DWH Technical Topic: Abbott App - TSpan

By Clarence Klassen, P. Eng. 

A new Abbott App – Tension in a Span (TSpan) - is now available which models web tension in a span between two traction points. The app shows the predicted steady-state tension which will result from a speed difference between the first and second drive. Furthermore, it will show the transient response and provide a time constant for this tension change.

The time constant is useful for designing the tension controller. The tension regulator is covered in another app – TTS.

Inputs include the span length, gauge, width, line speed, incremental speed, and modulus of elasticity of the web. Outputs are a graph showing the transient response of the web tension when the speed increment is applied to the 2nd drive. The exponential time constant is calculated.

A gain of tension per speed increment is also calculated. This is the tension that results from a draw or ratio change.

A few observations from the model are:

  • A change in span length affects the transient time constant, but not steady-state tension.
  • Heavier gauge results in a higher tension.
  • A wide web has no change in tension in PLI or N/m.
  • A lower line speed results in greater tension. Normally the incremental speed change is percentage-based (draw or ratio) to prevent a tension change.
  • A higher Modulus (E) results in a higher tension.

As always, I welcome your comments on this app.

More info: www.stevenabbott.co.uk/abbottapps/TSpan/index.html