Substrate Tension and Web Handling in Knife Coating
topic
Knife coating web handling maintains substrate tension at 50 to 500 Newtons per metre across the machine width through driven unwind and rewind tension control systems with web tension measurement by load cell rolls, with lateral substrate alignment by edge guiding sensors and steering rolls preventing fabric drift that would cause knife contact with fabric selvedge and damage both fabric and knife blade, while wrinkle-free substrate entry to the knife zone being maintained by spreader rolls.
Role
Provides the controlled substrate tension and lateral alignment that are prerequisite conditions for consistent knife gap and therefore consistent coating weight across the substrate width, with substrate tension management being particularly critical for extensible knitted and elastic substrates where tension variation changes the substrate width and consequently the coating weight per unit area through the substrate width change under variable tension.