Static control and web cleaning systems play a vital role in the production of high-quality, eye-catching flexible packaging. Their advanced capability in removing contamination from webs, preventing production and waste-related issues, is essential in the delivery of high-quality packaging and printed products.
But in order for a company to achieve maximum efficiency, it is vital to first understand how contamination to certain packaging materials occurs and its impact on the converting process. There are two main reasons a web attracts dust: dirt and assorted particles—the boundary layer created by any moving web—and the generation of static charges.
The boundary layer is caused by the ambient air the web drags along when in motion. It draws contamination to the substrate, trapping it either beneath the layer or onto the web’s surface—or holding it within the layer. The slower the web is moving, the thinner the boundary layer; as the speed increases, so does the layer’s thickness. Static charges, meanwhile, can be generated on packaging and printing lines in a number of ways—via fast-moving web rolls that interact with equipment parts causing friction, by the separation of the roll as it unwinds or through induction from surrounding machinery.
Untreated, the presence of static on a web can attract nearby and airborne particles to its surface, which can cause a myriad of problems during and after production. One such example is compromised product appearance and as businesses compete for shelf space for their products, there is even greater importance placed on the production of high-quality labeled and packaged products that can stand out from the crowd. Contaminated labels can impact final presentation, with print work appearing faded or even dirty. In fact, static’s presence on a web can even impinge on the performance of ink, repelling it away from the surface of a label, for example, and greatly compromising its appearance. Many sectors, especially those that work with food and medical equipment, have stringent laws on hygiene and any packaging or product that is found to be unclean will be discarded, increasing wastage and disrupting production. However, it is not just the web itself that can suffer the consequences of contamination—machinery the tainted web passes by or through can pick up dust and dirt, which can lead to clogs, breakdowns and subsequent maintenance callouts. This causes delays to production and incurs a cost to the company, both in maintenance and in lost business. Static can also pose a potentially serious health and safety risk to staff—while the initial shock itself may not cause considerable pain, involuntary reactions can lead to sudden impact to nearby equipment or other workers.
Given the aforementioned problems static electricity and contamination can cause, investing in solutions to counter these issues is vital to production and business profitability.
Static Control Solutions
Active static control provides the most effective means of neutralizing charges. This technology uses ionization, or ionized air, whereby a voltage is fed to an array of emitter pins mounted on an ionizing bar, creating a high-energy “cloud” of positive and negative ions. Any statically charged surface, of either polarity, passing close to the cloud is quickly neutralized. Implementing static control after the unwinding process and just prior to any printing or packaging forming can allow for maximum productivity, and a reduced possibility of wastage and maintenance issues.
More advanced than ever before, static control bars have developed and expanded in their capabilities alongside the increasing demands converters have faced in terms of their production requirements and industry health and safety legislations. Previously, static control systems were designed to deal with the issue of contamination and material damage first and foremost, with little regard for operator safety. Expected to handle speeds of approximately 492 fpm, a common style of ionizing bar was made using brass tubing with dangerously exposed, sharp emitter pins.
The modern plastic packaging films found today across a variety of industries proved to be a turning point in the converting industry and the development of ionizing systems. Advances in recent years eventually led to the arrival of pulsed DC powered systems, which produce higher levels of power and are far more suited to covering larger ionizing ranges, production speeds and materials than previous systems.
Today’s pulsed DC systems come in a variety of formats to suit short-, medium- and long-range applications. Built to last, ionization bars found across many converting lines are now more resilient to build up and even provide feedback on their performance. In fact, static control technology is starting to incorporate automation within its processes. These advanced systems allow operators to see the performance information of the static control devices on a local user-friendly display, such as a mobile phone, tablet, touch screen or monitor, and make instantaneous amends to the operating settings. These devices can be connected to static bar controllers, which alter the level of ionization supplied from the static bar.
While static control can help deter issues surrounding product quality and staff safety, these devices alone will not solve all problems associated with a statically charged web.
Web Cleaners
Today’s high-speed production line systems make production floors a hot bed for statically drawn contaminants. The introduction of effective web cleaning systems alongside static control increases productivity by reducing maintenance downtime and minimizing the waste caused by sub-quality product.
Web cleaning systems come in two forms: contact and non-contact. Contact cleaning systems incorporate vacuum technology or adhesive rollers. Several different designs of contact vacuum system are available—one employs a low-friction component of the cleaning manifold, featuring a component that makes contact with the web, breaking the boundary layer and releasing the contaminants, which are subsequently vacuumed away. Other contact vacuum systems incorporate brushes to free debris before vacuuming.
Systems using adhesive rollers incorporate twin elastomer rollers, such as Meech’s TakClean. This device makes contact with the full width of the web, breaking down the boundary layer and lifting contamination from the web’s surface. Debris is then transferred to a second roller with a high adhesive mass, preventing recontamination. Adhesive-roller systems perform well on small particles (down to as low as 0.5-μm.), but are not designed for more demanding applications where higher levels of contamination are involved, as the adhesive rolls can quickly become tainted and would need frequent replacement.
Non-contact technologies come in the form of “blow-and-vacuum” and boundary layer solutions. Blow-and-vacuum systems, such as Meech’s CyClean, employ air knives on either side of the web to strip the boundary layer and all traces of contamination from the web’s surface. The presence of vacuum airflows ensures turbulent air is captured and subsequently removed. It is an efficient method, and the systems are typically compact, making for simple integration into existing web lines.
Boundary layer systems, a relatively recent development, feature high-speed, non-contact rollers that rotate at a distance between 0.5-mm. and 1-mm. from the surface of the web in the opposite direction. The roller design is optimized to generate its own high-speed boundary layer, the greater energy of which destroys the boundary layer carried by the incoming web. The low-pressure, high-velocity region created by the roller lifts and removes the smallest of particles from the web and carries them to a vacuum extraction chamber.
Conclusion
Determining which types of static control and web cleaning equipment are most appropriate will require an assessment of current packaging machinery and production demands. It is vital any ionization bars and web cleaners are able to fit onto the production line, keep up the speed of production and fit with the budget available. Assessments should be performed that can help determine the levels of static and contamination that are currently being generated on the line—Only then can the appropriate equipment be selected.
The development of packaging materials and the varying applications coming to market mean that packagers must find ways to keep up with demand and also be adaptable to market changes. As discussed, installing static control and web cleaning solutions can increase the productivity of the converting line, and ensure products are processed to a consistently high quality—the most advanced systems are also highly flexible, helping to future-proof businesses.
About the Author
After graduating from the University of Akron with a Bachelor of Science in business administration and industry marketing, Matt began working with Meech as an inside technical sales and marketing coordinator. Since then, he has been involved in virtually every facet of the business and has worked in a variety of roles, including outside technical service, purchasing, production management, quality control, finance and operations.