Folding Machines and Methods of Folding - P Sajith

As a Folding machine supplier, I keep getting a number of questions on the various types and models of paper folding machines. I have seen that at many a times, a user picks up a model without understanding what it can not do!
The criteria followed by such buyers, in particular the “used” ones, are mainly (a) Brand and (b) Paper Size handled. A lot of other crucial factors are to be considered before zooming in on a specific model. These include (a) Type of Feeder (Pallet, Flat Pile, Vertical, Round etc. In small format machines, you also have friction and various types of suction feeders.) (b) Whether all buckle Or combination (c) Number of folds
(d) Direction of fold (left hand / right hand) (e) speed and the list goes on and on.
Most of the printers look at folding machine as just “another” type of machine used for folding sheets. But an automatic paper folding machine is a complex product with thousands of components and hundreds of variants. It has to address a variety
of problems , be it paper , print or fold related. It is the first link of a post printing chain in book production and hence needs to be treated with a lot of respect.

Modern day folding machines have extended beyond ‘simple folding’ and merge into the realm of packaging, mailing and so on. You can finish a complete booklet of 8/12/16 pages by either gluing or stitching and then trimming on-line.

We will understand some critical factors that define the specifications of a folding machine. You may kindly send us your specific questions that can be answered subsequently.

Speed : Folding machines of various capacities exist and are capable of folding sheets at much faster than by hand. Speeds are measured in meters per minute (instead of copies per hour), since the smaller the sheet size, the more copies can be folded in a given time. The capacity of a folding machine is also affected by the number of folding units it has. So if any one says that the machine has a speed of 10000 sheets per hour, ask him/her about the sheet size and the number of folds.
Folding machines are normally fitted with automatic feeders. Different thicknesses of paper stock and any alteration in the size of sheet require adjustment to both folding and feeding mechanisms. We will discuss various types of feeders at a different occasion.
We will deal with the most critical of them all first:

Methods of Folding: The methods by which sheets are folded by a machine can be classified into three.

1) Knife principle - where the knife folder accepts the long edge first. Figure 1.a shows the knife-folding principle. A vertically descending knife pushes the sheet between two contra-rotating rollers.

2) Buckle principle – where the buckle folder accepts the short edge first (this is more commonly seen). Figure 1.b shows the buckle-folding principle. The principle involves 3 rollers and a buckle plate. The first two rollers, one arranged vertically on top of the other, leads the sheet into the buckle plate till the leading edge of the sheet hits the buckle stopper. The paper bends (buckles) and sags between the rollers. This is picked up by the contra rotating rollers (placed side by side, arranged horizontally). You can have a number of buckle plates in a folding station for multiple parallel folds (eg. Accordion fold)

3) Combination - Knife-folding machines are uncommon and have largely been replaced by combination folders. The style of folding used varies from the basic right-angle folds, to the multi-stage machines employing mainly parallel styles. You can have knives after buckles and again a buckle and so on. Combination folders are specific to a set of jobs that can be done using them.


Buckle-folding machines (also knows as plate folders) are considerably faster than knife machines due to a more continuous process of operation. This is because, on a knife folder, the sheet must be halted at each folding stage before the knife descends to complete the operation, which also demands that the feeder coincides with the knife movement.
The buckle system is ideal for parallel styles of folding. One can have a multiple stage (all buckle) system, where paper is turned at right angle after each stage. Thicker sheets are not really suited to right-angle styles. Accuracy can be improved by the use of pre-creasing units fitted on the folding machines. Beyond certain thickness, one will need a knife unit to accomplish the fold.
Perforation should be made before the fold wherever possible except when folding lightweight papers which may tear while perforating. As the perforation is always made during the fold preceding the fold which will be made along it, the first fold cannot be perforated. Buckle folders can also slit a sheet after the first fold, the two sheets thus created following each other through and ending up as separate folded sections.

Combination-folding machines employ both buckle and knife systems and, though not as fast as all-buckle machines, are very versatile. They can handle both parallel and right-angle styles and are ideally suitable for book signatures. They are effective for folding signatures with sections having both parallel and right-angled styles. The first stage is normally buckle and the later ones knife-folds, thereby maintaining accuracy despite the gradual increase in the bulk of the work.