Editor’s Note: Given their nature, FLEXO Magazine’s non-commercialism policy was relaxed for all Technical Innovation Award-winning articles. The articles utilize and expand upon information submitted and considered in their receipt of the award.
There is no denying that flexo plate imaging has seen extensive advancements over the past decade. Companies have introduced higher resolutions as commonplace, along with screening technologies that bring more reproducible highlights, shadows and details. Plate companies have developed their own flat top flexo plate technologies. Processing has been able to combine faster and more environmentally friendly systems, while maintaining quality.
However, with the widespread adoption of accurate, consistent and high resolution imaging devices for flexo plates, one major limiting factor for quality has now become the exposure frame. The basic technology has not changed too much. Fluorescent tube exposure frames have been around for many, many years. Unfortunately, inconsistency with light sources, along with the variable timing between back and main exposures, limit the quality of flexo plates.
While technology has certainly advanced, companies we spoke to reported a number of concerns, including:
- They wanted to achieve better and more consistent quality
- They had waste associated with plates that are UV exposed inconsistently (in the plateroom or press makereadies)
- It has become more difficult to find expertise in the plateroom, where consistent plates are required
- Those looking to invest in a new exposure unit wanted to ensure their purchase would be future proof
- Platerooms wanted to reduce touch points
Esko realized the need to expand UV LED benefits to back exposure. Customers indicated that regardless of how consistent main exposure was, back exposure still prevented ultimate consistency. Esko customers wanted a simpler process that didn’t require constant attention and adjustment. Plate makers wanted to make the highest quality and most consistent plate without hiring someone with many years of experience.
Back & Main Exposures
Traditional fluorescent tube exposure was the one plate making step that was not truly digital. There is inherent variation coming from tube age and quality, tube temperature, bed temperature, ballast configuration and many other factors.
Getting consistent light exposure throughout the plate from a frame is difficult to do. Bank lights are not consistent over their lives, degrading in output quality continuously until they reach the end of their 500 to 700 hour lifetime. To compensate, operators have to adjust exposure times quite often. And, when new bulbs are inserted in a light frame, they should be “burned in” for eight hours. Unfortunately, extending the exposure time does not completely compensate for the loss of light intensity. The degradation is also different for each individual lamp, as research has found there is approximately 10 percent variation in output intensity with new bulbs.
The product that came from these needs was developed over many years. Twelve years ago, Esko introduced Inline UV technology to deliver excellent consistency, while maintaining the round top dot geometry considered standard at that time. In 2012, it evolved into Full HD Flexo, with Inline UV2 technology that used UV LED diodes inside the CDI, expanding capabilities to include flat top dots.
This led Esko to develop the XPS Crystal, ultimately part of a completely automated plate making system. It is a digitally controlled UV LED exposure unit, providing both main and back exposures, supporting all photopolymer flexo plates. Plates are placed onto the glass surface, where very accurate back and main exposures—by patented UV LED light technology that, unlike light bulbs, allows very precise control—are conducted simultaneously. Plate consistency is one of the keys to achieving and maintaining optimal print quality. One of the main factors influencing plate stability is the plate’s UV exposure. Unlike UV frames using light bulbs fluctuating in output, the XPS Crystal uses UV LEDs that don’t need warmup time and always emit consistent radiation.
The consistent light source and nearly concurrent back and main exposure deliver unmatched relief and image consistency combined with perfectly formed flat top dots. As a result, these plates deliver the highest level of consistency and quality on press.
Stronger, Consistent Dots & Floor
Using UV LEDs for back exposure delivers precise, consistent relief within each plate and from plate to plate over a long period of time. The operator no longer needs to worry about warming up bulbs before exposure or adjusting exposure times as tubes degrade.
While light frames are inconsistent from one area of the plate to another—and one day to the next—the XPS Crystal utilizes very consistent diode light. It never changes. For example, the optimal relief of a 0.067-in. plate according to Flexographic Image Reproduction Specifications & Tolerances (FIRST) is 0.020-in with a tolerance of ±0.002-in. Light frames typically cannot accomplish this, with ±0.004 tolerance common. This is due to the temperature of the frame, the inconsistent light and other variables.
With the XPS Crystal, customers have reported ±0.001 floor tolerance. Research has proven that consistent relief leads to consistent dots, which leads to consistent print on press. With less plate consistency, it takes more time to get the press on color.
More important, the XPS Crystal exposes a plate, both back and front, at virtually the same time—perhaps a couple of seconds apart. A simultaneous and optimally controlled UV main and back exposure produces highly consistent digital flexo plates—for every digital flexo plate type at every time of the production day. This is simply not possible with a light frame. When using a light frame, a table might be back exposed, then carried to a digital imager, and then main exposed. This could certainly take a few minutes—and perhaps even longer if the operator is required to spend some time on another task.
Esko learned that “dwell effect”—the amount of time between main exposure and back exposure—has a tremendous influence on the formation of small elements on the plate, like highlight dots, tiny line work and text. The longer the main exposure is conducted after the back exposure, the less robustness is in the dots, and the less detail there is.It has been proven the shorter the dwell between exposures, the finer the detail that can be held on the plate. The XPS Crystal does these exposures nearly simultaneously, providing the absolute highest quality dot and fine elements. In addition, those elements are of repeatable quality only when this time difference is fixed.
Making It Simple
The XPS Crystal does all this while being one of the simplest exposure systems available. There is no longer a need for a highly experienced operator. UV LED technology stays stable over time, so there is no more need for constant measurement and adjustment as UV output changes.
The XPS Crystal user interface makes operating the machine very simple. Esko has already done the work for the main exposure for each type of plate—it’s built into the machine. The system comes with preprogrammed main exposure parameters for all the popular plates, an undertaking that took close coordination with each manufacturer. When the machine is installed, the operator just selects the plate.
For back exposure, the XPS Crystal generates a step test with the push of a single button. After measuring floor thicknesses and inputting those values, the software is able to interpolate the exposure setting needed to deliver any relief the operator desires. Instead of changing exposure times, the operator only has to specify the desired relief. That’s it. For any job, he enters the relief depth and the system selects the correct exposure based on the test the operator ran. No longer do users need to “experiment” with the exposure time.
When connected to an Esko CDI Crystal plate imager, the entire imaging and exposure process can be completely automated, reducing operator intervention time by half. The next step is to connect the exposure unit to a plate processor, so the entire flexo plate imaging process is as easy as an offset CTP system.
Companies that have been using the new system have been very pleased with the results.
Glatz Klischee, based in Bregenz, Austria, has been working with the new XPS Crystal 5080 for about six months. The fact the new solution delivers main and back exposure in one step has proven to be a huge improvement in device development.
“Thanks to this technology, we now are able to supply our clients with standard screens (135/160 lpi), up to the absolute premium range with 250 lpi. We can deliver the best possible plate quality with the highest level of consistency, and repeatability that we have not experienced to date,” said Manfred Schrattenthaler, managing director of Glatz Klischee. “In our opinion, UV main and back exposure in one unit represents a milestone in flexographic plate making. It improves plate exposure quality and ensures extremely consistent flexographic plates.”
Inci.Flex, a flexo and gravure prepress business based in Fisciano (Salerno province), Italy, is one of the first companies to install a brand new CDI Crystal 5080 XPS flexo plate production system. The XPS Crystal not only enables Inci.Flex to surpass the quality already provided by Esko Full HD, but is also part of a wider Inci.Flex project, designed to achieve complete automation of the plate production process—thereby reducing human error and speeding up productivity in its plate making operation.
“In addition to the automation and increased capacity achieved with our new Esko CDI Crystal 5080 XPS,” commented Enzo Consalvo, managing director of Inci.Flex, “its ability to produce more stable and reliable dots on the plate ensures our customers achieve excellent printing results across the entire tonal range. This delivers perfect highlights, stable halftones, shading toward zero, smoother transition and more dense, full, uniform solids. Thanks to the high print quality, we are able to offer printers the ability to create high quality flexographic packaging, which stands up to comparison with gravure printing. It has become a true marketing tool for us with our customers.”
The Demand for Quality & Consistency
Just like the Esko CDI 22 years ago, the XPS Crystal is a unique machine. The industry demands the highest quality possible to compete with gravure, offset and digital. CPCs demand higher levels of consistency than ever before. Technologies like expanded gamut (EG) push us to drive more inconsistency out of the process.
This technology has been successful thanks to its ease of use. Light frame bulbs are inconsistent and constantly changing. With the XPS, operators do not have to constantly guess and adjust exposure time. Customers remark that the lack of maintenance, alone, makes the XPS remarkable.
This will drive demand for automated plate making systems that can simultaneously improve quality. Esko saw the same industry enthusiasm when the CDI was first introduced and then, a decade later, HD technology. Initial customer experience is driving the same type of market anticipation. There are thousands of flexo plate imagers—and many compatible flexo plates—that can use this XPS Crystal right now. There are already companies installing the complete, automatic imaging system that includes the CDI Crystal and the XPS Crystal. The next few years promise to deliver even more efficiency and quality, moving even more jobs to flexo.
About the Author: Rory Marsoun, Esko VP, flexo business development, determines the direction of the flexo business in North America, acting as a liaison with the company’s product development staff in Germany. This includes the development of Esko’s new CDI Crystal XPS system. Marsoun has also served as director, software training deployment, Americas, managing the team of experts that installs Esko software and flexo products, and trains new users. As manager – flexo services, Americas, he managed highly skilled specialists who worked directly with Esko customers to implement and optimize prepress and plate making systems. Marsoun earned an MBA and a B.S. in graphic communications from Clemson University. His technical specialties include color, digital imaging, film production, prepress production and proofing.