Finding a cure
UV or ultraviolet curing is the drying method used in the printing process and plays a crucial role in keeping production moving along, and minimising errors and wastage.
In the UV curing process, high-intensity UV light instantly cures inks, coatings, and adhesives. Another drying process is curing with infrared (IR) heat. Using infrared heat technology, infrared emitters transmit high amounts of energy in a short period of time, and heat is applied to the desired area for the desired amount of time.
Any products that have been printed, be it books, brochures, labels, or packages, all need to be completely dry before they can be stacked, folded, or moved onto finishing processes. Therefore, UV drying is a way for ink to be cured quickly and efficiently to reduce downtime. As well as these benefits, UV LED curing lamps transmit energy without generating ozone which makes the curing of ink using this process environmentally friendly, too.
Growing in popularity
Benford UV is a UK manufacturer of drying solutions including UV, Eco UV, LED UV, infrared, and hot air. According to Marc Boden, managing director of Benford, LED UV is becoming more popular with technology advancing in the power and efficiency of the LEDs themselves. He also notes that conventional UV is becoming more efficient, especially the company’s MAC 2 system which offers 20% power savings. With the pandemic seeing more and more of us working from home, remote support has also become commonplace, and Benford UV can connect and view customer’s systems from anywhere.
Mark Boden, managing director of Benford UV
“UV or LED UV speeds up production times as the printed material comes out dry so it can be immediately processed,” says Boden, explaining the benefits of curing technology in the printing process. He adds: “It can also be very environmentally friendly when replacing large gas dryers. UV also enables printers to print on almost any substrate, therefore opening new doors to markets.”
With so many options available on the market today, and varying needs from print businesses, Benford UV spends a lot of time discussing what the customer wishes to accomplish by adding UV or IR to the production process. Boden says: “Depending on what they want to do and what they print, we can advise on the correct technology, or in some cases a mix of different technologies. Things such as low migration inks and ink and coating costs need to be considered.”
Higher press speeds
In 2018, Fujifilm launched the Jet Press 750S and one of its most notable features was a completely new drying system. The system was introduced to increase the efficiency of the commercial digital print drying process and facilitate higher press speeds. Andy Kent, divisional manager of Fujifilm Graphic Systems UK, explains how in this system, the printed sheet emerges from the imaging section of the press onto a transport belt heated via rollers, with a vacuum applied as the sheet passes through the drying section.
Drying is then carried out via a combination of the heated belt and hot air which is applied from above. “This new system operates at higher speeds, allowing greater control and fine-tuning of temperatures, extending the range of substrates that can be printed,” Kent explains, adding: “Unlike many other inkjet drying systems, this method does not involve infrared lamps and requires 23% less power, resulting in significant environmental benefits.”
For wide-format print, Fujifilm also relaunched its Acuity range of wide-format printers earlier this year with the Acuity Prime flatbed and the Acuity Ultra R2 superwide-format roll-to-roll press as its two new flagship models. Both presses came with completely new ink curing systems. “In the case of the Acuity Ultra R2, Fujifilm offers customers a choice: LED UV curing for reduced waste and energy use, or conventional UV for high productivity,” Kent explains.
Fujifilm’s Acuity Ultra R2 comes with a choice of LED UV curing for energy saving, or conventional UV for high productivity
“Fujifilm recognises that some wide-format print businesses have to maintain productivity levels that require the much faster speed of conventional UV curing, so is able to offer that choice.” One con of conventional UV curing raised by Kent is that its high temperature can sometimes damage sensitive substrates. To combat this, the Acuity Ultra R2 comes with a chilled vacuum table to maintain substrate temperate while printing and allows the use of thin heat-sensitive substrates, reducing media shrinkage and wrinkling.
For flexographic printing, Fujifilm offers LED UV retrofit curing systems that allow traditional analogue UV and water-based flexo presses to be converted to LED UV curing, boosting productivity and environmental performance while reducing costs and waste.
In the print industry, no technology is developed in isolation but rather always in conjunction with multiple other systems, processes, and consumables”
Kent adds: “In the print industry, no technology is developed in isolation but rather always in conjunction with multiple other systems, processes and consumables. The drying process is no exception. It is an essential consideration in the development of inks, printheads and image optimisation, all of which are core Fujifilm technologies.”
Unique benefits
Since UK distributor, MPL, took on the management of both sales and service for Mitsubishi litho presses back in 2010, the relationship has grown to include responsibility for technical services across the whole of Europe for the now-called RMGT business. Today, MPL also manages spare parts storage and distribution for the former Mitsubishi branded machines across Europe.
(L to R) Mark Stribley and Murray Lock, joint managing directors of MPL
“Our ‘Digital Extra’ promotion focuses on the whole question of how litho and digital complement each other,” explains Mark Stribley, joint managing director of MPL, adding: “Each has its own set of benefits. Litho printing equipment is still able to handle a significantly wider range of stocks than any digital machine. RMGT presses equipped with LED UV are more than capable of printing on plastics as well as lightweight papers and heavier card substrates.
RMGT presses equipped with LED-UV can print on plastics as well as lightweight papers and heavier card substrates
“But more importantly, the cost per copy is significantly less when a run of some 250 to 300 copies are produced on our B3-format press equipped with LED UV when compared to any digital press.”
Reflecting on the history of LED UV technology, Stribley remembers how it was first “pioneered” by Ryobi (now RMGT) and first shown at Drupa in 2008. He says: “Printers are still discovering the benefits on offer from this technology.
“Litho printing that is dry-to-the-touch at the delivery end of the machine adds digital immediacy to the traditional print production. The obvious benefit of this might be faster turnaround of work, but in reality, it also changes the way a factory works and even the space required.
“No longer does work in progress need to lie around the shop floor waiting to be backed up, and, with no set off due to immediate drying, the need for spray powder is eliminated. Jobs are moved into finishing as soon as they are printed, cleaner because there is no spray powder, meaning that they can be cut, folded, delivered, and invoiced more swiftly than ever.”
Longevity and uniformity
Another company that provides a portfolio of LED-based solutions for drying inks, coatings, adhesives, and other UV sensitive materials is Phoseon. The company offers a range of LED UV curing solutions for printers and converters with a variety of sizes for different needs.
Some of the latest developments listed by Phoseon in drying technology include its recently-introduced Nexus ONE air-cooled LED UV curing products for flexographic printing. Nexus ONE LED UV curing lamps deliver maximum power and dose of UV energy for the flexographic markets where high performance is a key requirement.
A spokesperson for the company explains: “The intense UV output of Nexus ONE paired with LED UV flexo inks achieves record press running speeds. Due to the long wavelength range of LED UV, Nexus ONE products have the ability to cure difficult inks with reliably higher quality at faster speeds.
“These air-cooled products efficiently remove excess heat from LED arrays which is critical for the longevity and uniformity of the lamp. Phoseon uses patented air-cooled thermal management techniques that remove excess heat from the system while providing a consistent operating temperature for the diodes to function at maximum performance over their operating lifetime.”
Some benefits of the air-cooled light source is that it eliminates the need for a chiller, removes the risk of condensation, and is easily integrated in converting machines with less infrastructure around the press.
When it comes to making sure you have the best and right drying technology for your business, Phoseon says it’s a very important consideration. “Not all curing systems are built the same, nor do they exhibit the same characteristics. LED UV lamp suppliers have critical choices to make as to the quality, type, material and shape of LED for their systems.
“Key LED characteristics considered by each LED UV lamp supplier will impact the reliability of the product. There are many product options on the market for LED UV but not all of them are built to support rugged and industrial environments. Reliability is very important for UV curing so make sure to find a supplier that does highly accelerated life testing (HALT) to confirm the products are proven to be reliable.”
Environmental considerations
Whilst curing technologies can offer an energy-saving solution to the fast drying of inks, there are some concerns about the use of mercury in drying systems. Boden explains that as a very small amount of mercury is used for making conventional UV lamps, the lamps should be disposed of through a recycling company, as with other types of lighting bulbs.
He adds: “As conventional UV still does not have a replacement technology for all applications, these types of lamps will continue to be manufactured until a suitable alternative is found. LED UV has no mercury in it and is a great replacement for conventional UV, where it can be used. It does have its limitations and so is not useable for everything.”
Also reflecting on the topic, Stribley notes rising costs of energy, the long life expectancy of LED UV diodes, and the high levels of quality achieved in UV curing as consideration to take when looking at drying technology.
He says: “LED UV consumes roughly one-eighth of the power commonly used with currently popular UV products. At today’s pricing that already represents a huge saving from day one of operation, and represents a saving that will be repeated day in, day out.
“For many heavy users of UV curing, such as food packaging producers, this factor alone should be enough to make them consider LED UV as the way forward.”
In terms of the long life expectancy of LED UV diodes, which Stribley estimates at being around 15,000 hours, he says: “They are capable of being instantly switched on and off, meaning that this extended life lasts even longer in real terms, and the power savings kick in yet again. They also produce no ozone, meaning there is no need for an extraction system.
O Factoid: The long life expectancy of LED UV diodes is estimated to be around 15,000 hours O
“LED UV printing offers incredible quality as the image is instantly cured without any dispersion or absorption of ink into the substrate. The dot sharpness is therefore second to none. This lack of “dry-back” means savings in ink consumption, possibly in the region of 10% to 15% - another environmental benefit.”
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