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Sealed with a thread

Mar 1, 1996 12:00 AM

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In spite of its name, perfect binding is not always the perfect way to bind the pages of a book. The main drawback with this finishing procedure can be found at the signature stage. Unless the pages of each signature are sewn together, a process that for many projects is prohibitively expensive, the strength and durability of a perfect bound book often leaves much to be desired.

Twenty years ago, the Brehmer Co. in Leipzig, Germany devised an effective solution. Using its expertise as a manufacturer of book binding equipment, Brehmer developed an economical alternative to sewing called thread sealing. The method involves stitching or stapling the spine of each individual signature with a plastic-coated thread, then sealing the threads with an application of heat. The result significantly improves the strength of each signature destined for perfect binding by using a procedure that's both quick and cost effective.

Although thread sealing has continued to grow in popularity throughout Europe, Asia and Australia since its development, its use in America virtually is unheard of. That situation began to change last year with Stahl's acquisition of the Brehmer works.

The arrival of the procedure in America comes at an opportune time, as the popularity of perfect bound books is on the upswing. Other advanced perfect binding materials and techniques, such as the use of Otabind covers and the development of advanced adhesives, have advanced the state-of-the-art in technology.

On the market end of the equation, computer hardware and software manufacturers increasingly are turning to perfect binding to finish their manuals and tutorial guides.

Even with recent advancements in perfect binding, the finishing process still is dependent on a number of variables that can adversely affect the durability of the resulting book.

Paper type and the quality of the book's stock influence how well signatures stay together once assembled. Ironically, a better or heavier stock might present more problems than a lighter variety due to its rigidity.

The quality, type and viscosity of the adhesive used in the binding process can determine the life span of the completed book. As adhesive deteriorates, so does the book's durability. The way the adhesive is applied also affects staying power, both long-term and short-term. The faster (and less carefully) the adhesive is applied, the faster the book will deteriorate.

The roughness of the cut-off spine of a signature or its notch perforations are other problems. Such built-in imperfections could work like a saw against the lining strip of a perfect bound book, eventually destroying this main structural component.

The quality and type of lining strip and cover also can have an adverse impact on longevity. All elements of the binding must be compatible to function correctly, and striking that balance sometimes is more of a hit-or-miss art rather than an exact science.

Finally, the precision of the drying and pressing process can determine if a book will emerge as a useful unit or a conglomerate of loose pages in a few years or months time.

The most effective way to dispense with the variables is to sew the signatures of the book together with a book sewing system. While that procedure is the solution for higher quality perfect bound books, it is not economically viable for production of such volumes as mass market titles, children's books and computer manuals.

This is where thread sealing enters the equation. The system works with any brand or type of paper folding machine that can feed signatures, thereby minimizing the capital investment involved. However, in spite of its affordability, thread sealing produces a book with approximately 70 percent of the strength of a sewn volume. More significantly, a thread sealed book has more than double the strength of a perfect bound book.

Another advantage: thread sealing provides end users with a book that lays flat. That is a key advantage in the production of software guides and other types of reference materials that need to be opened to a particular page as the reader follows the instructions.

Although thread sealing offers several advantages, the systems that traditionally have been used for the procedure often left much to be desired. The machines were difficult to set up by all but the most experienced operators. Exotic paper paths often were fraught with potential obstacles where jams and skips easily could occur. Finally, these units were slow, somewhat negating their cost-effectiveness over signature sewing systems.

Use of digital control electronics and a more streamlined approach to thread sealing have combined to overcome past drawbacks. For example, makeready times on some machines have been reduced by 50 percent, making the process cost competitive for shorter run jobs and cutting production time on long runs.

One of the biggest improvements in thread sealing technology involved removing the integrated former folder from the system. Research revealed that, rather than contributing to efficiency, the built-in folder was thread sealing's weak point. This was where paper build-up and stoppages were most likely to occur.

By making the final fold an off-line procedure, engineers were able to map out a straight-through horizontal signature flow throughout the system, one with considerably less potential for traffic jams. Final folding becomes an outboard process, via the attachment of a buckle or knife folding unit.

Of course, regardless of the new efficiencies offered by state-of-the-art thread sealing systems, not all perfect bound books should be thread sealed. However, thread sealing will offer the printing facilities and binderies that use the technique a point of differentiation over their competitors.

The Stahl Brehmer FS 100 thread sealer, which is distributed in the U.S. by Heidelberg, features a top production speed of 328 feet per minute. That system features Stahl's PLC guidance system that leads operators step-by-step through all makeready and operating procedures, while monitoring travel through the machine. The unit takes up 40 percent less space than other machines, and is much lighter than units with integrated folders. The system reportedly can easily be moved into and out of a production loop, freeing the folders it works with for other duties.

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