Designed for Top Quality Printing

Top-Quality Printing

Narrow-web flexo presses incorporate a variety of features that 'set the stage' for superior print quality.

THIS YEAR'S JUDGING for packagePRINTING's Excellence Awards had the judges working overtime. The reason: the overall quality of the entries was just so good, virtually each entry had to be analyzed with a fine-tooth comb.

Nowhere was this more evident than in the flexographic printing categories. It's obvious that the design improvements incorporated into today's flexo presses are being put to good use in the package printing industry. As usual, it is not just one upgrade that does the job, but a series of well-engineered pieces that make up the puzzle. And it all starts with the foundation.

Edgar Minino, sales manager for Gallus, Inc., says there are several factors that relate to superior print quality in narrow-web printing presses. As he points out, however, "It all starts with selecting quality materials and committing to tight tolerances both in the building process as well as in the finished product, i.e. the label. … The concept of the cost-value relationship comes into play—high-quality materials cost more, yet set the stage for an unsurpassed level of performance. Building presses with an emphasis on stringent quality ensures consistent performance under everyday conditions."

Ken Daming, Mark Andy's director of product management, points out a few design upgrades that contribute to the impressive improvements in flexo printing. These include self-teaching electronic registration systems, heavier plate roll shafts, higher quality gears to prevent gear marking, and non-stick coatings on idler rolls to prevent ink picking. "All of these additions allow the operator to achieve better and more consistent print quality with less effort," says Daming.

Servo drives are making a big impact on the ability to hold tight registration. They also eliminate many of the mechanical drive components that cause quality issues such as gear marks.

"One huge advantage of a servo-driven press," says Debbie Hanson, marketing analyst for PCMC In-Line Systems, "is that registration can be achieved very quickly and held in steady states, or upon accel or decel of the press. Transmission errors are minimal. Any print quality problems that were inherent in geared presses, such as gear marking, are eliminated."

She further points out that the high-speed digital communications used in servo drives allows tighter control between machine sections, leading to improved tension control and tighter register. "Servo drives also control position with high accuracy," says Hanson. "Controlling position, not just velocity, gives you better control."

Besides many of these machine upgrades, improvements in the flexo printing components themselves are contributing greatly to better print quality. Maher Hanna, president and CEO of Chromas Technologies, points out that the combined improvements in aniloxes, plate material, and ink are allowing flexo printing to rival offset. "The aniloxes have gone from 600 cells per inch for a normal flexo process print to 1200, giving much finer ink transfer. Plate materials have better hold-down and ink-transfer characteristics." He also credits major improvements in UV ink as one of the cornerstones of flexo printing improvement.

Tighter operational control

While today's narrow-web presses have the built-in capability to achieve superior print quality, it will only happen if converters support the process with tight controls over materials and other operational factors. "Converters can no longer rely just on the press to provide the required quality results they are looking to achieve," says Andy Coletta, president/CEO of Nilpeter. "The right peripherals such as plates, inks, sticky back, anilox rolls, and of course, state-of-the-art prepress facilities play an equally important role in the quest for high-quality reproduction." The final ingredient for success, he says, is a complement of skilled operators.

Minino emphasizes the importance of getting off to the right start in prepress. "Consistent and accurate prepress parameters are a must," he says. "You cannot get high-quality results unless your originals are of the proper quality level required."

There are many other factors that go into operating a flexo process for consistently high quality. According to Daming, one of the advantages that a flexo press has over an offset press is ink laydown consistency. To take advantage of this inherent capability, converters must follow up a consistent process in the prepress area with proper maintenance and ink management.

"The pressroom must maintain their anilox rolls properly—keeping track of exactly which roll ran each job, and cleaning them properly each time," states Daming. As for ink, it must be of a consistent quality and viscosity. "If the operator is required to mix additives into the ink," he says, "it will be very difficult to maintain consistency."

Narrow-web flexo presses

Nilpeter's FB-Line of flexo presses are designed specifically for the label market and offer three web widths: 10˝, 13˝, and 16˝. The presses can run at web speeds up to 750 fpm and can handle repeat lengths from 5 1⁄4 to 24˝.

The Comco ProGlide MSP from Mark Andy has the ability to handle a wide range of substrates from 1-mil unsupported film to 24-pt board stock. It's available in web widths from 10˝ to 26˝, provides repeat lengths up to 32˝, and can run at press speeds up to 500 fpm, standard (750 fpm optional).

PCMC's Webtron X-10 flexo press has incorporated a variety of design changes to improve registration, print quality, and changeover times. The eight-color frame allows a print width of 10˝, repeat lengths from 6˝ to 18˝, and speeds up to 500 fpm. Fast changeovers result from a cantilevered design, a short web path, and on-the-fly lateral adjustment for accurate set up.

The Model 400 15˝ press from Ko-Pack combines flexographic printing technology with in-line letterpress, UV waterless offset, and screen printing, along with rotary diecutting capability. The flexo printing units offer both open chamber (standard) and closed chamber (optional) to allow the use of either water-based or UV flexo inks.

Gallus' RCS 330 is a completely servo-driven press that can handle UV flexo and rotary screen printing, UV varnishing, and diecutting in a single pass. The servo-driven capability allows for very low waste levels as the press can quickly re-establish tension and registration control when starting up after a production interruption.

Taiyo Kikai's Model TLC-450-4F central impression flexo press can process flexible films, shrink films, cartons, and labels at speeds up to 393 fpm. The press can handle web widths from 8˝ to 18˝, with repeat lengths from 12˝ to 24˝.