Oct 31 2005
The hardening of paint with UV light is uncharted territory for the automotive industry. This situation may soon change: Engineers need no longer puzzle out the optimum positions of UV lamps in a test facility, but can simulate it quickly and easily on a computer.
Road chippings, car-wash brushes, hailstones, garden shrubs – all these things can scratch the paintwork on a car. To enable the paint to withstand such small “collisions” without damage, more and more car manufacturers are now hardening the protective coating with UV light. In the paint shop, tiny particles of powdered paint flow through the air and come to rest on the car body, adhering only very lightly. Not until the powder has been melted in a heating zone – followed by irradiation with UV light – do the polymere molecules of the paint cross-link into a dense network. In this way they form an extremely hard, scratch-resistant coating. However, before the painting process can begin, the engineers first have to work out for each new car body in a test facility how many UV lamps need to be positioned at which points, and how they will have to move in order to harden all painted parts evenly. If the radiation is too strong the paint will become brittle, and if there is insufficient radiation the paint will remain too soft.
Researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart have joined forces with a car manufacturer to develop a simulation program that enables the optimum irradiation to be determined in advance on a computer. No test facility need to be constructed. “The simulation program called DLS-UV uses an algorithm that very quickly calculates the local distribution of radiation on the object,” explains Andreas Scheibe, a research associate at the IPA. The program enables engineers to interactively alter the robot and lamps’ movement. They can also select or enlarge individual sections of the car body and simulate the time-dependent irradiation with any UV lamps they choose, for the specified period of time. After only 30 minutes they know whether the chosen arrangement of the lamps is really the best, or whether they need to adjust it.
DLS-UV is embedded in the DLS program for visualizing dynamic coating processes, which allows engineers to optimize the preceding stage of paint application, too. “Expanding the DLS program to include modules that deal with light and radiation enabled us to complete the virtual process chain for painting 3D workpieces,” Scheibe is pleased to report. The new DLS-UV program is currently undergoing a test phase, and one car manufacturer is planning to adopt it in industrial series production by the end of this year.
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