Anti-fog coating of headlamp lenses
Nowadays, all plastic headlamp lenses come with a protective coating. Thanks to the latest generation of robots, transparent micrometer-thin protective layers can be accurately applied under cleanroom conditions.
GfO (Gesellschaft für Oberflächentechnik AG) specializes in the technical and optical finishing of surfaces and in the coating of plastic moldings with metals, oxides and transparent lacquers. Approximately 75 percent of its customer base is in the automotive industry.
Almost all reputable OEMs and suppliers are currently exploiting the opportunities presented by Elamet and Sicralan, the coating processes developed by GfO, with new applications for plastic constantly being discovered. Weight savings, greater cost-efficiency and enhanced safety in the event of an accident as well as new freedoms in design are the main reasons for the growing use of composite materials in vehicle construction.
Robotic coating under cleanroom conditions
The extent to which GfO is not only driving forward the development of innovative coating technologies but also their industrial use is illustrated by a setup for the application of transparent anti-fog coatings on plastic headlamp lenses. The Sicralan AF coating is between 2 and 6 micrometers in thickness, depending on product variant. This protective layer reliably prevents condensation and the formation of water droplets on the inner surface of the lens. The coating process must take place under cleanroom conditions.
The GfO coating line comprises 2 Stäubli RX160 Paint robots operating in concert within a confined space. The headlamp lenses arrive via a transfer system. At a defined position, one of the two Paint robots picks up the component together with its receptacle from the transfer system and maneuvers it into a cleaning station. The second robot retrieves the now clean lens and guides it along a precisely defined path in front of a spray gun. The flow coating method has the great advantage that there is no overspray and the expensive lacquer can be applied without waste.
The RX160 Paint manipulates the lens in an intricate pattern. The precision with which the Stäubli robot works here produces a perfect coating result, which is all the more impressive considering that the thickness of the layer is no more than 6 micrometers.
When the coating process is complete, the robot parks the lens and leaves it to dry. It is subsequently retrieved by the handling robot and placed on the transfer belt for discharge from the system.
Process-reliable application in the μ range
Thanks to the use of robots, this part of the production line is maximally flexible and can cope with the 30 different lens variants without retooling. The features of Stäubli's six-axis industrial robots that are most appreciated at GfO are their enclosed design, which makes them suitable for cleanroom working, and the fact that their compactness in no way diminishes their impressive reach and load capacity. This allows the handling, precleaning and coating all to be performed in a relatively confined space. In addition, the outstanding path accuracy of the RX160 facilitates coating of reproducible quality in the μ range.
Due to the high demand for anti-fog coatings and to fill order books in the automotive sector, the plant is currently operating 3 shifts. The quality of the components reveals itself in continuous use. This is also an aspect in which the 2 Stäubli RX160 robots excel, with no breakdowns at the plant having occurred to date. Thanks to their positive experiences with the coating robots and the support provided by Stäubli Robotics Bayreuth, the senior management at GfO have stated their intention to give preference to Stäubli machines for future applications.