Ultrasonic Vibrations and Coating Irregularities in Film Transfer Coating

Film Transfer Coating is a common technique for the application of low to medium levels of coatings to paper. At higher coating speeds instabilities can arise which are detrimental to product quality. On the Monash Coater a significant increase in the roughness of the wet coating directly after the coating nip has been observed at speeds approaching 800 m/min. Coinciding with this, a considerable increase occurs in the amplitude of vibrations of the nip in the ultrasonic frequency range. The dimensions associated with the surface roughness are similar to the wavelength of capillary surface waves known to be created by ultrasonic vibrations suggesting that these may be the cause of the increase in roughness.