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Technical specifications - post-press

 

BINDING

 

Saddle Stitching

Cover Feeder

In the procedure of applying covers to saddle-stitched books, the cover falls from a hopper into a rotary feeder and is scored for accurate folding before being jogged for proper alignment and then pressed against the backbone of the book.

Stitching

The term "saddle" derives from the SADDLE of the machine. The machine cuts the wire, forms the staple, drives it through the paper and clinches it from the other side. The section is stitched in two or more places depending on the height of the publication. The number of pages that can be satisfactorily stitched in this manner depends to a great degree on the number of pages and the thickness of the paper. Saddle stitching, is fast and, therefore, more economical than PERFECT BINDING. The staples used in saddle stitching are formed from round wire and are generally made of stainless steel.

 

PERFECT BINDING

Perfect binding offers several advantages over saddle stitching. The backbone of the wraparound cover can be printed with the name of the book for easy reference when stacked on a shelf, and the books can be bound in one continuous operation from signatures to finished product. Another important advantage is that single sheets can be added to a publication without needing a centerfold, which is required in saddle stitching. Modern glues and gluing methods produce permanently bound books.

The strength and durability of perfect-bound books has increased with improvements in machinery, binding edge treatments, and adhesives.

Perfect binding takes place in a finishing line consisting of a gatherer, backbone cutter and roughener, gluer, cover feeder, trimmers, and counter stacker.

Gathers

Gathering is the operation of assembling signatures on top of each other in proper page sequence. Gatherers accept printed signatures delivered from a web press, which folds them inline, or from stand-alone folding machines. The gatherer has a separate feeding station (pocket or hopper) for each signature.

 
Backbone Cutter and Roughener

The book block travels along a spiral raceway that jogs and turns it from a horizontal to a vertical position. Now standing on its spine, it enters the adhesive-binding section of the perfect binder, which has continuously circulating clamps that close over each book block with a vise-like grip. While held in the clamps, the backbone edge of the book extends at least 3.5mm below the bottom of the clamps where the signature folds will be milled off and roughened in preparation for gluing.

Knives or saws on milling or shredding units cut off or grind away the individual signature folds so that each sheet is exposed for roughening to better accept and absorb the adhesive.

Gluer

Still clamped together, the book block reaches the gluer, or gluing station, which typically consists of a single glue pot with two applicator wheels. The applicator wheels force the adhesive into the exposed paper fibers, and a rotary spinner controls the thickness and uniformity of the glue coating as it meters the glue along the backbone to a thickness of approximately 0.020-inch.

Cover Feeder

In the customary procedure of applying covers to perfect bound books, the cover falls from a hopper into a rotary or stream feeder and is scored from one to six times, then jogged for proper alignment before it is pressed against the glue-covered backbone of the book block.

Nipping stations pinch the cover around the glue-coated backbone while two plates clamp it at the score line and press its front, back, and sides against the spine of the book block. When the book block is unclamped, it drops onto a conveyor completely assembled but for its closed signatures that must be sliced open on a trimmer.