When should a web run higher or lower than the default recommended tension?

The recommended target tension is a starting point, but many factors may mean higher or lower tension is better.

The recommended tension of 10% of web damage is a starting point. Many factors may mean a higher or lower tension is better based on product or process factors, including:

Product mechanical behavior changes with temperature, moisture, or transformation (e.g., hot polymer films will yield at lower stress, so tension is usually reduced when the web is hot, a coated layer may become stiffer after drying or curing).

Tension may be increased:

  • To pull out web bagginess, running straighter and avoiding wrinkles at nipped rollers.
  • To create more roller traction to avoid scratching
  • To make idler roller drag and inertial losses a smaller percent of average tension.
  • To eliminate wrinkles by tension-induced stiffness.
  • To improve concave rollers spreading.
  • To reduce sag in horizontal web spans.

Tension may be decreased:

  • To reduce roller deflection.
  • To reduce web pressure against wrapped rollers.
  • To avoid contact with air nozzles and or air turns.
  • To eliminate wrinkles through reduced roller traction.

Tension may be increased or decreased to reduce the tension differential at a driven roller to maintain tension control.

Tension may be increased, decreased, or tapered to optimize winding and roll structure.