#56
Author: Tim Walker, TJWalker & Associates
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Subject: Your products require extra precision in your shear knife system.
Your products, 0.0006 to 0.008" thick foils, require extra precision in your shear knife system. All slitting systems exerting a force over a small volume, creating stresses above the material's fracture stress point.The volume of material in the fracture stress zone will crack randomly, forming chips and debris. The material broken and removed is the "kerf". Minimizing "fines" is based on minimizing the kerf volume.This means sharp knives. Shear slitting can be the most precise slitting method because it uses two sharp geometries to create the fracture zone. It can also be the most difficult for the same reason.
I probably need a little more information to help resolve your question.
1. What is the definition of fines? What is the relative dimensions? Have you looked at the fine particles under a microscope.
2. What is the knife system geometry? What is the radius of sharpness on the top and bottom knives? Who provides your knives and knife sharpening? What is the knife material? Which angle are you calling the cant angle? Is this the top blade lean from a from view, or the top blade front edge closing angel seen from a top view?
3. What makes the problem better? worse?
In the end, most slitting challenges are beat by invest in better shear knife systems. This includes the design of the knife assembly, the blade materials and geometry, the sharpening, blade handling, and web handling inand out of the slitting station.
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