Transforming Art into Science

Blade profiles impact the way the web moves past the knives after being slit. Shear slitting uses two blades to shear the material. These blades are often referred to as the upper blade and the lower anvil ring. In shear slitting there is a nip point where one side of the web is supported by the lower anvil ring while the other side is left unsupported and sheared, creating a fracture in the material. Immediately after shearing, the web has to move past the upper blade, which is positioned as an obstacle in its path. The web will move around the upper blade, under it, or in a combination of the two paths. It is the blade profile that determines this path (Figure 2). For example, a steep grind angle such as 35 to 60 degrees will push the material to the side. As the web moves around the blade, the web will rub against the side of the upper blade, creating friction that results in blade wear. Minimizing the blade overlap and using proper geometry will minimize the rub area. As a contrast, a low grind angle, such as 5 to 15 degrees, will push the material down causing the web to move under the blade.