By: James Snodgrass
EUROPEAN PLASTICS NEWS
July 19, 2013
Engel Holding GmbH will demonstrate thick-wall optical molding at K 2013, showing how plastics can be used for lightweight car headlight lenses that are normally made from glass, writes European Plastics News technology editor James Snodgrass.
Weight loss is an obsession shared by all car manufacturers. During the last few decades the need to add safety protection to vehicles — pedestrian collision protection, side-impact reinforcements, anti-lock braking, crumple zones — and the increasingly high standards expected by regulators have had a huge effect on the curb weight of vehicles. Next, add to that the abundance of creature comforts from satellite navigation, in-car entertainment and electrically powered seating.
Take a base model Volkswagen Golf, for example. In 1974 its curb weight was 1,740 pounds. Skip forward 30 years and the base Mk V Volkswagen Golf weighed 2,916 pounds.
In recent years, however, emissions and fuel economy have become the biggest concerns for automobile manufacturers. Cars needed to be safe and secure, but they also needed to be greener. To achieve that, all cars had to go on a diet, and that diet has seen results. By comparison, today's base model MK VII Volkswagen Golf weighs just 2,315 pounds, despite being considerable longer, taller and wider than the 1974 original, while also being safer and better equipped.
Plastic components are often used to replace metal parts to reduce weight. And now plastics are starting to replace glass elements. At K 2013, Engel will be demonstrating — along with its partners, material supplier Bayer AG and mold-maker and production consultant Krallmann Gruppe — a light-emitting-diode collimator lens for automotive headlamps injection molded from polymethyl methacrylate.
A collimator lens is used for narrowing, or focusing, a light source. For some years, particularly in the premium sector, arrays of LED lights have been used in place of more traditional and power-hungry halogen or xenon bulbs. The LED arrays are focused through a collimator lens to provide a single, powerful beam. These lenses would ordinarily be made from glass.
Plastics offer a number of advantages over glass optical components, other than simply being lightweight. Polymer lenses can be produced more cost effectively and offer greater scope in terms of product design.
At the company's pre-K press conference at its headquarters in Schwertberg, Austria, Engel's head of R&D, Georg Steinbichler, explained the problem of making injection molded lenses for automotive use: "Lenses of a headlight have a thickness of up to 30 millimeters [about 1.2 inches], which presents new challenges for injection molders."
Steinbichler continued: "We have worked on an LED collimator lens for automotive headlamps. It is a high-precision part with 15mm thickness and we've managed to achieve drastic cycle-time reduction with the application of advanced multilayer technology."
The 15mm part isn't a mere technology demonstrator but an actual part of a forthcoming motor vehicle.
"We can't tell you who, but one of the manufacturers is launching a car in the next few weeks with a thick-walled lens made using our multilayer technique," said Steinbichler.
The demonstration at K will show an Engel e-motion 200/110 T machine with integrated Engel viper 12 robot. This will produce a pre-molded part in a mold supplied by Krallman. The part will then be recoated with further layers of the same material in subsequent steps. Engel claims the multistage process improves upon a single-layer process because recoating removes sink marks, thus improving optical quality.
The process that will be demonstrated at K 2013 requires just one injection unit instead of two, improving cost efficiency.