THE COATING PROCESS

The coating of different substrates is an important part of many indus trial manufacturing processes. The fluids used in these processes have very different rheological properties. They are coated to solid surfa ces with high substrate velocities by dipping, spraying, casting or by the use of knives, blades and rollers. The field of flow between two rotating rollers is influenced by the free surfaces of the fluid and t he contact point between the three phases, solid roller, coating fluid , and the surrounding gas. Viscous, inertial, gravitational and capill ary forces control the velocity field between the rollers. Stable flui d coatings that satisfy the increasingly stringent demands on the qual ity of their surface structure have to be created within certain limit s of the forces occurring. In order to predict these limits, the flow fields have to be completely calculated. Therefore all three conservat ion equations and an additional equation for the position of the free surfaces are solved with consideration of the constitutive equations a nd possible wall slip effects of the coating fluids.