Dynamic Response Analysis and Control of Slot Coating

Abstract

A slot coating application is an attractive coating method for creating a uniform coating thickness over a substrate material. However, a variety of disturbances in operational conditions (e.g., pumping fluctuations, motor system cogging) may lead to unacceptable variations in the final coating thickness. The dynamic response characteristics of the final coating thickness resulting from such disturbances can be computed using a numerical analysis technique that employs a visco-capillary model. In addition, there are two different methods for controlling the thickness of the final coating. One passive control method changes die lip geometry, and the other active control method uses a flow feedback system coupled with a final coating thickness sensor. The passive technique can suppress final thickness variations by 20-30% in a limited number of cases, whereas the active technique substantially reduces thickness variations in every case where the disturbance frequency is less than 10 Hz.