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What an impact!



Direct Imaging and Thermal Processing



Published April 7, 2006
Related Searches: Platemaking Flexo printing Flexography Narrow web printing
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Over the past year, we have seen a tremendous increase in the adoption of digital imaging and thermal processing of printing plates for flexography. The major driver for this trend is imaging accuracy and rapid turnaround.

Getting plates to press has been a bottleneck of the flexo production process for years. In the mid-1990s the move away from film began with the advent of the first digital flexo plate imagers. This was a major step change in the imaging process as it allowed digital images to be delivered to the surface of the photopolymer plate with great accuracy and repeatability. Several imaging equipment manufacturers made the move to adapt their film imagesetter technology to address the characteristics of a carbon mask surface on the plate. This fundamentally required higher output lasers than those typically used to expose light sensitive film. The task now was to ablate a mask that had thickness, typically about eight microns or so, and produce an image that had smooth and crisp edges ready for UV exposure. This technology is fundamentally similar among all manufacturers, but the delivery system - how the image is digitally transferred to the plate surface - is handled differently from one to the next.

There is no mistaking the quality improvement realized by the move away from film/plate imaging (the analog process) to direct digital mask ablation. And over the years the naysayers have slowly reduced in number after having taken themselves through painstaking comparative trial after trial to prove it in their own environment.

However, even with the elimination of film in the platemaking process, the turnaround time was not positively impacted, because the imaging time and the increased cost of the digital photopolymer material cannibalized any economic or productivity savings. The fact remained that we still had to process the imaged plate through the same solvent processing systems we had been utilizing since the early '70s. So all of the processing time and the required drying time still stood in the way of delivering plates to the pressroom faster.

The quality improvement of the imaging continued to drive the early adopters to digital imaging and it was advantageous because the printers realized significant print quality improvement overall.

Much of the digital plate volume, however, was still being supplied to the printer by the trade shop or prepress service provider, so the usage was somewhat limited and only relegated to certain high end jobs where it was determined that digital plates were the best choice. This was a hard pill to swallow for many printers, but most especially troublesome for the narrow web flexo market. Why? Because most of the narrow web printing community transitioned to in-house prepress and platemaking as far back as the late 1970s. Many of them advanced even further to implement digital prepress for image manipulation and assembly soon thereafter. So here they find themselves in the next century and having to go back outside to a service provider to have their plates made so they could continue to be competitive with offset and gravure. They had to be selective with their choices as the outside cost of digital plates significantly impacted their profitability in an increasingly competitive label market. After all, digital printing was taking off and driving the quantities ordered to new lows, but the quality produced was outstanding.

Fortunately, innovation has been driving the flexo printing process since its inception in the 1950s, and that drive to compete with litho and roto is still very much alive. The focus now shifted to the platemaking process, the means by which the image would be relieved. So we welcomed the advent of thermal processing at the turn of the century. What was this idea? And would it work in this environment? After many millions of dollars of R&D and the keen eye of the usual early adopters in our industry, the thermal processing concept became a reality. This key breakthrough was the single most definitive advancement to address the issue of fast turnaround in the last 30 years.

In the early years, a single manufacturer drove the concept to become reality. Early adoption happened, as with most new technology, and the innovation gained momentum. Now additional manufacturers are finding their way through the patent issues and introducing versions of thermal processing devices and materials to make the game a bit more competitive.

As with all technology, as adoption increases and the market penetration grows, equipment costs come down and a broader community of prospects find themselves with the ability to afford the price of entry and compete at a higher level. The combination of lower cost imaging devices and the viability of the thermal processing technique has resulted in a new wave of adopters, primarily in the narrow web field. As the costs have decreased, the narrow web printer has discovered that he can produce high quality at competitive prices, turn the plates around quickly and remain competitive in his market as well as push his capability to gain ground versus litho and roto.

Now that the capability is in-house, there is a growing recognition by the printer that the overall process makes perfect sense not just for high end process work but is advantageous across the board. As I have observed, many printers install the digital thermal system alongside their analog solvent systems with the idea that they will run dual systems for a year or so until the digital process proves itself in their application. In recent months, more and more printers indicate that the transition is being made much sooner. The confidence is developed early due to the reliability of the technology and the repeatability of the output versus their conventional systems.

The adoption rate is at the highest now since the late 1990s. OEMs and their distributors are experiencing record sales, a pace which is projected to increase over the next year.

Mounting issues



It is interesting to note that even though digital imaging and thermal processing have raised quality and productivity levels, plate mounting has remained somewhat stagnant in the approaches used by many printers. Through this advanced technology, printers are able to deliver high quality images to a plate that is virtually unchanged from its factory produced state. In other words, now that solvents are eliminated from the process (which resulted in the plate swelling by several thousandths and having to be dried back to or close to its original gauge), the plate is more consistent and requires less impression to print uniformly. As a result, images might not need the trap width of a solvent processed plate to compensate for elongation variability from one image mass to another. (This is a hypothesis being examined by some).

Because of this improved uniformity and color-to-color registration accuracy,  due to the elimination of film and the digital transfer of the image to the plate surface, mounting can be a challenge.

Video plate mounting devices are widely used and have been for years, and significant advantages in registration accuracy have been realized by their use. Moving to a more tightly controlled digital imaging system in prepress merits the use of a more accurate, repeatable mounting system. High magnification video mounting enables the printer to deliver all of the prepress digital accuracy to the press. Once plates are mounted by this method, significant reductions in remounts (most users report virtual elimination of remounts) and reduced makeready times are experienced.

By tightening trap widths in prepress and achieving the superior accuracy delivered by the video mounters, one can truly achieve a competitive equal footing versus many litho and roto applications in the label market.

To utilize a conventional mounting system when working with digital plates leaves you lacking and at the mercy of the operator handling the mounting task. The mounter needs the tools to be able to carry the quality from prepress to the press.

Presses are now equipped with the means by which to hold tighter registration tolerances and monitor that registration accuracy at production speeds throughout the press run. So the system is much more controllable than it ever has been in the past.

These prepress breakthroughs and the use of more accurate tools for mounting and printing will serve our industry well for some time. The transformation of the printer to control the plate output at a higher level of accuracy and repeatability will enhance his position with the customer.
Patrick J. O'Brien is president of Premier Sales Ltd., in Peacedale, RI, USA. In addition to consultation services, Pat calls on nearly 30 years experience in the flexographic printing and converting industry to assist clients with sourcing technology and equipment systems from a worldwide network of manufacturers. He can be reached at 401-783-0817 or via e-mail at pat.o@premiersalesri.com. The web site is www.premiersalesri.com.


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