The electrostatic spray painting process with high-speed rotary bell atomizers

The present contribution summarises ongoing investigations of the Fraunhofer-Institute for Manufacturing Engineering and Automation aiming to extend the range of applicability of numerical simulations applied to the electrostatically supported painting process with high-speed rotary bells. Mainly two aspects are considered: - Sensitivity of the simulations to parameter variations as used in the practical application - Interaction of the electrical and the spray flow field wiht different work piece geometries In the first case, a design of experiments (DOE) was performed, including all relevant operating conditions changing the properties of the spray cone and thereby the film thickness profile. In total, 32 individual conditions were experimentally investigated and simulated. Finally, some characteristic numbers have been compared, e.g. the width of the film profile or the maximum film thickness. A nice agreement could be achieved, confirming the applicability and sensitivity of the developed program. In the second case, a number of different target geometries have been investigated, including edges, angles and slots. From practice, it is well known that due to the distortion and concentration of the electrical field lines between the atomisr and the work piece inhomogeneous film thickness distributions can be obtained that must be also estimated by the simulation program. Again a nice agreement between coating experiment and simulation can be found. These results, obtained with a corona charging atomiser, successfully confirm the applicability of the chosen models for all electrical effects including space charge.