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P is Perfect Binding
Perfect Binding is a binding method that utilizes adhesive to hold pages together at the spine of a book. Perfect binding, also known as adhesive binding, applies an adhesive to the spine of gathered pages which, when dry, keeps them securely bound. A cover is attached over the binding adhesive. Publications bound by perfect binding include paperback books, catalogs, and magazines. This method of binding is a low to medium cost.
There are six stages in a perfect binding machine:
Gatherer - after printing and folding, book signatures are gathered together in the correct sequence. At the gathering phase, any separately-printed inserts (such as advertising supplements, short sheets or subscriber reply cards, etc.) need to be assembled and included. Once signatures have been gathered together, the book-length pile of them is called a book block.
Backbone Cutter - in perfect binding, the signature folds at the spine need to be removed so that the pages align squarely with each other at the binding edge to ensure adhesion of the glue to the spine. The book blocks are gathered, spine down and are carried by clamps to the binding section. The spine protrudes from the bottom of the clamps, where knives, saws, or shredders cut off or grind away the signature folds. After cutting away the folds, the spine must be roughened. This improves the application of the adhesive. After spine cutting, the book block is ready for the application of the adhesive.
Gluer - while still clamped together, the book block is carried to the gluing station, where an applicator wheel forces the adhesive onto the spine. Most of the adhesives used in perfect binding are hot-melt adhesives, a mixture of resins and polymers which become fluid at high temperatures and dry by cooling back to a solid state.
Cover Feeder - After application of the adhesive, the cover is applied to the book block. A feeding mechanism scores the cover where it is to be folded around the book block, and the cover is pressed onto the backbone. Nippers pinch the cover around the spine, while clamps press the front, back, and sides securely around the book block. The bound book is then dropped onto a conveyor belt where it is sent for trimming.
Trimmer - Once the adhesive is cool, trimming around the outer sides occurs to create the final trimmed book.
