Paper Grain Considerations
Folding Methods | Types of Folds | Off-line Folding Equipment
|There are many digital printing devices that offer online folding as a standard feature or as an option. There could be limitations as to the number of folds that can be performed depending on the type and model of the digital printing device. Some of the more complicated folds may have to be performed with off-line equipment, which of course, creates an additional step in the workflow and a possible increase in the price of the print job.|
Paper Grain Considerations
Regardless of the type of equipment that is used, the grain of the paper plays a major role in determining the type of fold to use for a specific digital print project. The grain also has a major effect on the success of the fold.
Paper stock that is folded parallel with the grain of the paper will fold cleanly. A clean fold is produced because the paper fibers (grain) are running in the same basic direction as the fold, therefore few of the fibers provide resistance to the folding action, which results in a clean, high quality fold.
When a fold is applied perpendicular to the grain of the paper, the resulting fold could have a ragged appearance. A ragged fold is produced because all of the fibers are folded at one time, which creates resistance to the folding action. The ragged appearance of the fold is especially noticeable when folding heavy stocks. Scoring the stock prior to folding is one method to alleviate this problem.
Scoring Prior to Folding
A score is a crease which is applied to the paper stock allowing it to be folded easily. Many types of digitally printed applications are scored prior to folding. A score could be used to crease the cover of a publication, which allows it to stretch around a group of pages that will be bound together, or a score could be used to apply a light crease on the internal pages of the publication to make the folding process easier, especially if the fold is against the grain of the paper.
|Parallel scores are described as scores that run in the same direction that the paper travels through the digital press or the finishing equipment and/or are parallel with the grain of the paper.
||Perpendicular scores run in the opposite direction that the paper travels through the digital press or the finishing equipment and/or are perpendicular to the grain direction of the paper.|
See the article, "Scoring Digital Print Projects" for more information on scoring.
A knife fold is best used with heavy stocks and when the fold must be cross grain. A blunt steel blade pushes the paper between two rollers to create the fold in the desired location on the paper.
To create a buckle fold in a digitally printed application, a document passes through a set of rollers and into a plate where the paper stops at a backstop.
When the paper strikes the backstop, it buckles and is forced downward and into a set of nip rollers.
The nip rollers grab the sheet at the buckle and pull it through, pressing a fold into the sheet as the paper passes through the rollers.
If a digitally printed application requires several folds, additional plates are set up so that the material can be folded in multiple locations during one operation.
The fold or buckle location is adjustable by altering the stop mechanism, allowing for different folds to occur, depending upon the requirements of the digitally printed application.
Types of Folds
Most varieties of folds fall into two categories: parallel folds and right-angle folds. Print products incorporating parallel folds have folds that all run parallel to each other. Print products with right-angle folds have folds that a perpendicular to each other.
Common Parallel Folds
- 4-Page Standard / Single / Half
- 6-Page Standard / C-Fold / Business Letter
- 6-Page Standard / Gate
- 6-Page Accordion / Z-Fold
- 8-Page Parallel Map
- 8-Page Reverse Map
- 8-Page Parallel / Roll
- 8-Page Accordion
- 8-Page Double / Double Parallel
- 10-Page Accordion
- 16-Page Parallel Booklet
Common Right Angle Folds
- 8-Page Booklet with 2 Right Angle Folds (French Fold)
- 8-Page Right Angle - First Fold Short
- 12-Page Letter
- 12-Page Broadside - First Fold Short
- 16-Page Broadside
Off-line Folding Equipment
|Some digital printing presses are able to fold documents with standard or optional online folding devices that have preset standard folds. Some applications may require special folds or perhaps the digital printing equipment may not be capable of performing online folding at all, which means that the folds must be applied the printed piece as a separate operation. Off-line folders for digital on-demand printing applications offer a variety of preprogrammed folds and automatic settings.|