Production of ADB optics Turnkey systems for LSR optics of LED headlights

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A collaboration between Elmet and Dow resulted in an innovative manufacturing technology for the main optics of LED headlights with Adaptive Driving Beam (ADB) functionality. To this end, Elmet's high-precision Smartmix Top 7000P dosing system has been combined with the Smartshot E cold runner system for consistently high-quality parts.

Working hand in hand with Dow, Elmet has fine-tuned the manufacturing technology for the main optics of LED headlights with ADB (Adaptive Driving Beam) functionality to suit it for use with a grade of LSR specifically developed for optical applications. Consistently high part quality is ensured by a combination of Elmet’s high-precision Smartmix Top 7000P dosing system with the mould’s Smartshot E cold runner system, in which the needle is positioned servo-electrically when the nozzles open and close.

The company helps to bring such projects to successful fruition by developing turnkey systems, drawing on its wide-ranging LSR expertise to ensure efficient material selection, its own mould-making facilities using proprietary cold runner and dosing systems and its many years of experience in optimising and automating injection moulding processes. Development times are kept short by simulation of the flow processes for mold cavity filling.

The Smartmix TOP 7000P dosing system is the first commercially available dosing pump designed to be FDA-compliant, which ideally suits it to high-purity optical LSR grades. The volumetric meter’s high measuring accuracy of 0.0156 ml per count pulse ensures high mixing quality and thus process consistency. Virtually abrasion-free delivery also rules out any contamination of the LSR by abraded metal from the pump which would impair functionality.

The company’s Smartshot E valve gate cold runner system has a compact servomotor for moving and positioning the nozzle needle for precise control of sprueless cavity filling. As a result, needle opening can be set in the µm range and the injection process can be much better balanced than is possible with stepper motor drives. And thanks to Elmet’s ability to ensure mold gaps of less than 10 µm, no flash is formed on the optical components despite the material’s very low viscosity.

The result of the current collaboration with Dow is a turnkey system for manufacturing ADB multiple light guide lenses from the optical LSR grade Silastic MS-5002. Elmet’s contribution included designing the sophisticated mould for injection moulding the geometrically highly complex parts. The part’s volume is around 35 cm³, corresponding to a weight of approx. 37.5 g, based on the LSR’s specific density of 1.07 g/cm³. Together with the widely varying, sometimes large cross-sections, this results in challenging cycle times for LSR mass production.

Elmet has tailored the mould’s cold runners to the selected LSR grade’s viscosity and thus flow behaviour, ensuring maximum process stability and providing uniform cooling. The mould inserts, made from a special steel alloy, were heat-treated and polished, which means that the mold surface is perfectly transferred onto the surface of the LSR part, making it possible to meet stringent optical industry requirements for both the light guides and the outcoupling sections of the lens.

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