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Direct lasers get to the point

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Persistent and incremental quality improvement in flexo printing continues through technology developments such as direct press drives, anilox rollers with better cell geometry and better inks.

In this Drupa year, however, none of these has made quite the impact of the simple issue of plate imaging.

The structure of plate dots has been a favourite of Creo , while its arch-rival Agfa (with film-based systems) has focussed on the difference screening such as its cross-modulated Sublima technology can make in a flexo environment.

Both take for granted the advances which have already been made through digital plate imaging, typically using a mask layer, which is exposed prior to further processing.

Apart from Creo and the Esko-Graphics (ex Barco)/Dupont alliance, there’s competition here from others including enthusiastic newcomer Lüscher with its internal drum FlexPose system.

In Creo’s case that’s meant Maxtone-hybrid screening for flexo and the HyperFlex system, working on a combination of its ThermoFlex platesetters and Prinergy Powerpack workflow.

The latter won the company a GATF Intertech award, and helps develop a structure which makes it easier for plates to hold fine dots. Another Creo initiative has been a system to deliver smoother ink coverage, with reduced ink pooling on areas of solid colour, which Creo calls DigiCap.

A compact sleeve option with a cantilever arm designed to make loading and unloading on the CDI imager easier, was among several Esko-Graphics releases for flexo at Düsseldorf. The option is designed for mid-size webs with a maximum sleeve length (or print width) of 1300mm and repeats up to 800mm.

The company, which announced its merger in time for Ipex, now claims 400 CDI sites worldwide and 75 per cent of the market, modestly crediting itself with the increase in quality, reliability and consistency which has prompted a rise in demand for flexo-related packaging.

But for many, the interesting developments still appear from using a laser to cut and shape the flexo plate dots themselves, and not just their surface.

It’s taken the time since the last Drupa in 2000, when a directly-engraved BASF plate was a big crowd-puller, to bring the idea to something close to its potential.

While it used to be true that the polymer plates of flexo CTP could handle higher resolutions and took less time to image, things began to change with that demonstration and have continued to do so since.

Four years have brought higher resolution imaging through the use of overlapping laser spots, as well as the faster imaging seen in all areas of CTP.

Systems now use not one, but up to three beams, able to remove and vaporise material at different depths through the use of varying energy levels which creates a plate dot with a much better flank construction.

Another development has been to combine CO2 lasers (to roughly form the relief and depth) with the more precise ND:YAG laser, where a smaller spot diameter can fine-tune the shaping process when used with some plate materials.

Investment in such developments has been demanding, and the year saw one of the pioneers, UK-based Zed Engraving join up with Swiss vendor Lüscher, which is now continuing with both technologies.

It is encouraging therefore, to see customer sites making use of both for specific applications.

Lüscher has installed a handful of direct systems since the upgraded technology was shown in Düsseldorf, with one of the latest orders to a US prepress house which already has its equipment.

Carey Color in Cleveland, Ohio, will use the laser ablation system mostly for sleeves for flexible packaging, as well as corrugated preprint and labels and sees it as the means to high-end packaging market positioning.

Meanwhile the advances continue, with the latest development a two-laser system with a total power of 800 watts. For its part, the privately-owned Swiss maker has said it will concentrate research marketing on its flexo, dry offset and letterpress prepress systems.

The company had made equipment such as screen imaging systems, step-and-repeat machines, laser scanners and inkjet devices, launching a large flatbed digital printer at Drupa. Whatever the future of Lüscher’s involvement in these markets, its prepress focus, and that of rivals across all of the plate imaging technologies, is likely to be the flexo industry’s gain.

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