The Importance of Tension Control

Tension Control System Solution

Look around you, many of the products you see and use are manufactured using some sort of tension control system. From the package of cereal in the morning to the label on a water bottle, everywhere you go there are materials that rely on precise tension control in the manufacturing process. Companies around the world know that proper tension control is the “make or break” feature of these manufacturing processes. But why? What is tension control and why is it so important in manufacturing?
Before we delve into tension control, we should first understand what tension is. Tension is the force or tension applied to a material that causes it to stretch in the direction of the applied force. In manufacturing, this usually begins when the raw material is pulled into the process by a downstream process point. We define tension as the torque applied to the center of the roll, divided by the roll radius. Tension = Torque/Radius (T=TQ/R). When tension is too high, improper tension can cause the material to elongate and destroy the shape of the roll, or even damage the roll if the tension exceeds the shear strength of the material. On the other hand, too much tension can also damage your end product. Insufficient tension can cause the take-up reel to stretch or sag, ultimately resulting in a poor quality finished product.

Tension Equation

In order to understand tension control, we need to understand what a “web” is. This term refers to any material that is continuously conveyed from a roll of paper, plastic, film, filament, textile, cable or metal. Tension control is the act of maintaining the desired tension on the web as required by the material. This means that the tension is measured and maintained at the desired set point so that the web runs smoothly throughout the production process. Tension is typically measured using an imperial measurement system in pounds per linear inch (PLI) or metric in Newtons per centimeter (N/cm).
Proper tension control is designed to accurately control the tension on the web, so it should be carefully controlled and kept to a minimum level throughout the process. The rule of thumb is to run the least amount of tension you can get to produce the high quality end product you want. If tension is not applied accurately throughout the process, it can lead to wrinkles, web breaks, and poor process results such as interleaving (shearing), out-of-gauge (printing), inconsistent coating thickness (coating), length variations (laminating), curling of the material during the lamination process, and spooling defects (stretching, starring, etc.), just to name a few.
Manufacturers need to meet the growing demand to produce quality products as efficiently as possible. This leads to the need for better, higher performance and higher quality production lines. Whether the process is converting, slicing, printing, laminating or any other process, each has one thing in common – proper tension control results in high quality, cost-effective production.

Manual Tension Control Chart

There are two main methods of controlling tension, manual or automatic. In the case of manual control, the attention and presence of the operator is always required in order to manage and adjust speed and torque throughout the process. In automated control, the operator only needs to make inputs during the initial setup, as the controller is responsible for maintaining the desired tension throughout the process. This reduces operator interaction and dependency. In automated control products, there are usually two types of systems, open loop and closed loop control.