22 September 2015 Analogue Printing Technologies

LED allows litho to fight back against digital

A 520mm press equipped with an LED UV curing system offers a powerful alternative to top of the range digital presses says Ryobi dealer Apex Digital Graphics.

The LED UV revolution in print was unquestionably led by Ryobi. At Drupa 2008, the company revealed a 52cm press on its stand where a blue light glowed between the cylinders.

This was caused by an array of Panasonic LEDs tuned to emit short wave length UV light, only four years after Nichia Corporation scientist Shuji Nakamura demonstrated that this was possible. Ryobi had been working with Panasonic and ink supplier Toyo for two years at that point.

The early LEDs were limited in power output, which restricted the types of work that might be printed. But the potential was clear, underlined by the stream of press and consumables developers heading to the Ryobi stand. Since those days, the power and reliability of the LEDs themselves has increased steeply while their cost has fallen. The initial cost of an LED array is still significant, and higher than equivalent mercury vapour lamp systems, but the life time of an LED is probably more than a press.

LED is a digital system: it is either on or off. There is no fall off in power as can happen with a mercury vapour lamp that is not replaced swiftly enough. The diodes can be set to operate only over the print area of a job. And because the energy produced is all about UV light, no extraneous energy in the form of heat reaches the sheet, allowing plastics and other temperature sensitive materials to be printed. There is heat generated as the LEDs are themselves not 100% efficient but this is easily ducted away from the diodes and the press.

The energy generated is in a narrow spectrum and needs photoinitiators in an ink or varnish to work at this wavelength. These compounds become the cross linked lattice that traps the pigments in the curing process. But they are relatively expensive, hence the cost of the inks.

However, with more powerful LEDs, fewer photo initiators will be needed, and with increasing demand for the inks, the supply of photo initiators should increase. All of which will contribute to a fall in the price of ink, something that is already happening. Because of the narrow wavelength of the UV light, there is no formation of ozone which would need to be ducted away from the working area.

Ryobi's introduction of LED UV related to the Great Eastern Japan earthquake which damaged the country’s capacity to produce electricity and accelerated trends to reduce power consumption in industry. Every Japanese organisation had to do its part and in printing the impetus to cut energy consumption drove demand for UV curing instead of energy hungry combined hot air/IR dryers.

Single-lamp UV systems, like Komori’s H-UV were on hand to meet this demand (it too had been introduced ahead of the legislation which followed the earthquake). LED is more efficient still, which combined with new types of motor drives and smart engineering have slashed the power needed to operate a printing press.

In Japan new generation UV printing has become the standard for sheetfed commercial printing, and is starting to encroach on web offset. Ryobi has more than 200 presses in Japan with the LED system it has pioneered with Panasonic. And the word about the benefits the technology delivers is crossing to the Americas in one direction and to Europe in the other leading to installations on both continents.

While Apex Digital Graphics, Ryobi’s UK agent, was aware of the energy saving benefits of new motors and engineering initiatives, it had not been able to quantify them until a few years ago. At that time a customer compared the power needed by a B2 Ryobi machine against a German competitor as part of its ISO 14001 commitments. It needed to cut energy use and to use more efficient machines when replacing older technology. “We discovered that the power consumption on the Ryobi 750 was a genuine measurable USP,” says Apex managing director Bob Usher.

Now history is repeating itself as LED UV starts to gather pace. The company showed LED UV for the first time in the UK at Print Efficiently in 2014. That was followed by installation of an SRA1 Ryobi 920 LED press at ABC Print Group in Hereford. And there has been a steady stream of demonstrations and inquiries since.

As the result of one of these demonstrations, followed by the installation of a Ryobi 524 with Ryobi LED UV, that has led to the appreciation that this format and style of printing can take on digital printing. This is because the sheet that has been UV cured is as dry as one that has been digitally printed. Digital looses one of its advantages over litho.

With conventional litho the ink used needs to dry through oxidation and evaporation of solvents used. While drying systems on press help with this, it remains an imponderable. Different ink coverage and different papers can affect drying time. It is impossible at times to guarantee a short delivery time, especially on uncoated papers.

UV curing overcomes this because sheets in the delivery are perfectly dry. It is possible to cut, fold, glue and stitch immediately, exactly as a digital press might do. With the advantage that cost per copy on litho drops away quickly, and that the litho press is much faster than the digital, helped by on press automated set up and colour controls.

The new customer had been a digital-only business, which found itself spending £55,000 a month on litho in behalf of its clients. This was comfortably enough to underpin investment in a litho press and the company, like the earlier environmentally led customer, produced its own financial projections. The Ryobi with LED UV won out.

“And,” says Usher, “the litho press is far far more versatile than a digital machine. It can print on a wider range of substrates, 500 micron board is not a problem, and colour control is better managed. There is also the issue that the litho press will retain a resale value which digital will not.”

Apex is gathering a full financial breakdown between the offset press and the digital presses the customer has. “But it seems that 330 sheets is the cut off,” Usher says. “LED is giving litho the chance to fight back.”

He acknowledges that the battle is probably lost with regard to portrait feed litho which has been replaced by digital printing, but with landscape formats, litho now has a strong hand, something that Heidelberg is also recognising as it introduces LED UV.

The technology addresses the weak points in litho: that large amounts of space were needed to store pallets of work in progress while waiting to be finished. When sheets are instantly dry, this is no longer necessary. Moreover the risk of marking is much reduced and finishing equipment does not get clogged by spray powder because there is none.

Then there are more intangible issues. “Commercial printers like to negotiate prices of paper, of plates and ink. With LED they still have the same capacity to negotiate, while with digital printing, they are restricted,” Usher continues.

The initial cost difference between a top end digital press and the Ryobi LED UV is not great, levelling the playing field between the technologies. With automated set up and digital file transfer, the litho press is effectively a quasi-digital machine in any case, making ready in four minutes. On neither press is first sheet saleable, and litho quickly catches up with digital once running.

“We are quite confident that we have the basis to show people LED in operation in a commercial environment and that these are people who are making money from doing trade and commercial print work and they are using LED because it is cheaper than digital,” says Usher.

Apex plans to have these calculations complete by the time Print Efficiently 2015 opens its doors in October.

Apex will also supply the Cron plate system with the press as either a UV imaged plate or a thermal plate. The former has long been a goal in platemaking as the conventional presensitised plate is a robust mature product, and substantially less expensive than a thermal plate. Four UV plates from the Cron will cost less than £4, says Usher.

Early versions of Computer to Conventional Plate suffered from inconsistent imaging results because the marriage of imaging unit and consistency of plate coating was not aligned. The Chinese developer has closed that loop delivering a plate than can be trusted and a platesetter that has trouble-free automation. The resulting plate can stand up to the harsher UV on press conditions and deliver a run length well into six figures, without the press needing to change chemistry.

Apex completes the plate system with an FFEI workflow, equating to a package that is to a very large extent the digital litho set up.

Digital wins in terms of being able to print “every page different” and to print in collated page order for books, manuals and similar products. Ryobi has produced machines that include Kodak Prosper inkjet headsto include variable data on an otherwise static litho page, though not for European printers to date.

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Apex Digital Graphics showed LED UV for the first time in the UK at Print Efficiently in 2014. That was followed by installation of an SRA1 Ryobi 920 LED press at ABC Print Group in Hereford. And there has been a steady stream of demonstrations and inquiries since.

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While Apex Digital Graphics was aware of the energy saving benefits of new motors and engineering initiatives, it had not been able to quantify them until a few years ago.

At that time a customer compared the power needed by a B2 Ryobi machine against a German competitor as part of its ISO 14001 commitments. It needed to cut energy use and to use more efficient machines when replacing older technology.

“We discovered that the power consumption on the Ryobi 750 was a genuine measurable USP,” says Apex managing director Bob Usher.

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