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KUKA / Case Studies Industrial

Jun 29, 2020 — What started with a vision – eyeglasses as an accessory – back in 1964 has since grown into the world’s leading brand of lightweight glasses with sales in excess of € 100 million: “Silhouette”.

The KUKA KR5 Arc feeds in the blanks for the glasses with precision © Kuka

Silhouette is the brand name of the lightest glasses in the world, manufactured with painstaking detail and an individual design language. They are made in Austria using the best materials and latest technologies by a workforce numbering more than 800 people, and exported all over the world (export quota 95 percent). Since 2013, a KUKA KR 5 arc robot has been a firm feature of the production process at Silhouette.

A clear vision of what matters

Silhouette has stood for technical perfection and innovative design for 50 years. These are eyeglasses without frames, screws and hinges, combining functional and esthetic appeal with vision. Right from the beginning, the product range has been characterized by a consistent approach to paring things down to the essentials. Silhouette glasses have been launched into space more than 35 times on board NASA missions, and they are also worn by the Vienna Philharmonic Orchestra on its world tours as well as by a host of prominent celebrities, businesspeople and politicians.

The effects of wear over time combined with increasing maintenance costs of the facility prompted Silhouette to rethink its own production process in 2011. According to the Linz-based glasses producer, there are no fully automatic production systems available on the market able to handle the complete manufacturing process end-to-end; as a result, the existing equipment would have to undergo a complete overhaul. The project was taken on by Siemens and KUKA. It was possible to start operation after a conversion period lasting only four months. Since then, the system has been running smoothly in three-shift working.

The solution in detail

High-quality Silhouette sunglasses are made in a manufacturing process that is first-class throughout. The polycarbonate glasses are cut precisely to shape using the modernized multiple-spindle production system in which a KR 5 arc ensures that the blanks are fed in with the necessary precision. The KUKA robot uses its vacuum grippers to take the allocated eyeglass blanks out of the stacking magazines, places them in a centering station where they are exactly positioned and transfers them to the milling machine. This mills and drills the contours of the polycarbonate glasses in several steps. In this process, the multiplespindle center is capable of achieving tolerances of ± 0.015 mm and surface qualities with an average surface roughness of Ra = 0.1 μm. At the end of the machining process, vacuum grippers come into play again, placing the completed glasses into transport boxes. The KR 5 arc makes it possible to run a fully automated night shift thanks to its great flexibility, reliability and extreme degrees of freedom.

The robot and the machine tool are controlled using a centralized, high-end CNC, a Sinumerik 840D sl. This was extremely important for Silhouette, because although the machining technicians know precisely how to operate the machine tools, they are not familiar with handling a multiple-axis jointed-arm robot. The Siemens RunMyRobot software interface meant that these inhibitions could be dispensed with.

From today’s perspective, it is apparent that the investment has proven to be extremely sensible because of significant advantages in terms of productivity, reliability and user-friendliness. As a result, Silhouette, with KUKA and the mxAutomation software interface, always succeeds in producing optically correct lenses – 20 percent faster than before the system was renewed. “mxAutomation allows the KUKA robot to be programmed in the familiar environment of the machine tool – that saves long familiarization periods and helps overcome any initial reservations associated with robots,” says Joachim Strobel of KUKA Roboter GmbH.

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