Knife Over Roll Coaters
Knife over roll coaters utilize a precision ground knife blade loaded against precision gap adjustment assemblies to form a gap between the coating knife and backing roll which is typically a precision steel roll. One area where knife over roll coaters are extremely useful is in processes where total product thickness uniformity is of great importance. The reason for this is regardless of the substrate uniformity, the precision gap between the coating knife and the backing roll will result in a total product thickness which is extremely uniform. This is in contrast to pre-metered coating applicators which will provide a uniform coating thickness, but depending on the base substrate may result in a finished product with thickness irregularities. Coating is generally fed into a coating hopper or backup board complete with adjustable edge dams to set the coating width. The feed head and or a coating distribution method within the coating in the hopper are important depending on the coating to help prevent coating defects and thickness variations. Knife over roll coaters are ideal for high viscosity coatings as well as applications with high coat weights.