By Sam Shea

As the great Yogi Berra might have said, folding paper is easy, until it isn't. Because of the differences between ink and toner, folding pieces that have been printed digitally presents a couple of specific challenges. Doug Bober, digital printing coordinator at PIA/GATF, believes that the two toughest challenges in folding digital pieces are cracking at the fold and static build-up.

If you have ever printed a beautiful brochure only to watch in horror as it cracks at the fold, you know how aggravating cracking can be. Toner isn't as flexible as ink, and it sits on the surface of the sheet, which makes digitally printed pieces highly susceptible to cracking at the fold.

One solution is to avoid the problem by designing the piece so that there is little or no coverage on the area to be folded. Of course, this is not always possible, and sometimes you have to fold along a covered area.

If you have to fold on an area with coverage, there are a few steps that should be taken.

• First, it helps to use "certified" paper. Most digital press vendors maintain lists of certified papers for their presses. Vendor certified paper has been tested by the vendor's press and should run and print with expected results. It should also produce acceptable results when folding (this is not a guarantee, of course, and should be used only as a guide).

• Second, whenever possible, you should lay projects out so that folds run parallel to the grain of the paper. Doug Bober mentions a simple demonstration of the importance of folding with the grain: "It's easy to see why paper grain direction is important by taking an ordinary index or business card and folding it in half one way, then the other. The fold against the grain will be lumpy and ragged; the one with the grain will be smooth." Sometimes, of course, you have to fold against the grain. If you have a project that requires right angle folds, the first fold should be with the grain.

• Finally, a third way to combat the cracking problem is by scoring or creasing. Bober recommends scoring for any folds that have to be made against the grain and on any jobs with heavy coverage on 80 lb. cover or greater. For uncoated paper, wet scoring is also an option, as many folding machines can be fit with an attachment that sprays a narrow stream of water along the area to be folded.

Saved by the Folder
There are a number of folders and folder attachments that attempt to fix the cracking problem. The DigiFold folder from Morgana is actually aimed at the digital printing market and is capable of handling jobs run on digital as well as jobs run on litho. The DigiFold is a suction-fed integrated creasing and folding machine that boasts a maximum speed of 1500 sheets per hour (on standard A4 paper). Large diameter rollers coupled with a knife that is speed matched to the type of paper reduces the risk of marking or scratching.

The Tri-Creaser and Tri-Creaser Easy Fit from Tech-ni-fold are creasing attachments that work with most popular folders. The Tri-Creaser uses a soft creasing rib that gently manipulates and stretches the area that is prone to cracking. Crease width and depth settings are built into the Tri-Creaser for every paper weight, regardless of grain direction and solid ink coverage

Slaying the Static Monster
Another hurdle when folding digitally printed pieces is static build-up. A number of problems are associated with static build-up. It can cause the paper to clinging to itself, rollers, machine beds and frames. It can cause the paper to tear, jam or curl. It can also cause sheet-feeding problems.

According to Bober, the potential for static build-up is greatest after the fuser, which in the process of melting the powdered toner to the sheet also removes moisture from the paper. To combat static, there are some steps that you can take.

• First, maintain humidity at 50 percent (Bober says this a must!).

• Second, it helps to have air ionizers inline with the folder's air system, although this can add to the price of the folder.

• Third, a short-term solution is to use a static elimination spray.

• Fourth, if you have the time, it's best to let the job re-acclimate before folding.

Don't Fold Outside the Lines
Accuracy can also be an issue in folding. I'm sure many of you have seen brochures or other pieces in which the fold or folds don't line up correctly with what's printed on the surface.

Sometimes this problem occurs during the folding process. If a folding machine does not hold registration well, folds might not occur at exactly the right place. However, this problem can also occur if a piece is not designed properly.

For example, in a three-panel brochure in which one panel folds in to another, the inside panel needs to be slightly narrower to prevent telescoping. If this is not compensated for in the design process, the finished piece will either telescope or have inaccurate margins and color breaks.

If you have questions about folding options, a great source of information is the Finishing Experts Group Web site (www.expertsinfinishing.com). The Finishing Experts Group, which is focused on educations and standards for the design and print-finishing industries, attempts to facilitate communication about finishing options between printers and designers.

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Sam Shea is CDPE coordinator at PIA/GATF and can be reached at sshea@piagatf.org.

This article is from the Digital Printing Report, a publication of PIA/GATF's Digital Printing Council and is reprinted with permission. For information about PIA/GATF and the Digital Printing Council, please visit www.gain.net.

4/23/08