Web Winder Controller
WWC

Next Generation Take-up

The science of optimizing the geometry and the winding tension of web materials as it is wound onto a roll has come along way with the advancement of technology. A typical web take-up consists of a driven roll or spindle onto which the web is wound. This is known as a "center-wind". The motor and gear arrangement that drives the center-wind provides torque which turns the center-wind and produces a tension on the web being wound.

Traditionally, the amount of torque was held constant throughout the build of the package which resulted in a linearly decreasing tension on the fabric as the roll diameter increased. In some instances, depending on the type and texture of the fabric, an improvement in the performance of the winding process was realized by introducing a "taper" or gradual decrease in the center-wind torque which linearly decreased web tension at a greater than normal rate.

Some of today’s fabrics require more sophisticated control of web tension to achieve desired winding performance. Slick textures or finishes can cause one layer to slip over another causing bunching, wrinkling or fiber breakage. In these cases a tension "profile" must be developed and the center-wind torque must be precisely controlled to assure that the web tension is correct at all stages in the roll winding progress.

Precise tension control is achieved by the use of closed-loop feedback, which constantly monitors actual web tension and regulates the center-wind motor torque to force the tension to comply with the programmed profile. Web tension may be monitored using tension-sensing rollers or strategically placed load cells that give an electrical output proportional to force. A special controller then compares the tension value to the programmed value in a "look-up table" and thus commands the motor drive to apply the necessary power to the motor to produce the required torque.

This approach handles the in-progress tension control nicely. However, in some applications the tension values during winding starts and stops is very important as well. The dynamics of the fabric roll may require that during periods when the winding of the fabric is stopped the tension must be ramped down to prevent gradual slippage. Re-starting may require a specific tension ramp-up to correct value.

In some applications the required approach may be to "maintain maximum tension possible just before over-slip". This requires sensing and control based upon web linear displacement and take-up roll angular displacement.

Some web processes, such as weaving, cause the fabric to be delivered to the take-up in an incremented or "jerky" motion. In fact, the web movement may even reverse direction briefly with each increment forward. Steady tension may not be the best. The take-up must take this into account and respond by making the tension "comply" to these motion surges. This can have a significant effect on winding performance.

Today’s fabrics require going beyond the traditional methods to the "next generation" of web take-ups. New technologies allow control of winding performances like never before. And the flexibility to easily adapt to the new fabrics needs of tomorrow is a must.

Selectronics, Inc. designs and manufacture web tension controllers that provide all of these control strategies. Our mission is to apply the optimum sensing and control methods to achieve the best fabric-handling performance in the winding process.

For more information about this product, please contact us.