Rockwell Automation 9329 Drive Application Software Tension Control Gen. Units - Manual (Page 9)

FM – Tension Control
Drive Application Software – page 9 of 52
3.0 Overview
There are several methods of controlling the tension of the web (draw, mechanical dancer, load
cell feedback and open loop torque). The Tension Control Module allows the user to configure the
module for the various applications.
3.1 Web Mechanics
All material follows a stress versus strain relationship. When the material is stretched a force
will be generated. The slope of the stress versus strain curve shown below is known as the
modulus and is commonly referred to as Young’s Modulus. As the strain on the material
increases, a point is reached where the material begins to stretch. At some point the strain
will become to great and the material will break. The modules is different for each material.
3.2 Draw Control
Draw Control is the control of difference in line speed between two sections. One roller on
the machine is a master speed reference. The other roll’s speed is adjusted to maintain a
draw to the master section. The speed differential between the two sections is the draw.
Tension Control using Draw is a manual operation. The machine operator adjusts the Draw
set point to maintain the desired tension in the web.
Strain L/Lo
Stress Force/Width
Modulus
V1 V2 V3
100
2
2 1
%
12
x
V
V V
Draw
−
=
100
3
3 2
%
23
x
V
V V
Draw
−
=