Shopping for Corrugated Printing Solutions

Corrugated is a material of significant strength and versatility. The flutes or ribs that form the core of the corrugated sandwich take the shape of an arch. Anyone who has seen a Roman aqueduct or a Volkswagen beetle commercial knows that the arch is one of the most structurally sound shapes in the world. An additional benefit comes from the barrier being somewhat compressible, which gives added protection to the package's contents.

Ironically, corrugated board's very strength is what makes it a fragile material to work with. Think of corrugated's flutes or ribs as a series of waves, with amplitude (height) and frequency (number of ribs per inch) as the defining features. The amplitude and the frequency determine the strength and grade of the material, which translates to its burst strength.

Preserving that inherent structure presents a problem for printers because their process involves applying pressure to the substrate to achieve imaging. Printing direct on corrugated is all about the squeeze and controlling the crush to preserve the material's burst strength. Realistically, you want to achieve a range of between .002 and .003-in. of crush to properly apply the ink that will create the printed image at each printing unit.

Squeeze too much – you'll literally crush out the advantage of using corrugated in the first place. Apply too little pressure, and you're not transferring ink adequately. That's why it's important to carefully choose your press. You want one with printing units that will deliver the precision the job requires and the consistency you need.

Undercutting Your Press

In selecting your press, you first want to make sure it handles heavier board, ideally up to 65 pt. If you want to print thicker than that, you may have to undercut the cylinders of your press. That requires literally shaving them down so they can compensate for the thicker substrates.

As you might imagine, the process is not inexpensive. It can be applied to both new and existing machines, but it limits the press' ability to print thinner stock at the low end of the substrate range.

So if you undercut by 10 pt. you'll be able to print on a corrugated board that's .010-in. thicker but your new minimum substrate thickness is 10 pt. That's why converters should carefully examine their markets, applications and prospects before going the undercut route.

Blanket Coverage

An alternative to undercutting has been developed by offset blanket manufacturers. By working with blankets that are designed to have a greater compressibility than conventional blankets, you can print directly on much thicker materials without as much risk of unacceptable crush to the substrate. Your press manufacturer can help you navigate these waters.

Stock Options

Another major problem encountered by offset printers who are new to corrugated is the inability to match the stock to the job at hand. Flute rating does not translate to the thickness of the corrugated. Top sheets and linerboards of different thicknesses are glued to different flute profiles to provide a range of caliper readings for the same letter flute.


Paper path pointers
Make sure the top sheet is as flat and free of hills, valleys and other anomalies as possible. Remember, you're trying to print with a minimal amount of pressure to minimize crush so you want to make sure the surface of the top sheet is as flat as possible. A thicker top sheet also promotes better printing, reducing the chance for the so-called "washboard" effect in the printed image.

Printing Solutions

Usually offset litho is reserved for higher quality corrugated printing. The advantage to printing direct is that it's a one step process, producing a product ready to be diecut. The other methods require additional steps and expensive equipment or outsourcing if the equipment is not on-site.

Often the high volume, high quality solution is litho laminate. The press can print graphics of the highest quality, typically on something like 100 lb. label stock. The resulting sheets are laminated onto the top sheet of corrugated board and the packaging is created from the composite. The advantages are obvious: the printing can be of the highest quality for maximum shelf appeal, and virtually any grade or thickness of corrugated can be employed, which means structural integrity will not be a problem.

Litho lam production is another reason to use softer compressible blankets rather than undercutting your press. Reason: they preserve both ends of your stock thickness capabilities. That means you can print direct to corrugated or produce litho lam labels on one press.

By choosing a press that has a wide substrate range and employing special compressible blankets, you can truly become a versatile solution- based provider.