Best Practices: Cutting Through the Static
Press operators have so much to contend with to make sure that all of the visual aspects of a print job are maintained. Keeping registration in-line and ensuring colors are accurate are all key components of producing a quality packaging job. But, without paying attention to an invisible force than can be lurking on presses, an entire run of packaging can be compromised.
Static electricity throughout the packaging process can wreak havoc on a job, causing print defects, attracting dust and debris onto the substrate and it can even shock an operator. Without proper monitoring and reduction of static, package printers can find themselves at risk from both a print quality and safety perspective.
Among the many issues that static electricity can create, Matt Fyffe, VP and GM of Meech, a manufacturer of static control products, says the most alarming problem stems from the print defects that can occur. In particular, he says that with the rise of digital printing, converters are realizing that as ink droplets hit the substrate, without proper static control, that ink droplet will not remain in its desired position.
“If a web has a high static charge to it, it will either attract or repel the ink droplets from a digital printer prematurely” Fyffe says. “That can cause some ink spidering and webbing, which affects the print quality.”
Other print quality issues that can arise include missing dots, poor edge definition, Pantone variance, web drift and more.
Additionally, with any print process used, static electricity on the media will inevitably attract dust and debris to the surface. This can become particularly problematic in narrow-web flexographic printing because of how close the web runs to the floor.
“If a web of material is running through the press and gets within close proximity to the floor it will pull the dust and debris up from the floor and contaminate the web,” he says. “That can affect print quality, but also coating and laminating – whatever the process is that’s being done at that facility.”
Dust and debris on the web not only leads to print defects, but Kevin Coldren, national sales manager for Simco-Ion, explains that once the defect is noticed, it will need to be addressed, which typically means a job being slowed down.
“Contamination leads to defects and increased downtime of press,” he says. “Static charge will hold a contaminate in place, making it more difficult to remove.”
While static issues can occur at any point along the print path, one area that can be particularly problematic is the rewind stage. Fyffe explains that even if a slight charge exists in the web as it enters the winding process, it will gradually increase as more and more layers are wound up, commonly referred to as the battery effect. This results in a highly-charged roll, which can not only shock someone who comes in contact with it and attract dust, but can cause incorrect roll tension. This can result in damage to the roll through telescoping or core crushing.
But, what can be even more problematic for a converter, is that if a charged roll makes its way to a customer, the charge will still be present, and it will increase as it is unwound.
Addressing Static by Print Process
Because of digital printing’s relative infancy in the packaging world, many converters are still adjusting to the static issues inherent with digital and how they can be addressed. Fyffe explains that handling static in digital printing often begins with ensuring the web is clean prior to it reaching the first printhead. He explains that in digital printing, it’s imperative that all dust and debris is removed from the web in advance, but in order to ensure that can be done, all charges must be neutralized.
Fyffe explains that this process often requires two static bars to be fully effective. One bar is placed ahead of the web cleaner to prepare the web for dust removal. Then, because the web cleaning process generates static, a second bar needs to be placed on the other side of the web cleaner to bring the static charge back down.
“Positioning the equipment is the most important thing,” he says. “If you don’t know where to put it or position it incorrectly, it doesn’t matter how much you spend on the ionizer, it’s not going to function properly.”
In flexographic printing, Fyffe explains that a different set of problems can arise. The static in flexo often needs to be addressed just before the first printing station. This is often because the web has gone through corona treatment, which alters the properties of the web to foster better ink adhesion. As a result of the corona treatment process, the web receives an increased charge. Once corona treatment is complete however, that charge needs to be neutralized before it is printed on.
In a sheetfed process, Fyffe says that static can be particularly problematic in the finishing process. If the sheets have a static charge, as they are delivered, they will not stack properly and can create a blockage. To solve this issue, Fyffe explains that ionizing bars or air nozzles can be implemented to remove static at the delivery stage.
While removing static at the right places and at the right time is essential to maintaining a quality print job, it is also important for operators to keep an eye on static levels and best understand how it impacts their specific equipment. Coldren explains that by doing this, operators are put in a safer position and output levels are maintained.
“A monitored static control system, such as Simco-Ion’s IQ power static neutralizing system that can quickly and clearly advise operators of the condition of the ionizer, charge on the substrate and can react to any changing conditions in real-time, is the best way to control static,” he says. “Advising operators of the limitations of older technology and then demonstrating the benefit of a monitored control system has led to increased safety and output for many of our customers.”
Fyffe explains that improvements in static control technology have also been beneficial to converters in monitoring their static control equipment’s functionality and maintaining efficiency.
He says that most converters are used to AC powered static control systems that plug into a power supply and operate based on that. However, Fyffe says that DC systems are gaining in popularity due to their ability to run on just 24 volts and allow operators to adjust their output according to their needs.
The other positive aspect of the new DC systems, Fyffe says is that they feature clean pins technology. This allows the pins to light up when they need to be cleaned. Prior to this technology, operators just had to clean their systems based on estimations and if cleaning was not done at proper intervals, it could cause the system to malfunction.
“If they don’t get cleaned on a regular basis, they just start losing efficiency,” he says. “Keep in mind, this is high voltage equipment. If you don’t keep the dust and dirt off it, it can fail.”