Best Practices: The Importance of Ink Systems
It’s easy to take for granted that in any type of printing, ink will meet the substrate as it passes through the press and a printed product will come out on the other side. But, what often gets overlooked is the path the ink takes on its journey to and through the press and eventually, onto its intended surface.
Ink systems, whether pumps, dispensers, tanks or formulations, are crucial elements that play a major role in print quality, efficiency, color accuracy and plant and product safety. Understanding how ink systems can best interface with a printing operation and improving ink management can lead to significant improvements throughout the printing process.
According to Maarten Hummelen, marketing director for GSE Dispensing, the most important element of an ink dispenser is the software that drives it. GSE, which is based in the Netherlands with U.S. operations in Charlotte, N.C., offers a full array of ink dispensing equipment, but Hummelen explains the software capabilities behind these dispensers can help package printers better run their operations.
He relates how GSE has identified specific pain points or “themes” that can be addressed with certain types of ink dispensers and their corresponding software’s capabilities.
The first theme that Hummelen describes revolves around converters that mix their own inks. For these environments, he explains it’s imperative for printers to choose an ink system that best corresponds to the applications they specialize in. For example, he explains that printers using solvent-based ink should ensure their ink dispenser is explosion-proof. Because these solvents are entering the atmosphere around the ink system, if there is a spark ignited in the vicinity, the equipment is liable to explode.
“With solvent-based printers, there’s an explosion hazard because there are solvents in the air and if there’s a spark, then it explodes,” Hummelen says. “So, you better take care that your machine doesn’t create static electricity to create a spark because then your factory can burn down.”
Hummelen says it’s also important to keep in mind that when working with UV inks, UV light cannot enter the system. He states that black hoses and pumps are required, otherwise, if UV light gets in, the ink can cure prematurely.
Another important theme, according to Hummelen, is the dispensing environment. For example, it makes sense for label printers to dispense into smaller buckets because, for the most part, labels require less ink on press. Flexible packaging and paper and board-based applications however, may require more ink and can utilize dispenses up to 50 lbs.
Where software comes into play, Hummelen says, is in managing ink usage and tracking it as it is returned and potentially recycled. He details how in most print jobs, the entire quantity of ink dispensed is rarely completely used. A certain percentage is almost always left over and can be stored for reuse. The software then recognizes the color being stored and indicates the jobs it can be used for in the future, and even if it can be adjusted to create a new color.
“Printers want to buy as little ink as possible,” Hummelen says. “They want to reduce the ink consumption that they have without losing the impact they create with the ink on the package. I think ink suppliers should help the customers to be more efficient and that can be done with these kinds of systems and software.”
Additionally, Hummelen explains that from a safety perspective, software can help with traceability. Utilizing software, he states, can keep track of the ink batch codes that were used on a product, and which codes were combined via recycled ink. This way, he says, converters can ensure they are using qualified ink formulations for each application.
Proper Ink Pumping
When assessing the proper ink pump for a printing environment, Craig Shields, president and COO of Graymills, a Chicago-based manufacturer of inking systems, states the two key areas to focus on are what type of ink will be pumped and how often the ink or fluid will be changed.
Shields explains that different inks have varying viscosities and require different types of pumps. For example, heavier viscosity inks such as UV, EB and some heavier water-based inks should be pumped with either peristaltic or diaphragm pumps, as they are designed for that purpose. Meanwhile, light viscosity inks, such as solvent-based and light water-based inks, could use centrifugal pumps.
The frequency with which inks are being changed becomes an important factor, Shields says, because certain pump systems are easier to clean and change over. For example, he states peristaltic pumps are much easier to clean and better suited for shorter runs, as opposed to centrifugal or diaphragm pumps, which require a full washout to clean.
“The cleanability of the pump is a major factor to consider,” Shields says. “If you’re doing long runs, it’s not as big of an issue, but if you’re doing 20-minute runs, it’s a huge issue. A five-minute clean job on a 10-hour run is a lot different than a five-minute clean job on a 20-minute run.”
These factors, Shields explains, lead to certain segments of the packaging industry relying on different types of pumps. He details that the tag and label segment primarily uses peristaltic pumps, because their easy-to-clean nature makes them better suited for the short run printing common in narrow-web. Meanwhile, wide-web gravure printers often utilize centrifugal pumps, primarily because they have the lowest operating cost, making them a logical choice for long run environments.
Shields also explains that double diaphragm pumps are often used in mid- to wide-web presses, largely because they’re compact, relatively inexpensive and the wash up processes on many wide-web presses were designed for diaphragm pumps. One potential pitfall of diaphragm pumps, Shields says, is they create a lot of high-pressure pulsation leading to “blade clutter,” in which the doctor blade bends with the pulsation of the pump, leading to inconsistent wiping against the anilox roll.
“People tend to compensate by overpressuring their chambers,” he says. “They really crank the pressure on their chambers down, so that means you’re not getting a nice gliding action of the blade on the anilox. You’re actually grinding into the anilox.”
Regardless of ink type or printing process, Shields explains there are rules of thumb surrounding certain aspects of an ink system. For ink tanks, he explains the run length and how much ink is being put down should determine the size of the tank. For example, if a job calls for an opaque white background, Shields states that converters can expect heavy ink usage, and therefore a larger tank should be used.
However, if a job requires a small patch of a spot color, the required tank won’t be quite as large. Additionally, he explains that a pump should not be run above 75% of its capacity, as running it at its limit will increase wear.
Maintaining a Greener Ink
As awareness surrounding food-packaging increases, printers and suppliers need to ensure the consumables they’re implementing are suited for these applications and meet their end customers’ requirements. Todd Dragoo, technical services director, offset/digital, INX International Ink Co., explains that using an ink designed for a commercial application in a packaging application can become problematic due to odor.
Dragoo states that INX International has developed a system designed to function in a “dual use environment,” suitable for both commercial and packaging applications, while meeting Nestlé and Swiss ordinance compliance.
“I’m trying to encourage printers to look at these greener ink options to remove potential odor or other material concerns for those that print in a wide range of applications, even if they don’t require it most of the time,” Dragoo says.
In an operation that is solely packaging-based, Dragoo explains this is a less pressing issue as most of the printed products will be similar and have similar ink requirements, necessitating the greener ink option from the start.