Insights and Innovations: LED-UV Curing in Offset Printing

LED-UV curing technology for offset printing can offer fast curing times, energy efficiency, and high-quality results. Transitioning to this technology has the potential to generate significant production, environmental, and cost-saving benefits, but, as with any technology, there are some key considerations.

To find out what print service providers (PSPs) should know before making the move into LED-UV curing, we caught up with Gary Doman, international sales manager at GEW Ltd.; Jonathan Fore, director of product management at BW Converting; Errol Moebius, president and CEO of IST America; and Jeffrey Woloshyn, sales director at Eltosch Grafix.

Printing Impressions: What are some key things PSPs should know about LED-UV curing technology for offset printing?

Gary Doman: Importantly, they’ll understand this is an investment that will enhance the production opportunities of their press, particularly in terms of speeding up turnaround times for their customers via instant curing. The press will require some adaptation, such as using ink and dampening rollers suitable to run with LED-UV inks, but this exploratory process will usually take place prior to installation to ensure the system is means-tested for the application and for the material being printed on.

Jonathan Fore: The sheetfed offset industry was an early adopter of both traditional UV and LED-UV curing technology. That trend has never slowed down, but it is now joined by adoption of UV by some parts of the web offset industry.

Web offset presses are able to use LED-UV modules in a 1-yd.-wide mount and eliminate the need for 40-ft.-long massive ovens that burn natural gas or electricity to dry the printed web while it runs at high speed. This gives printers a huge reduction in energy consumption, more available floor space, and often a rebate from their local energy utility.

It is no secret that commercial printing is on the decline. But sheetfed and web offset presses are also workhorse machines for producing high-end packaging, books (once again having increased demand), and other growth areas. Upgrading presses to LED-UV is a strong business decision for maximizing the productivity, and thus profitability, of existing equipment and being able to compete better in a challenging environment.

Errol Moebius: This is still somewhat of a newer technology, in comparison to the well-known “traditional UV” curing or “electronic beam” curing, where LED has made great advancements in the printing markets. Due to the ongoing improvements in the consumables themselves, along with the deeper understanding and need to adjust the power/irradiance output of the LED arrays to match the requirements for cure, adhesion, and surface protection for specific applications, the space continues to evolve. There are, however, still some limitations that need to be better understood as LED develops. Understanding the application regarding compatibility of consumables and substrate selection can be the deciding factor when opting for LED. Adhesion to substrates, use of multiple colors, higher ink coverage along with density of color, special effects, and then, of course, pricing of newer technology can play an important role in the choice. There are some benefits to power savings due to instant on/off formatting and reduced temperature ranges that are beneficial to the environment, equipment, substrates, and safety that make LED a good choice.

Jeffrey Woloshyn: LED-UV curing technology is becoming increasingly popular in offset printing due to its efficiency, environmental benefits, and ability to produce high-quality prints.

• Faster curing time: LED-UV lights cure inks immediately, allowing sheets to be processed and handled right away.
• Energy efficiency: Lower energy consumption with LED-UV system and less heat generation, making it safer for highly-sensitive substrates.
• Longer lamp life: Typical LED-UV lifespans could be from 10,000-20,000 hours versus approximately 1,000 hours for mercury lamps.
• Environmentally friendly: LED-UV systems do not use mercury, do not produce ozone, and have reduced VOCs.
• High-quality print: LED-UV curing results in crisper images and does not utilize powder since the inks are cured.
• Cost considerations: Depending on the configuration of the press, type of work to be printed, and the necessary curing configuration, the costs of an LED-UV system would need to be developed.

LED-UV solutions would typically use less modules to cure products than a mercury UV system.

LED-UV lights cure inks immediately, decreasing material processing time. | Credit: Eltosch Grafix

Printing Impressions: How do LED-UV systems differ from traditional UV systems in terms of energy consumption, space requirements, production time, etc.?

Doman: LED-UV is UV but with a more targeted light wave running usually at 395nm, but this can vary slightly; GEW supplies LED lamps at 365nm, 385nm, and 405nm, where necessary. As the energy is focused to this particular wavelength, the system becomes much more energy efficient. The lampheads are more compact with essentially no moving parts, such as shutters. No ducting is required for cooling and removing ozone. LED-UV lamps are instant on, instant off, meaning there’s no wasted energy since they are only on during printing. This also means there is no burn-in time or cool down required. This by itself improves productivity as the waiting times are removed. For sensitive substrates, LED-UV has a great advantage due to its much lower running temperatures, particularly where plastics are involved in production. LED-UV is also super efficient when printing white ink.

Fore: LED-UV curing systems use solid-state electronics, in this case light-emitting diodes or “dies,” to emit energy within the UV spectrum. Traditional arc UV, however, uses high amounts of electricity to create an arc between two electrodes on both ends of a UV lamp that generates enough heat to vaporize mercury within the lamp and emit UV energy. LEDs require a fraction of the energy of traditional arc UV and have a more efficient output. LED does more with less. Even though both types of systems still need power supplies, controls, and chillers, LED systems end up consuming about 60% less power than traditional UV.

Traditional UV systems create so much heat, they produce ozone gas. This gas is toxic and must be evacuated from the building with powered exhaust systems. The fans consume more power, and the ducting takes up much more space than a compact LED-UV system.

The LED chips themselves typically run about 20,000 hours before needing replacement, many more if run well below full power. Traditional arc UV lampheads need to be changed every 1,500 hours or so. Additionally, LED systems don’t have shutters like traditional UV, which can break easily and need to be replaced. Overall, by not having exhaust systems, lamps, or shutters, LED-UV systems have fewer moving parts to maintain, leading to many more running hours for a press.

Moebius: Traditional UV systems do require additional power to energize bulbs in creating the reaction needed for specific power output and curing range. Although traditional transformers have been replaced by electronic power supplies which typically reduce the amount of power needed for the initial startup and continued operation of the traditional UV process, the power needed for LED is considerably less. The heat generated from traditional UV also needs to be managed and removed from the equipment and process, carried out by either air or water cooling, which contributes to power consumption. As LED generates less heat, energy benefits in consumption can be reduced along with instantaneous on/off options, further reducing energy consumption. Air, water, and power add to the space requirements for functionality.

During maintenance, a single UV curing cassette lamp module needs to be cleaned. Here, two operators are looking at the end of the press UV curing cassette. | Credit: IST America

Woloshyn: LED-UV systems offer significant advantages in energy efficiency, reduced heat emissions, space requirements and production speeds making LED-UV a more sustainable and cost effective choice.
Energy consumption: Depending on the drying system configuration, an LED-UV verses a mercury UV system could use up to 50%-70% less energy.

Heat emission and cooling: Since LED-UV produces less heat, the necessity for complex cooling systems as used by a mercury UV system is not required.

Space requirements: LED-UV systems are more compact and space efficient. Mercury UV systems require more space due to the larger number of control/exhaust/power cabinets and large cooling mechanisms.

Printing Impressions: What are some of the challenges businesses may face when transitioning to LED-UV curing?

Doman: Just coming to terms with investing in an LED-UV system and making sure the press is correctly prepared. Then enjoy all the benefits and the return of that investment.

Fore: If the transition is from traditional arc UV to LED-UV, it is really only a matter of updating the equipment and hitting the “go” button. The press will already have been converted to UV-ready.

If the transition is from conventional solvent inks, the press will need upgrades first. Some (not all) of these upgrades to UV-compatible parts on a sheetfed press include:

• Ink rollers
• Blankets
• UV check valves installed on wash tanks for rollers, impression cylinder, and blankets
• Wash-up tray blades
• UV formula for press washes for rollers and blankets

This is a one-time changeover and can usually be done in a couple days.

Moebius: Being able to combine the correct mix of consumables with the right substrate mix, ensuring the correct application can be achieved. There is also the cost of the LED systems, which are typically more expensive than “traditional UV” (depending on format size). Then, the costs associated with the inks and coatings. As the process of LED is gaining more traction in the various markets, supply and demand is allowing for pricing all around to become more attractive. This goes with the expected lifetime for replacement of bulbs versus the LED diodes.

Woloshyn: Initial investment costs, training and expertise, and supply chain adjustments due to the possible need to work with new supplies for compatible inks and solutions.

Printing Impressions: What advancements are currently being made in LED-UV technology, and how might they influence the future of the industry?

One of the GEW LeoLED UV lampheads inside a Koenig & Bauer Rapida 105-5+C device. | Credit: GEW

Doman: GEW has made great strides in developing more efficient semi-conductors that create a greater UV dose in the 395nm wavelength while consuming even less energy. This will ultimately influence the traditional/conventional UV user to convert sooner.

Fore: LED-UV technology is making key advances in the capability of the LED diodes themselves. Longer lifespans, higher UV output efficiency, and more available UV wavelengths, measured in nanometers (nm), are some of the key improvements the industry is excited about.

Moebius: Developments are continually being made in all areas, with the largest being in consumables: inks and coatings. Along with the need for a wider wavelength output of the LED diodes, there is support for application adhesion, surface cure, and effects on varying substrates. Working together with customers, equipment suppliers, consumable suppliers, and substrate manufacturers are able to offer the best solution while understanding that there may need to be a “hybrid” solution — some LED and some traditional UV. One can complement the other in some cases.

Woloshyn: Continual LED-UV ink and coating developments to reduce costs and to keep the cost of production lower.

Printing Impressions: How will a print service provider know if LED-UV is right for their business?

Doman: I’d suggest they speak with GEW, not only about UV curing, but about process application. We can assist them in whether it is right for them or not. As I always say, it’s not for everyone.

Fore: On the whole, LED-UV is the right solution for most printers. LED-UV cures just about any inks and coatings that traditional arc UV does, but uses less power, takes up less space, and keeps presses running more hours a day.

The Unity LED system uses built-in quartz optics to deliver irradiance (UV power) and dose (UV amount). | Credit: Baldwin Technology Company

Two possible limits to LED-UV are the need for ultra-low migration inks for direct food contact, and specialized coatings for more industrial applications. Traditional arc UV meets the curing needs
of these scenarios, but they are few and far between.

BW Converting’s brand Baldwin Technology has a full line of LED-UV and traditional arc UV systems for curing and infrared systems for in-line drying. Additionally, Baldwin offers a complete portfolio of equipment that enhances the capabilities of press and industrial production lines, including 100% inspection, in-line blanket, cylinder and cliché cleaning, corona surface treatment, color and register control, precision spray and remoistening systems, and many more.

Moebius: By knowing what the applications for today are and what tomorrow could bring; and doing the homework and research while looking to build good relationships of trust and understanding between themselves and their equipment, consumable, and substrate suppliers; and understanding the needs of their end customers and their market needs.

Woloshyn: A print service provider can determine if LED-UV is right for their business by evaluating key factors: print volume and job types; energy and cost savings; turnaround time; environmental considerations; initial investment; and market/customer requirements.