warpage behaviour. Next to the material’s outgassing properties, another key consideration was material costs.

Arnite PET XL was tailored to this application. In contrast to conventional PBT, it meets all dynamic requirements of the fans. In comparison with PPA, its lower moisture absorption significantly improved the dimensional stability while also minimizing the warpage and weight of the parts. This facilitated the optimization of the fans’ dynamic performance and also improved their balance properties.

Altogether, Arnite PET XL met the specifications profile best. The thermoplastic polyester material therefore received approval from EBM-PAPST and Hella as the material for series production of the headlamp fans.

“The collaboration with the research group at EBM-PAPST from the very start of the project was the right strategy for success,” says Thomas Pusch, Sales Engineer for DSM Engineering Plastics. “It made sure that the optimum play of the rotor and stator will not be compromised even by high temperature fluctuation, by hardest impact when driving, or by humidity.”

The close collaboration between DSM and EBM-PAPST has also opened many new possibilities for substituting glass filled PPA or other high-temperature thermoplastic resins by Arnite PET XL in headlamp components. The outgassing performance, dimensional stability and stiffness of the material as well as its outstanding dynamic fatigue resistance made it the preferred choice for this innovation.

Due to the early involvement of DSM’s specialists and their expertise in material selection, mold design and processing, the project was completed within an optimum development time, fully meeting all specifications and resulting in a cost-efficient solution to the state of the art.