Neue Entwicklungen zur Verbesserung der Pulverlackapplikation und -rückgewinnung: Abstract

Recovery and reuse of the powder that has not been deposited on the workpieces during application represents an important benefit of the powder coating technology. However, a characte-ristic concomitant phenomenon of the powder recycling process is the shift in the particle size distribution of the powder. Well known consquences are, among other things, a gradual decrease of the film thickness, an increasing agglomeration of the fines in the recycled powder, and sticking of the powder to the interior surfaces of the feeding system. On the other hand, the requirements regarding the quality and reliability performance of powder coating lines are increasing. Thus, there has been a strong need to execute investigations with regard to a better control of the complete powder recycling process. In this regard, with Fraunhofer IPA responsible, several R&D projects funded by the German governement and coordinated by the DFO have been carried out. The objective of these projects has been a wider application of the powder coating technology. Within the scope of these projects, the Fraunhofer IPA has build up a variable powder coating test line and has developed new sophisticated methods for measuring, controlling and simulating the powder coating process. By using these methods, the strong influence of the powder application parameters, especially of the spray guns themselves, on the powder recycling process has been demonstrated. The well known flat spray and conical spray nozzles show, as a consequence of their strong particle size separation, a rather critical behaviour. The lecture presents examples for the application of these new methods in order to improve the powder paint application and recovery process, e.g. the development of new powder spray guns with minimized particle size separation, enabling a consistent powder recycling process, the application of powder coatings with reduced content of fines, the development of conceptions for the future design of automatically controlled powder coating processes, and the design and optimization of today`s powder coating lines