Custom Printing: Folding and Trimming Print Jobs

Photo purchased from … www.depositphotos.com

Think back to making paper airplanes when you were a child. The accuracy of each fold was crucial. Edges needed to line up precisely, or the airplane would plunge into the floor when you launched it. Folds matter.

The same is true in commercial printing. I just received a small brochure for a local bank credit card. It has five printed panels on each side. When open flat, the interior of the brochure comprises all text columns on a white background. Reading from the left, the first three panels take up one column each, and the final two panels on the right extend across the fold as a single, wide panel.

When you wrap fold the brochure, going from the right to the left (this is also called a barrel fold), each panel displays a full-bleed photo of some exotic location you might want to visit. When the brochure is all folded up and you open the front panel to the left and all remaining panels one at a time to the right, you get a “slide show” of locales, each in a different color key, with one or two people who are in some exotic part of the world exactly where you want to be. The fully saturated images on the right (as you again close up the barrel-fold brochure) aesthetically contrast the white background of the informational panels.

All of a piece it is simple, elegant—a masterful promotional design, which has been repeated by any number of other commercial venues.

Folding Creates a Progression of Marketing Images Over Time

The design is great, but it also depends on two things. The first is its operation. This brochure is actually a series of pictures moving through time, much like a slide show. Each visual snapshot presents a new emotional hook. The overall message (apply for the credit card and become a world traveler) moves and grows as you “unwind” the wrap-fold brochure. (Another way to say this is that a brochure is an image “machine” of sorts with its own logical operation or process.)

The other element is the brochure’s technical quality, which depends on the accuracy of the trimming and folding operations, which are referred to by commercial printing suppliers as “post-press finishing work.” Finishing work requires accuracy. Trim edges must be square (parallel or perpendicular to one another, with all sides at 90 degree angles), and folds must be precise enough that type and images fall correctly on their intended panels.

(Consider how you’d feel if you opened a brochure and a column of type fell into the fold on one side. You wouldn’t be thinking about the message of the brochure. You’d be thinking about the flaw in the folding. It would be distracting at the least.)

How Is It Done?

For the most part, custom printing vendors trim stacks of printed press sheets (known as “lifts”) on equipment that first stabilizes the pages, allowing absolutely no movement, and then drives an incredibly sharp guillotine blade through the printed sheets.

If any of the press sheets move, the trimmed corners may no longer be at right angles (90 degrees). This will make precise folding impossible. Paper edges will hang out of alignment. Or pages may be too long or short. Or the knife blade might cut through text, or columns of type may be positioned other than where they were intended to be.

Moreover, if the printed type and photos are anything less than completely dry, the ink may smear or wind up offsetting (marking the printed press sheets before or after them in the stack).

So this is trimming. Folding is slightly different (even though some commercial printing equipment can both fold and trim). First of all, folding equipment works by stabilizing the sides of the trimmed printed press sheets as they shoot through the conveyor at high speed. Metal bars stop the traveling flat brochures and cause them to buckle (fold upward) in an intended and consistent manner. Then rollers complete and flatten the fold as the printed sheets travel further through the equipment in assembly-line fashion. This is the most common (albeit not the only) approach to folding (parallel and perpendicular folds for all weights of paper).

Keep in mind that there are any number of possible folds. In a brochure, some can be wrap folds (as described before, around and around like a barrel), while others may be accordion folds (zig-zag). Some are parallel to one another, while others are performed at right angles. All of this is a result of how the post-press finishing operators have configured the various sections of their equipment.

Moreover, keep in mind that each press sheet usually includes more than one brochure (in this case) on the flat sheet, so the sheets must be cut (automatically) into separate brochures, and the brochures must be folded and accurately trimmed. And all of this is going on at a remarkable speed. (You might want to check out the YouTube videos.)

So any kind of trimming and folding accuracy at all is remarkable.

Things to Consider

If you review the last few paragraphs, you won’t be surprised to learn that folding (in particular) is less precise than custom printing (in which you can often align the various printing plates—maintain “register”—to within a row of halftone dots). Moreover, when you’re folding a printed piece with multiple folds, if you start with a minor alignment error, each successive fold will get worse. Therefore, printers (and books about commercial printing) make it clear that folding tolerances are not perfect. (According to Getting It Printed by Mark Beach and Eric Kenly, folding tolerances range from 1/16” for basic work—for each fold, as opposed to for all folds in a printed piece–to 1/64” for showcase work.)

So how do you avoid disaster? You design around it. For instance:

1. 1. You don’t try to precisely position an important design element. An example might be a 12pt-wide rule line around the front cover of a print book, bleeding off the edges all the way around. (It would actually be a surprising feat for this to be precisely the same width all the way around the book cover due to the less precise nature of folding and trimming.) A design requiring this kind of precision would probably highlight any errors in folding or trimming. (Your eyes are on the lookout for certain kinds of errors, although they are oblivious to others.)

1. 1. Another potentially problematic design situation is a graphic element crossing the gutter. (In my own experience, this is more visually objectionable for photo silhouettes than for straight-edged photos. I think our eyes are more forgiving.) So you can avoid such potential problems by avoiding cross-gutter alignments. Or you can position the graphic on pages that are directly next to one another on the press imposition (you can ask your commercial printing vendor about this). As an example, this would include the absolute center spread of a saddle-stitched print book. As a species we are absolutely blind to (or at least forgiving of) certain visual anomalies and yet seriously offended by others because they just don’t look right.

1. 1. Your printer will be on the lookout for the next two flaws. Specifically, if you have press signatures that are too large in a print book or you’re using thick paper, you may create paper gussets (essentially wrinkles or creases extending–often diagonally–across in the middle of the page). These are ugly. That’s why your printer seeks to avoid them. They can also wind up in a marketing piece that is printed on thick paper and that has too many parallel and perpendicular folds.

1. 1. The other flaw your printer will try to avoid pertains to the grain of the paper. Paper is composed of fibers the majority of which align either along the short dimension (grain short) or the long dimension (grain long) of commercial printing paper. Paper folds more easily, with less paper fiber damage, parallel to the grain direction. That’s why perfect-bound books, for instance, have the paper grain parallel to the spine of the book. This will ensure that the cover lies flat and the pages turn easily. This is also because paper expands and contracts (in response to the moisture content of the surrounding air), with the paper expanding more against the grain than with the grain. This can wreak havoc with the opening, closing, and page turning of a print book if the grain of the paper is not parallel to the spine.

1. On a promotional piece, folding with or against the grain is equally important to your printer. If you’re producing a pocket folder, a fold against the grain will allow the paper to be stronger (since paper tears more easily with the grain). (That is, a fold is smoother with the grain and stronger against the grain.) Your printer will take this into account and may choose to have the grain direction perpendicular to rather than parallel to the spine of the pocket folder (or the pockets, whichever must be stronger). However folding against the grain breaks paper fibers. So a fold against the grain won’t seem as even or precise to the naked eye. This could also affect heavy coverage inks and paper coatings such as aqueous or UV coating, both of which could crack. (Scoring the sheet before folding may resolve this issue, particularly for thicker paper stock.)

The Takeaway

Here are some ways to avoid problems.

1. 1. Learn the potential problem areas of folding and trimming.

1. 1. If you are concerned that these may compromise your design, approach your printer. Ask questions early in the process.

1. 1. Ask for unprinted folding dummies. These will be on the same paper (brand, surface coating, and paper weight) as your final printed product and will show potential folding problems (related to the direction of the paper grain, for example). Paper dummies will also show you exactly how a folded piece will open to reveal the contents of your marketing message. (You can print out your job and glue the panels in place on the folding dummy to see exactly how the final job will feel in the hands of a potential customer.)

1. 1. Keep in mind that for barrel folds or wrap folds each successive panel must be slightly shorter than the prior one. Ask your printer for an exact drawing with measurements for each panel. This will ensure that the position of photos and type will be correct relative to the folds and that the paper will not buckle when folded.

1. Look at other designers’ successful work. Maintain a swipe file of printed pieces you like. Pay attention to the paper the designers have chosen and how the folding techniques support the design and the marketing message. Look for barrel and wrap folds, gatefolds, map folds, and accordion folds. Then pick what you want the printer to duplicate and ask him to note any potential printing or finishing problems that might occur, from cracking ink or paper coatings to potential gusseting.

This entry was posted on Monday, February 21st, 2022 at 9:05 pm and is filed under Folding. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.