Perfect Binding is book binding in the style of paperback books, telephone directories, magazines etc where only a short useful life is expected. Single leaved or folded sections are gathered / collated into book blocks that are fed either manually or automatically into a clamp which holds the book firmly. The perfect binding process then begins by "milling" the book spine to a rough edge, EVA hot-melt glue is applied to the spine and along the front and back edges. A creased cover is then applied and pressed firmly from below and from the sides to give the completed book its characteristic square back finish. Lastly, the top, tail and fore-edges are cut to size ideally by a three knife trimmer.
Drawn-on or Soft Cover binding is a repeat of the above process but the book blocks have been pre-sewn on a book sewing machine and the spine milling unit is switched off as it is not necessary. This process gives a stronger bind and is popular for school or trade reference books where a useful life of more than one year is required.
PUR glue is also used for a stronger, longer lasting bind or where a lay-flat book is required. This glue requires a longer curing time before three knife trimming can take place. The melting unit must also be enclosed in order to preserve the glue and prevent harmful fumes escaping. It is also more expensive than EVA glue but a thinner film thickness is required.
Saddle Stitching is the way most booklets and magazines are bound - wire staples hold the piece together through the spine / centrefold. The machine gathers together the printed and folded sections in the right order, with or without a cover, and then drives the required number of wire stitches through the centerfold where they clench. The stitched product then passes into a trimmer where the three open edges are trimmed to the finished size. Saddle stitching lines may also be equipped with a compensating stacker which stacks a pre-set numbers of items, turning the pile as it does so to form an even pile.
A saddle-stitched product lies almost flat when opened. Saddle stitching is a good choice for binding documents of up to 64-80 pages, in multiples of 4, depending on the paper bulk. Products involving more pages or of very thick bulk demand some other type of binding such as perfect binding.
Case or Edition binding produces hard cover books. It involves sewing or gluing the individual signatures together, flattening the spine, applying endsheets and a strip of cloth to the spine. The pre-formed hard covers (cases) are then attached. The spine of a case-bound book is typically rounded and there are hinges (grooves) along the edges of the cover near the spine. Case bound books sometimes also have dust covers or jackets.
Case Making is the process of gluing the cloth (or printed paper) over the boards, turning the edges and making a finished “case”- usually consisting of 3 board pieces.
Casing-In is the process of applying the cover onto the formed book block. Glue is applied to the front and back end sheets and pressure is applied as the case is fitted to the book.
Book Sewing (often called Smyth Sewing) is a process whereby thread is sewn through the spines of folded and gathered signatures connecting one to another. The threads are woven along the entire length of the spine, head to foot, for uniform strength and appearance. A cover material, such as thick or laminated paper or gauze, is affixed to the spine with glue and then the sewn book block may be perfect- or case-bound to complete the binding process.
Sewn books are extremely durable, withstand prolonged stress and can lie completely flat, making them easier to read and write in. It is not possible to remove a page from a sewn book without destroying the integrity of the binding and therefore sewing is ideal for bound legal & scientific books, documents and notebooks.
Twin Loop or Wire-‘O’ Binding holds the covers and pages of a document firmly in place by a double-loop wire inserted through holes drilled in their left edges. The wire is pre-formed, and open as a 'U' shape, the leaves are threaded over the wire loops and the wire is then compressed to 'close' the wire. The wire can only be closed once and therefore when in place, if changes are required, the wire is taken out and new wire used.
All of the document's pages lay flat when opened, can turn easily through 360°, and stay in perfect registration with adjoining pages. Wire-O bindings are frequently used to bind reference books, reports, proposals, and calendars. For wire bound wall-hung calendars the binding wire is in two pieces either side of a hanger, which has a matching 'thumb cut' cut into the page
Spiral Binding uses a continuous spiral of wire or plastic that is wound into the article being bound. It is most commonly used for the production of very thick price lists, road atlases, reference manuals and training manuals. One cannot add pages to documents once they are spiral bound, but pages from spiral bound documents cannot come undone from the binding.
The application of spiral binding is more limited than for wire binding and therefore is not common.
There are three main types of folding machine: Buckle or Plate, Knife and Combination.
Combination folders use buckle and knife fold units together.
Buckle Folding: A buckle folding station consists of three rollers and a buckle plate. The first two rollers are arranged vertically above one another and their job is to carry the incoming sheet into the buckle plate until it reaches an adjustable feed guide stop.The sheet is delivered into the buckle plate at a speed determined by the characteristics of the paper. As the lead edge of the sheet strikes the feed guide stop, the sheet continues to be fed into the buckle plate, creating a buckle in the space between the three rollers. As the excess paper drives downwards it is grabbed by the rollers and the fold is formed as the sheet passes through them.
Unlike knife folding, buckle folding is not restricted to any cyclical movement, which makes it ideal for high-speed folding. Each folding station can fit up to six buckle plates, arranged alternately above and below each other, allowing for a large number of fold variations.
Knife Folding uses a vertically moving knife and two rollers rotating in opposite directions. The sheet is carried from the feed to the folding station until it makes contact with the sheet stop. At this point, the knife descends vertically, plunging the sheet between the rollers that have been set to the thickness of the sheet going through them. As the sheet passes through the rollers, it is pinched and the fold is formed. This folding process is dependent upon the repetitive action of the knife.
Only one folding knife is to be found in any one folding station. For every subsequent fold, it is necessary to have a further knife folding station at right angles to the preceding one. Printers and binders specializing in folding large sheets usually use knife folders.
Folding Machine Feeders - 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 or Continuous. 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.