Effect of flow rate variation on the frequency response in slot coating process with different upstream sloped die geometries

The sensitivity of slot coating process with different sloped upstream die configurations has been investigated using the viscocapillary model for a coating liquid with constant viscosity (Newtonian) through frequency response technique. Amplitude ratios of coating thickness with respect to a sinusoidal disturbance at flow rate are compared under different input frequency and upstream die lip angle conditions. Amplitude ratio values decrease as the upstream die lip angle increases, implying that the coating system is less sensitive to the given disturbance due to the larger space condition in the upstream die region. Amplitude ratio curves obtained from various conditions can be usefully unified in a single one with the help of new dimensionless time between fluid time scale in upstream region and perturbed time scale by input frequency.