A folding machine is a machine

Machine

A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 used for fold

Paper folding

Paper craft is the collection of art forms employing paper or card as the primary artistic medium for the creation of three-dimensional objects. It is the most widely used material in arts and crafts. It lends itself to a wide range of techniques, it can for instance be folded, cut, glued,...

ing, usually of paper.

A fold (in paper) can be made by a Buckle or a Knife.
There are generally three types of folding machines. Buckle Folders, Knife Folders or a Combination of these two types.

Buckle Folders

Buckle Folders work by feeding the paper at high speeds until it hits a stop. The reaction of the paper is to buckle. High friction rollers will then grip the paper and pull it through, that is, the paper is folded by being squeezed between two high friction rollers. The grip of the rollers is caused by the help of rubber or PU. The front edge of the paper went into a so called "pocket". The rollers press on each other by help of a spring. The distance between the rollers can be set.

Knife Folding

The Knife Folding system works by striking the paper with a knife between two rollers. This knife is not actually sharp enough to cut through the paper, it simply strikes the paper along the line through which the fold is desired. Many modern folders however, have a combination of both knife and buckle folding mechanisms. Buckle Folding is the more popular of the two methods, however, Knife Folding is sometimes preferable, for example, when the paper is thick, used as cross-fold or in cases when the paper has been stitched direct in the folding process (Faden Siegeln). Stitched sheets can ruin high friction rollers by parts of the melted thread. Some of the most popular folders used by printing companies and binders are, M.B.O. (Machine Builder of Oppenweiler), Stahlfolder (now by Heidelberg), GUK, Horizon and Baumfolder.

There are 2 types of feeding systems used by folders. The first is flat pile, this is where the paper is placed on a feeding table and each sheet is then transported into the machine by friction or an air-controlled suction-wheel. A variation of this is palletized feeding. This is the case where an entire pallet full of paper may be placed on the feeding table. The second type is called "round pile"; this involves the sheets being placed onto a belt on a table or rollers, which takes it around the end of the machine and then each sheet is individually pulled into the machine by an air-controlled suction-wheel. The sheets of paper will be separated by help of blowing air between.

Paper Folders

Folding machines, exclusively used for folding paper, are commonly referred to as paper folders. These machines are typically used for creating letter folds (C Folds) and accordion folds (Z Folds). Other commonly used folds include a half fold, fold-out, double parallel fold, gate (brochure) fold, and right angle fold.

The fold type is set up by adjusting two folding plates. As paper enters the machine, it hits the first plate, is run through rollers that fold the paper, and hits a second plate, after which the final crease is made. Most paper folders allow for a wide range of fold types. Right angle folds require the paper to rotate 90 degrees. Many machines require manual re-feeding after the first fold to accomplish this.

Entry level paper folders require that the folding plats be adjusted manually, with fold settings specified on the folding plates. Higher-end paper folders will electronically adjust the folding plates for added precision and convenience. Both usually have fine tuning knobs for precise adjustments.

Most paper folders pull paper into the machine by use of a friction wheel. This wheel grabs paper by use of friction. Friction-feed paper folders do not work well with glossy paper as the friction wheel slips on the paper's surface. Pneumatic paper folders are ideal for folding glossy paper.

Pneumatic Folding Machines

Pneumatic paper folders pull paper into the machine by use of a vacuum. These folders are often referred to as air-powered paper folders. This makes it possible for the paper folder to be used with glossy or shiny paper. Most pneumatic paper folders include a built-in compressor. These folders still use two folding plates. The plates are adjusted manually or electronically, depending on the machine.

Folder Inserters

Folder inserters are designed for mailing bills, checks and other material. Folder inserters take paper, fold it, insert it into an envelope and seal the envelope. Folder inserters are available in several designs, many with multiple feed trays for several sheets of paper. Many have the ability of including inserts and return envelopes.These are mixtures of knife and buckle folders.

Folder Sealers

Paper folder sealers are used to fold special pressure sensitive paper. As the paper is folded, pressure rollers roll along the edge of the paper, bursting open tiny glue pockets that seal the letter shut. Pressure sealed documents are typically opened by tearing off a perforated side or tearing open the sealed portion of the letter. Documents folded and sealed do not require an envelope for mailing and are often used for mailing bills, invoices and other mailed documents.