IDE Online Magazine Abril 2017 - Page 89

now available you have a potent cocktail for potential production problems. Today’s lines are capable of running at upwards of 1200 feet/min, packaging is getting more complex, and lightweight substrates such as PET, PVC and Mylar are especially vulnerable to the effects of this phenomenon.

Static arises when an external force causes an electrical charge to move from one material to another, leaving one positively charged and the other negatively charged. Speed and force of the friction, pressure and separation are all factors that contribute to the size of the charge, with increased force or faster processes leading to larger charges being generated. If one of the materials is conductive, it won’t hold the charge, but if the material is non-conductive the charge is unable to move across the surface, creating a static “pool” of electrical charges.

Uncontrolled static can cause products to misbehave – print can be out of register, tiny holes appear in extruded film, and static charges can cause blockages in the most modern machinery – but dust attraction is arguably the biggest issue in a sector concerned with quality control, as airborne particles are attracted to charged surfaces, leading to high reject rates and rework levels where the packaging calls for completely clean substrates.

In order to deal with such varying degrees of dust, a non-contact web-cleaner proves to be an ideal solution, as the system performance is not affected by the contamination level and no consumables are required, which helps reduce ongoing costs. Some of the latest non-contact web cleaning systems designed for the narrow web industry are capable of removing contamination to below 1 micron, as well as incorporating fluid dynamic principles to deliver higher levels of cleanliness for label printing applications.

However, while the web-cleaner provides a solution for contamination on the substrate, there is also the necessity to eliminate the presence of static on the web, which may re-attract dust to its surface. Active static control utilises ionisation technology, employing high voltage AC or “Pulsed” DC to produce ionised air to neutralise surface charges. The voltage is fed to an array of titanium emitter pins mounted on an ionising bar, creating a high-energy “ion cloud” of positive and negative ions. In its AC guise, as the AC cycle changes, positive or negative ions are produced in approximately equal quantities, and a statically-charged surface of either polarity passing close to the cloud is quickly neutralised.

Recently launched static control bars have marked a transition from AC systems to 24v integrated power supplies, providing more efficient ionisation. Long range ionising systems achieve great static control in general applications, whereas for short to medium range applications (with target distances varying between 2 to 20 inches), plug and play bars are better suited. Newer products tend to be more resilient to the build-up of contamination which occurs during their use and also allow for easier cleaning, while their improved shockless design makes them safer for operators to handle.

Being fully aware of the ever-growing importance of the labelling market, and with a long heritage in static and web-cleaning, Meech’s aim is to provide solutions that can benefit companies in this sector and advise them on some of the issues static and contamination can pose left untreated.