Folding ( it. German "fold") in the printing business - the process of folding sheets in a notebook of a certain volume and format in compliance with the sequential arrangement of pages in a folded notebook to obtain book and brochure publications. The fold line itself is called the fold .
By the number of folds, folding is one-, two-, three- and four-fold (notebooks are formed in 4, 8, 16 and 32 pages , respectively); according to the mutual arrangement of successive folds - parallel (each subsequent fold parallel to the previous one), perpendicular (each subsequent fold perpendicular to the previous one) and combined (partially parallel folds, partially perpendicular).
Often for paper weighing more than 170 g / m² and cardboard folding, a creasing operation is preceded to maintain an acceptable appearance of the product at the fold. If there is a die in place of the fold, then scoring is advisable to use when using less dense papers, otherwise the paint will crack on the image. This is especially true for matte coated paper.
Also drawing drafts of A2 format and larger are often folded.
Folding machines
For the folding process, use the appropriate equipment - folding machines.
The most common at the moment are cassette and knife folding machines designed for in-line production, that is, folding of products in large quantities. The folding process is as follows: the sheet passing through the first pair of shafts enters the cassette abutting against an adjustable stop, then pushed by the shafts, it bends under the action of its own elasticity, forming a loop that is captured by the next shaft adjacent to the lower shaft of the first pair and pulled to the next cassette, located opposite the first one, etc., depending on the number of cassettes. If one or all of the cassettes are closed, then the sheet, resting on the plug, unfolds on the lower shaft of the corresponding cassette and passes further and so on to the output shafts.
Output shafts are the last pair of shafts located separately from the folding shafts, but rotating with the rest. A perforating knife is installed on the output shafts for better perpendicular folding. Perforation violates the density of the paper in the folds, making the fold more clear and avoiding wrinkles around the fold. This happens on thick paper more than 115 g / m² because when folding the sheet two or more times, the density increases and the outer pages of the folded notebook are shorter and narrower than the inside, and the perforation removes excess density and the sheet simply folds in half again. For perpendicular folds, additional transverse attachments with cassettes or additional built-in units with knives are used, depending on the design features of the machine. The configurations may be as follows:
- 4 cassettes + 4 cassettes + knife (prefix);
- 6 cassettes + knife + 4 cassettes (prefix);
- 4 cassettes + knife;
- 6 cassettes + knife;
- 4 cassettes + 2 knives, etc.
Literature
- Folding // Publishing Dictionary Dictionary: [electron. ed.] / A.E. Milchin . - 3rd ed., Rev. and add. - M .: OLMA-Press, 2006.
- Folding - an article from the Great Soviet Encyclopedia .