Static control and web cleaning systems play a pivotal role in the printing of labels, flexible packaging and other formats—wherever the delivery of high-quality products is essential. In such environments, minimizing production- and waste-related issues is paramount to ensure added costs are not incurred.
However, contamination looms as a constant threat, reducing quality and potentially damaging webs used for packaging and labeling. This increases waste and disrupts the flow of production.
In order for a printer to achieve maximum efficiency, it is vital to understand how contamination to flexible packaging and label materials occurs, and the impact it has on the converting process itself. 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.
Caused by the ambient air the web drags along when in motion, the boundary layer draws contamination to the surface and traps it 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 can be generated in a number of ways: via fast-moving web rolls that interact with equipment parts causing friction, by the separation of the web 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, leading to a myriad of problems during and after production. One such example is compromised product appearance—a big issue for businesses competing for shelf space for their products as now, more than ever, there is greater importance placed on the production of high-quality labeled and packaged products that can stand out from the crowd. Contaminated labels impact the final appearance of the product; print work may appear faded or even dirty and print performance can also be hindered, as static’s presence on a web may repel ink drops away from the surface, distorting the finished imagery and text.
But it’s not just visual defects that are the problem. Many sectors, especially those that work with food and medical equipment, have stringent laws on hygiene. Any packaging or product that fails to meet these standards will be discarded, increasing wastage and disrupting production.
Converting machinery and its ancillary equipment can also fall foul of contaminants. The tainted web, carrying dust and dirt, can deposit this debris onto other surfaces, leading to clogs, breakdowns and subsequent maintenance call-outs. This causes delays to manufacturing and incurs a cost to the company through added maintenance and lost business. Static shocks can also pose a potentially serious health and safety risk to staff.
Given the many 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. Today’s technology is more advanced than ever; these systems have been devised in response to the demands being placed on companies within the converting industry, which is seeing more varied web materials and higher processing speeds than ever before. The health and safety of operators has also become more important, so technology that can prevent static shocks to operators has become paramount in the workplace.
Active static control 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.
Advances in recent years have led to the arrival of pulsed DC-powered systems which, as well as producing higher levels of power, are far more suited to covering larger ionizing ranges, production speeds and materials than previous systems. Pulsed DC technology comes 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, some static control technology has started 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, touchscreen 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 onto the web’s surface.
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. To maximize results, static control solutions should be paired with a web cleaner.
By removing contamination—an inevitable byproduct of high-speed webs—effective web cleaning systems, working in tandem with static control, can increase productivity by reducing maintenance downtime and minimizing the waste caused by sub-quality product.
There are two basic web cleaning technologies for breaking the boundary layer of a plastic web—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—a highly-polished steel faceplate, for example—to make 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. While this approach is effective when large particles need to be removed from heavily contaminated surfaces, it can be too harsh a cleaning method for use on sensitive materials—Although some systems feature retractable brushes to avoid damaging abrasion.
Systems using adhesive rollers incorporate twin elastomer rollers, which are in contact with the full width of the web, breaking down the boundary layer and lifting contamination from the web’s surface. This is then transferred to a second roller with a high adhesive mass, which removes debris from the first roller, 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.
Non-contact technologies come in the form of “blow-and-vacuum” and boundary layer solutions. Blow-and-vacuum systems 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. Some more advanced, non-contact web cleaning systems even incorporate static control, allowing for a well-rounded solution that can remove static and contaminants.
A relatively recent development, boundary layer systems 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.
The wide range of applications and materials flexo lines are expected to handle, and the constant pace of new product development, means demands on converters will only increase. Converters must be able to meet these demands and do so profitably. 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. In order to select the right choice of system, a variety of factors must be considered, including the source of contamination and understanding how a customer’s needs are likely to develop in the future.
Recent advancements in wireless technology have also opened the door for more automated processes in static control, which are helping to improve the overall flow of production for flexible packagers. Presenting an abundance of information on a singular device, automated static control allows for preemptive maintenance and on-the-fly changes to static control performance. Businesses should analyze their current procedures on the manufacturing floor and determine whether an investment in technology that can give them a full overview of static control performance would be worthwhile to its operators.
Once all these factors have been considered, only then can an informed decision be made on which of the different approaches to static control and web cleaning are most suitable.
About the Author
Matt Fyffe, VP/general manager for Meech International, is responsible for all of Meech’s operations in the US. Having joined Meech in 1994, he has developed a vast knowledge of the plastics, packaging, automotive, medical, converting and electronics industries. Fyffe heads the five principal sector solutions for Meech in the US: Static Control, Web Cleaning, Energy Saving Compressed Air Equipment, JetStream air knife systems and the IonRinse ionized air-rinsing and air-cleaning systems.
After graduating from the University of Akron with a Bachelor of Science in business administration and industry marketing, Fyffe 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.