As the technology for flexographic printing continues to evolve, both quality and efficiency are improving. In order to remain competitive, flexographic printers must stay informed about the latest developments.
Once a sort of “halfway point” between offset and gravure, flexo has come into its own in recent years, in many cases taking volume that might otherwise have gone to one of those print processes, or even digital printing. This is due to its improved quality and ability to profitably produce the shorter runs the market often demands.
Another big change is around environmental sustainability issues, of increasing importance to many brands. Historically, most of the sustainability concerns revolved around the plate making process:
- Was the process using water, solvent or thermal imaging?
- How much solvent and energy were required to make plates?
- What types of toxic chemicals were used?
- What were the costs associated with managing, storing and disposing of them?
Recent customer experience takes the discussion in another direction: With the right plates, many environmental issues are minimized—not in plate making, but in the printing process. At the same time, quality goals can easily be met and press uptime can be significantly improved. This is important for several reasons:
- With a higher uptime standard, a flexo press will deliver more throughput. More jobs and more volume through the press equates to more revenue and profit
- When the press is down because plates need to be changed or cleaned, not only is more time consumed, but also more waste is generated as the press once again comes up to color
- Less print production time translates to less energy usage, improving the environmental footprint of the print job and helping keep costs in line
Water-Washable Plate Benefits
The challenge for plate manufacturers has always been to create a more environmentally friendly plate without losing the benefits and advantages of quality and efficiency. Water-washable plates were developed to meet that challenge and to help printers and converters approach their operations from a much more holistic perspective. In addition to delivering excellent quality, these plates ensure a lower CO2 footprint in print production with a much higher press OEE (Overall Equipment Efficiency). Average improvement in OEE with water-washable plates is 33 percent.
In flexographic printing, highlights can usually cause two potential problems. The first is the highlight breaking point, which prevents a vignette from printing smoothly to zero. Photopolymer flexo plates usually start printing highlights at 5 percent to 8 percent due to dot gain, in the best cases. This means that gradations in vignettes suddenly break at that level, producing a visual contrast with the substrate; a visible breaking point or line well recognized as a print fault in the industry.
This breaking point is virtually eliminated using water-wash technology due to its smaller dot size, low dot gain and high dot stability, especially when used in combination with the latest generation of screening technologies. Extensive plate trials and live production jobs have proven the plate’s ability to print down to 2 percent to 3 percent using classical round dot screening. With the latest screening technologies, the plate is able to reproduce a vignette fade to zero.
Noteworthy benefits listing out as improved press uptime and OEE, reduced waste, profitable production of short runs and faster time to market are making flexography more competitive against offset, gravure and digital print. Industry awards continue to bring the process validity and forge flexo’s recognition as packaging’s preferred print method.
Gateway Packaging: OEE Up 53%
Many now say plate making is the central focus of the bigger picture view of flexography’s environmental sustainability initiatives. Here is one story to illustrate the point.
Based in White House, TN, Gateway Packaging (who ProAmpac acquired in May 2018) is a high-end printer/packaging converter and the largest pet food packaging provider in North America. The company is continually seeking ways to improve products and solve problems for its customers. To meet that goal, Gateway recently completely revamped its flexo plate making process.
“With the variety of flexographic plates and plate making solutions available in the market, we wanted to do a thorough evaluation to ensure our investment decision was the best possible choice,” said Tharrin Akers, prepress manager. “With that in mind, we benchmarked solutions from the leading players, ultimately bringing our selection to two, including Asahi Photoproducts. As a final test, we ran several production jobs using plates to compare efficiency with our current process, and we were very pleased with the results.”
The production test was run on a Bobst 20SIX flexographic press using 40-lb. coated white paper and solvent inks, with a run length of 675,000-ft. In testing the first set of plates, the press ran at 1,400 fpm. The run using competitive plates experienced a total production time of 483 minutes (or just over eight hours) with a total plate cleaning time of 177 minutes and a requirement to clean plates every 2.5 rolls of media at 32 minutes per time.
“When running the water-wash plates,” Tharrin explained, “we were able to run the press at a 17 percent higher speed—1,640 fpm—and only had to stop for plate cleaning once. And that only required cleaning two plates, consuming 20 minutes. The result was a total production time of 432 minutes or 7.2 hours, almost four hours faster and a 53 percent improvement in OEE.”
As a result of these tests, Gateway decided to make a significant investment in a new plate making department, implementing Asahi Photoproducts AWP water-washable plates, a Kongsberg cutting table, a Glunz & Jensen Concept 401 ECLF Exposure Unit and the Asahi Photoproducts AWP 1116 PD Processor. Gateway estimated a payback period of 10 months for the investment, based on the productivity and quality gains it would deliver.
Since installation, the solution has more than lived up to its promise, according to Tharrin. “Our pressmen say these are by far the best plates they have ever run,” he says, “because they don’t ever have to clean plates during the run and setup time is faster since they don’t have to squeeze the plate to get a good impression. We have seen the most improvement on our press, where we can run a very lengthy job and hardly, if ever, have to clean the plates—a big improvement over what we were doing before.”
Tharrin notes that a 30-minute press stop when running at 1,640 fpm has a big negative impact on OEE. He also reports that while first-plate-out time is 90 minutes, the ability to load multiple plates means subsequent examples are produced every 20 minutes. “This results in a faster overall plate production time that has also benefited us,” he explains.
Also important to Gateway, the print quality being achieved with water-washable plates is excellent. “The quality is far superior to anything I have seen with any other type of plate material,” he notes. “With our previous system, we had a lot of problems with dirty print. We didn’t know if it was the plates, the ink supplier or something else. But with these new plates and the same ink supplier, every problem we had was alleviated. We were able to drop these new plates into our current system and we are running better than ever before.”
For Gateway, the focus was on improving the plate making process, which they did, but the real value came on press with improved OEE and reduced waste.
Water Wash vs. Conventional Plates
For a deeper understanding of the difference in performance between water wash and conventional plates, consider the following:
- A drop of ink on the water-wash plate has a higher contact angle than a drop of ink on a conventional solvent-based plate
- When the ink sits on top of a halftone dot, the higher contact angle for the aqueous-based plate pins the ink/plate boundary, and the ink does not move as the plate deforms and the dot is squeezed
- Ink is not pinned with the conventional solvent-based plate due to its lower contact angle. As the ink is squeezed in the plate-to-substrate nip, ink travels down the dot shoulder, resulting in growth of the printed halftone dot
- With water-wash plates, over the course of a long printrun there should be less of a tendency for the ink to build up in the recesses between dots
- The appearance of printed solids is improved with water-wash plates due to the reduced pressure on the surface of the plate, which allows ink to flow together more freely, once it has been transferred from the anilox roll. Also, halftones and solids can be printed on the same plate, which would normally require two different plates, thus saving material. Halftone anilox rollers can be used for printing dense, consistent solids
About the Author: Dieter Niederstadt has 30 years of experience in the printing industry, starting his career in 1986 with an apprenticeship as a phototypesetter in an offset repro house in Dortmund, Germany. He studied print engineering at the University of Wuppertal in Germany and continued his studies at Watford College in the U.K. with a B.S. (hones) degree in graphic media study. In 1999, he completed a Master of Philosophy/Ph.D. in relation to screening technologies applied to flexographic printing at the University of Hertfordshire, also in the U.K.
Dieter worked at BASF Printing systems in Germany from 1999 to 2003, in the applied flexo plate technologies, spending one-and-one-half of those years in South America as a regional technical manager for photopolymer plates. Since 2003, he has worked for Asahi Photoproducts (Europe) and in 2014 was named technical marketing manager. Dieter is a member of FTA and DFTA, a past Forum speaker and participant to various association working groups.