As we’ve noted in past features, for the flexible package printer or converter who works with extensible films and materials, the fight to prevent defect-rendering process deviations is continuous. And this key to reliable defect prevention is the production team’s ability to measure and make machine adjustments that eliminate unwelcome deviations, like web tension transients. Given the opportunity to diagnose a web process problem in detail, technicians from a tension controls supplier are usually able to correct it by installing tension monitoring or control equipment at critical zones on the machine or web press.
A tension zone is any segment of the press in which the tension on the web (in the machine direction) is isolated from other parts of the process. This occurs between driven rollers, between the unwind stand and the first driven roll or nip, and between the last driven roll and the rewind stand. Being that tension control is so important to the package, it’s always worthwhile to occasionally review some of the basics when it comes to the three different zones.