Essential folding Terminology

A signature is a complete sheet containing all the artwork for a cylinder. Examining a disassembled magazine or book often reveals how it was assembled from individual signatures. Depending on cutting and slitting, a folded signature can exit the folder with two or three sides open.

Ribbons are created when a printed web emerges from the last print unit and a slitter divides it into two or more parallel streams. These ribbons proceed into folders where they are folded and recombined.

Angle bars reorient a web or ribbon by turning it at a 90-degree angle. Used singly or in succession, they prepare a web for additional folding, turn it over for reverse direction processing, or superimpose a group of ribbons to achieve desired pagination.

Cylinder Impositions refer to the layout of pages on a publication cylinder, which must exactly match the folder's configuration to ensure every signature has pages in the correct sequence and orientation. Various layouts are possible, dependent on folder type, page size and count, press width, and the final trimmed page size. A one-up imposition has one set of unique pages on the cylinder. A two-up cylinder repeats a page layout twice around its circumference. The term "pages around" indicates the number of pages fitting around the cylinder's circumference, not repeats; a "four around" cylinder may have a "one up," "two up," or "four up" imposition.

Pages can be laid out on the cylinder in columns around format, with the head or foot (top or bottom of the page) leading in the direction of cylinder rotation. The alternate layout is columns across the cylinder, where pages are turned 90 degrees and the open side of the book leads. This may also be termed low or high lead edge, based on whether lower or higher page numbers form the lead edge. "Columns around" produces pages with a grain long orientation; "columns across" yields a grain short orientation.

Former folders fold a moving web or ribbon parallel to the web path, in the grain direction of the paper. The V-shaped folding mechanism creates the fold as the web travels over the former board. Tension and friction are carefully controlled via pinch rollers and low-pressure air to limit paper contact with angle bars and rollers. The folded product may undergo another fold by a subsequent former before entering a cutoff section where it is cut into separate signatures.

Combination folders execute a wide variety of folds in the direction of web travel. The second fold occurs at a right angle, with additional folds possible before the web or ribbon exits to the delivery section.

In publication gravure presses, upper versus lower folders describe two typical sections. The upper folder typically slits the web into ribbons and uses angle bars to superimpose (gather) them. Compensating rollers position the ribbons for correct page-to-page sequential register upon entering the lower folder. Upper folders may have other configurations and features, such as formers and add-a-card units. Formers are generally used for newspaper-type products or to reduce the number of ribbons.

Single-width upper folders gather all ribbons into one stream; double-width upper folders send two separate ribbon streams into the lower folder.

Gravure lower folders are often variable size, capable of producing products with different cutoffs from various printing cylinder diameters, and can accommodate four-, six-, or eight-page layouts around the printing cylinder.

Single-width lower folders receive one stream of ribbons, the same width as the signature to be produced.

Double-width lower folders produce two signatures side by side on the same delivery. If the incoming ribbon is two copies wide, a slitter at the lower folder entrance can divide it.

Jaw folders receive a set (or sets) of cut ribbons onto a cylinder. A tucking blade at the center pushes the ribbons away from the cylinder into mating jaws on an adjacent cylinder. These jaws close, folding the signature, and then transfer it by the folded edge for further processing.

Sustainability remains a key driver, with a focus on optimizing material usage and reducing waste throughout the production process. These evolving trends complement the enduring technical principles of print finishing.

Signatures

. A complete sheet containing all the artwork for a cylinder is called a signature. By examining or taking apart a magazine or book, it is often possible to see how it was assembled from individual signatures. A folded signature, depending upon cutting and slitting, can come from the folder with tow sides open or three sides open.

Upper versus lowers

. In publication gravure presses, there are typically two folder sections. The upper folder typically slits the web into ribbons, then uses angle bars to superimpose (gather) the ribbons. Compensating rollers are used to positon the ribbons so they attain correct page-to-page sequential register when entering the lower folder, Upper folders are available with other configurations and additional features, such as formers and add-a-card units. Formers are generally used when the press produces newspaper-type products, or to reduce the number of ribbons on other products.

Chopper folders

. In chopper folders, combined ribbons are run over formers. The ribbons are cut across the direction of web travel. The folder may separate (or divert) the folded signatures from different positions around the gravure print cylinder, and deliver these signatures separately to the chopper folder. The folder mechanism is a reciprocating blade chopping the center of the signature down between a pair of spring-loaded rollers, thus creating a fold.

Variable cutoff folders

. Folders which have only one cutoff are called fixed folders. Variable cutoff folders can be set to produce any product size within the design limits of the folder.

Slitters

. Slitters are rotary knives which cut a web into ribbons, forming separate streams for folding and delivery. Slitters are precision instruments which must be sharpened and adjusted to very tight tolerances.

Cutting cylinders

. Cutting cylinders are a pair of cylinders containing knives and cutting rubbers, capable of cutting through multiple ribbons of paper. Facing the male knife cylinder is a female cutting cylinder, with slots in the rubber strips corresponding to the male blade positions.