The third post in our Corrugated Converters at the Crossroads blog series will look at how some pressroom equipment and substrates have evolved to help printers keep up with the times.
Many of the corrugated post print presses running today were installed as long as a half century ago. How can box makers, running this equipment, possibly keep up with the graphics quality and turnaround times expected these days?
The answer is, they can’t. At least not without incorporating the latest machine technology in their pressroom. Advancements in the powertrain, sheet transfer systems, substrates, coating chemistries and drying methods have made a huge impact on the speed and efficiency of the printing process and the quality of the output.
Direct Drive Servo Motors
Conventional presses use mechanical gear systems to drive the anilox roll and plate cylinder in the ink delivery process. But as press speeds and the demand for higher quality print grows, these systems can’t hold sufficient registration and adjust for in-run variation. Wearing of the mechanical gears produce backlash in the system and cause deviations in the print registration. For this reason, corrugated OEMs have followed the lead of other flexo press manufacturers by substituting direct drive servo motors for gearing systems. These new direct drive configurations synchronize the transfer rolls with a much higher level of precision, removing the variability in the process, allowing for more repeatable registration and better control over in-run adjustments.
Similarly, new vacuum transfer technology removes the registration variation from the sheet transfer process. The original systems use a knurled pull roll to grip and pull the sheet through the print area of the press and, over time, create the same registration challenges. As the substrate’s abrasiveness wears the knurling on the roll, the sheet slips and the printed image becomes blurred and fuzzy. New vacuum transfer technology eliminates the mechanical pull rolls, instead using suction to smoothly move the substrate through the press. The system holds the sheet firmly in place and allows for a consistent and superior level of print registration accuracy, even at high speeds. (The elimination of these wear parts also makes set-up times faster, prevents jams and takes up much less space in the machine to make room for IR dryers which we will get to later!)
But the advancements in ink delivery and sheet control are meaningless if the substrate can’t sustain the improved graphics and high press speeds. Printing on corrugated board is challenging. Its absorption and surface tension qualities affect print density, drying, trapping and dot gain. Today’s brand owners are demanding not only eye-catching, differentiated products, but also precise graphical representation of their brands and messaging. So, the market has introduced semi-coated and fully-coated papers on finer fluted board that can support these requirements.
Along with the market’s introduction of new substrates comes the challenge of drying. The new coated papers are difficult to dry at high speed, so dryers must be added to optimize press output. IR dryers heat the ink using infrared energy to accelerate evaporation of the liquid bases, leaving only the pigmented ink solids on the substrate. The technology significantly reduces drying time and allows for drying at full speed with coated papers and high-quality inks. As we mentioned earlier, the adoption of vacuum sheet transfer systems has freed up space in the press to install IR dryers between stations. The overall improvement in color brilliance, gloss levels and processing speeds more than justify the investment in this technology.
The final step is to protect the high-quality graphics on a semi- or fully-coated sheet with UV curing capability. When a corrugated box is being used only for shipment and protection, there is little need to apply a UV coating.
But as corrugated packaging is becoming more of a marketing tool, the coating delivers the same benefits as it does in other flexo markets – maximizing gloss, protecting the print, and improving water, scuff and rub-resistance at full speed. The same goes for UV-curable specialty coatings used to apply finishes such as soft touch, glitter and sand to create innovative, unique-looking packages.
Like ink delivery system OEMs, corrugated equipment manufacturers and paper suppliers have responded with innovations to help converters thrive in the current market evolution. From direct drive motor systems to coated substrates, these new products help optimize pressroom efficiency and profits.
In the next post in our Corrugated Converters at the Crossroads blog series, we will continue to look at how digital technology is expanding into the flexo pressroom and playing a key role in the converting industry. Watch for Part 4 – “The Digital Printing Revolution”
Click on the links below to view previous posts in the series:
Part 1: “The Consumer Is King“ – Read about the forces behind the corrugated package printing renaissance
Part 2: “Necessity Is the Mother of Ink Delivery Innovation“ – Read about ink delivery system innovations