A rewinding application involves the windup of either web or strand product onto a roll or a coil. The roll is typically driven with a variable speed or variable torque motor drive. If not properly controlled, variation in tension can cause issues including breakage, blocking, and crushed roll cores.
A load-cell based tension control system provides the most precise tension control for the rewinding applications. To control tension, load cells are used on an idler roll or pulley to measure the actual tension for input into a Tension Controller. The controller then supplies an analog output to the drive system to either increase or decrease the motor speed. If a increase in tension is needed the motor torque is increased, and vice versa if a decrease is required.
In many applications, the tension will need to decrease, or Taper, as the roll diameter increases. The reason for this adjustment has to do with the increase in torque on the roll core that tapes place during the increase in diameter (torque = torque x diameter). To avoid crushing of the roll core, a taper can be utilized to decrease tension and, thus, torque.
If the rewinding system experiences any level of mechanical noise or vibration, the controller will also need to differentiate the tension signal from vibration noise. Hardy Instruments utilizes its WAVERSAVER ® technology to ignore the effects of vibration while providing a high level of accuracy in the tension signal.
The Hardy Tension Controller incorporates WAVERSAVER ®, Rewinding control, along with automatic taper adjustment.