Inline Printing Units

Published: October 06, 2025

A Smart Way to Expand Print Capabilities From a Press

By Garrett Taylor, Sales Director, SOMA North America

As packaging becomes more impactful, price competitive and responsive to sustainability trends, there is often a need to add more print units to a job. But how do you do it in one pass, without investing in a completely new press, or inefficiently running a job through a press a second time?

Printing sophisticated packaging presents challenges. One is production efficiency. If a printer has an eight-color press and a job requires eight ink colors along with a varnish or coating, what do you do for the extra layer? An option is an insetter module that can return — front or back and in register — the printed job back into the press for a second time. It allows the printer/converter to add more ink, coatings, varnishes or other barrier layers to the job. They can even flip the web and run the job again to print the other side. That adds versatility, but at a cost: by running the job again just for a varnish, you're using valuable press time. How do you resolve this without investing in a larger press?

Some printers and converters are installing inline printing units. Inline printing units can be an extremely effective option for printers and converters. They are really just mini two-deck presses added to either the front or back of the flexo press. They incorporate the same decks, mechanically, that are used on a traditional flexo, or gravure, printing press. What they do, very easily, is offer two more print units for a job, without sacrificing the time to run that job through the press again.

Inline units are connected by a platform, with many drying options. Planning often depends upon available space. Depending on the facility, a printer can design a longer horizontal — or even vertical — drying tunnel. A vertical tunnel is good for plants with higher ceiling heights, but with a dearth of floor space.

There is also a practical printing advantage. Many printers use inline units for varnishes or coatings for the outside of the package. After they print it all in reverse, they flip the web over and add a matte varnish coating on the outside, without running the job through the press again. It offers the option to print surface or reverse as well, because they can flip the web.

Laying down a thicker coating of varnish, or using a higher volume anilox, requires more drying time. A press might have a standard four- to five-meter drying tunnel, or perhaps six meters if the tunnel is extended. An inline unit can easily accommodate a six-meter tunnel. Another two meters on the side can extend it to eight meters of drying — more than what is typically offered in eight- or 10-color presses.

Though many printers use an in-line unit for just varnishes and other coatings, it also offers ink flexibility. If you have an eight-col-or press with a two-unit IPU, you suddenly have a quick-change 10-color printing capability.

How well do these print? If you have to add a ninth color on an eight- plus two-color setup, print registration on a good inline unit is not a problem; pretty much always within acceptable registration. The limiting factor is the substrate. If it's stretchy film, as with any press, it's going to be a bit tougher. If an advanced mounter is used for plate sleeves, topographical data can be quickly read and prepared for fully automatic settings. There is no manual burden on the press operator to tell the press where to set impression.

An in-line unit can come with different options; for example, flexo or gravure units. A gravure unit is best for cold seals, because the engraved cylinders can lay down thicker layers. And, while many of these seals or varnishes are added after the press, a good example in front of the press would be when a white coat is run on a dark substrate, first.

Printing with in-line units is gaining steam just from the attractiveness of additional print versatility and efficiency. While the challenge of sustainable packaging appears not as intense in the U.S. - workflow efficiency appears to be more important than in Europe - it still offers the converter the ability to print packaging single pass, on paper, with barrier layers or coatings. A downstream station does not contaminate anything upstream.

You can run sustainable-friendly water-based coatings downstream without worrying about contaminating anything on the press.

How efficient can an inline unit be? We know a converter who printed a job at 500 feet a minute, and ran it back through the insetter and press at 250 feet a minute. They had to run the job on the press twice — and slowly. Now they're running it, single pass, at 900 feet per minute, gaining capacity for more jobs.

While it's always exciting to install a new press and many times it's the best business option, sometimes an in-line unit can be a logical interim step, adding capacity and capability with a relatively minimal investment.

About the Author

Garrett Taylor has more than 28 years experience in the printing and packaging industry, specifically with flexographic printing. He plays a significant role developing SOMA's operations in North America, including assistance in the creation and management of the uniquely innovative Flexo Xperience Center, which brings industry partners together to move flexo forward through collaboration, research, experimentation and training.