Proper Tension Prevents Flex-Pak Print Problems
Quantifying the effects of press adjustments requires tension measurement.

The machinery used to create visually flawless printed packaging is hardly ever flawless itself. For the flexible package printer/ converter who works with extensible films and materials, the fight to prevent defect-rendering process deviations is a continuous one.

The key to reliable defect prevention is the converter's ability to measure and make machine adjustments to eliminate unwelcome deviations, including tension transients. Given the opportunity to diagnose a web process problem in detail we are usually able to correct it simply by installing tension monitoring or control equipment at critical zones on the machine or web press.

While many film printers and converters are busy trying to overcome issues of excess tension, some, like a large gravure printer DFE assisted recently, suffer from slack web conditions.

Uncontrolled loose web on the printer's two multizone multi-color presses, was causing the web to 'dip a color' periodically, according to the plant Maintenance Manager, a potential hazard that causes unplanned downtime and lost productivity.

As with instances of excessive web tension, the problems could have been avoided if the press operators were able to adequately monitor and adjust for out-of-spec tension conditions on press runs.

Because of the advanced register controls built into the presses, adding automatic tension controls was not advisable due to potential control conflicts. That left the option of installing a tension monitoring system with alarms that would signal the press operators when a low tension condition was occurring.

The printer started by retrofitting their 36-inch wide web press, a Cerutti 190 8-color press with lamination zones, with ten Tension Roll Transducers and FireGuard tension amplifiers.

Tension was measured by the transducers, then amplified and displayed at analog meters set up in a single enclosure at the operators' main control panel.

The printer went on to retrofit a second press (11- color gravure) with the transducers and indicators. Finally, DFE supplied a special TLS (tension limit switch) option that will trigger alarms at four of the sensor locations when low tension set points are tripped during print runs.

By continuously monitoring their actual running tension at various critical points in the presses, the operators can make adjustments before a print job is negatively impacted and identify press problem areas.

A range of tension measurement and control components and systems are available to fit almost all press geometries and space requirements.