THE MECHANICS OF TENSION CONTROL （张力控制的机制）.pdf

THE MECHANICS OF TENSION CONTROL By Jeff Damour CONVERTER ACCESSORY COPORATION Wind Gap, PA USA Introduction This presentation is a basic tutorial in the mechanics of web tension control. We will discuss: 1) What is tension? 2) Why is tension important to me? 3) Where is tension control important in the process? 4) How do tension controls work? 5) What is the difference between closed loop and open loop tension controls? What is tension? For the purpose of this presentation, tension is defined as the force applied to a continuous web of material in the machine direction. 1 Typically, tension is measured in PLI (Pounds per Linear Inch) in the US. If you know PLI and you want to know total tension applied to the web, multiply PLI times the width of the material in inches. If you know total pounds of tension applied to the web and you want to know PLI, divide the total pounds of tension across the web by the width of the web in inches. • PLI (Pounds per Linear Inch) = total pounds of tension / web width in inches • Total pounds of tension = PLI X web width in inches The tension applied to a web can be described as the webs tautness as if you hung a weight off the edge of the web. The tension on the web would be equal to the weight in pounds. PLI would be equal to the weight in pounds divided by the web width in inches. 2 Why is tension important to me? • It is impossible to control your web without proper tension being applied to it. The web must be “in traction” with all machine idler rolls and driven rolls to ensure proper web handling and control.