Roll Deformation During Blade Coating, 1997 Coating Conference Proceedings

The deformation of a web and rubber-covered roll are modeled in conjunction with the fluid dynamics during blade coating. The web and rubber deformations are calculated using a finite element method assuming linear elastic constitutive equations for the paper web and the rubber cover or the roll. Deformations are also calculated with a simple spring model. The web and rubber have different thicknesses and material properties. The fluid flow is modeled using lubrication theory. The simple spring model for the solid deformation is found to be inadequate for deformations over 5 µm. Fine features of the solid deformation are found to be important. As the deformation increases, the single pressure peak develops a shoulder and eventually a double pressure peak. Further deformation causes a subambient pressure after the heel; this situation leads to a case where no solution to both equations can be found. A dimensionless group is identified to determine this critical case. This behavior may represent an industrial situation where there is a lower limit to the coat weight for a given blade-backing roll system or where coat weight control is an issue.