Digital Printing Postpress

A few years ago, people thought that digital printing was a new thing and there was still a long way from commercial production. The actual situation at that time was also true, because at that time, the quality of digital printing and people's requirements did exist a big gap, and the production efficiency was also very low, and it was difficult to meet people's demands.

However, the speed of digital printing changes and development is completely beyond people's imagination. Today's digital printing quality has become closer to offset printing, the production efficiency has been greatly improved, and the range of printing materials has become wider and wider. The excellent quality and printing effects of some printed products are even surprising. Digital printing has become one of the most attractive ways of printing.

However, from the point of view of binding and post-press processing, there is still a huge difference between the post-press processing of digital printing and the post-press processing of offset printing. This article attempts to discuss the difference in post-press processing between different printing methods in order to provide some references for digital printing practitioners.

Digital Printing Colorants and Offset Printing Inks

One of the biggest differences between digital printing products and offset printing products is the coloring matter printed on paper. The pigment used in digital printing has a completely different chemical mechanism than the ink used in offset printing. Digitally printed toners are dry when printed on paper, and then bond the toner to the surface of the paper by heating and melting the silicone oil. The offset printing ink is a liquid, which achieves the ink drying and the adhesion of the ink film and the paper through the balance between the solid color material and the liquid material in the ink.

The drying process of digitally printed toner on paper is different from that of offset printing ink on paper. When the offset printing ink dries, the liquid binder penetrates the surface of the paper, and the solid colorant and the partially dried binder remain on the surface of the paper; and the digital printing colorant does not penetrate into the paper. This difference reminds us that we must pay great attention to the post-press processing of digital prints because it may affect the quality of certain post-press processing. For example, when the offset film printing method that is often performed by offset printing is applied to digital prints, the surface colorant may cause the film to not recombine well. In addition, due to the effect of silicone oil, it also causes some difficulties in post-press processing. Many post-press processors have found that if there is a lot of silicone oil on the paper, it will lead to post-print coating and film coating difficulties.

Thinking about postpress processing from prepress design

The prepress design of excellent digital prints will contribute to the successful completion of digital printing and postpress processing. In digital printing, the prepress design has a great influence on the cost of postpress processing. Since digital printing uses a limited number of paper sizes and a large number of digital prints are printed on one side, the following factors should also be considered in addition to the prepress design that requires digital printing to make the most effective use of paper.

Paper orientation

Whenever possible, try to align the orientation of the paper with the spine of the finished book. Due to the particularity of the combination of the color material and the paper on the surface of the digital printing paper, the folding of the horizontal yarn in the direction of the fold is more likely to occur at the folding at the folding process. Therefore, when designing the post-press processing technology of digital prints, it must pay due attention to prepress design.

2. The position of the image on the sheet

In general, a large number of digital prints are designed so that the image is in the middle of the print sheet, but it is found after printing and sending to the postpress that this would waste a lot of money and time. For example, a 6-inch by 9-inch image is designed in the middle of a sheet of 8.5 inches by 11 inches. When cutting, the four sides of the sheet need to be cut; but if the image is placed on a sheet At the corners (for example, the upper left corner), only two sides need to be cut, thereby saving the post-press processing time and reducing the printing cost. But if the other two sides of the image are bleeding designs, you still need to trim all four sides.

Bookbinding and Postpress Processing Considerations

From the very beginning, it was carefully designed for India and India to ensure that printing and post-press processing were in harmony. The following points should be noted in production.

1. Folding

Since the color material on the digital print only stays on the surface of the paper, the folding is more likely to occur when the folding process is performed. Therefore, it is preferable to crease the fold before the folding process, in particular, the printed surface is printed with thick colors or printed paper. Crimp creases are particularly important when quantitation exceeds 80 lbs.

Laminated film

Laminating the surface of digital prints, especially after printing large areas on the ground, will help protect the printed materials during post-press processing, especially cutting or packaging. Because in the post-press processing process must be very careful to protect the printed sheet, otherwise, printing even better, because the post-press processing is not done will lead to waste and increase waste. It is not necessarily advantageous for the double-sided printed matter to be coated on one side because the non-coated side may be peeled off due to the frictional force during the subsequent processing.

3. Saddle stitching

Saddle stitching is a good choice for most digital prints, and it is particularly suitable for binding thin prints such as guides, booklets, and brochures. One of the keys to making the bookbinding economical and practical is that it can be processed on-line with other processing methods, and the post-press processing, which can simultaneously perform collation, folding, binding, and online cutting, can guarantee the fast delivery of digital printing requirements.

4. Set flat

When designing flat-boundary prints, pay attention to leaving enough bound blank space between the spine and the text. For example, if the O-spiral thread has a 3:1 ratio (3 holes per inch), then at least A 3/8 inch blank is provided; at a hole ratio of 2:1, at least 1/2 inch blank should be left. This blank refers to the distance between the edge of the line nearest the spine and the edge of the spine.

In order to clearly define the specific location of the processing, the designer is better to understand the change of the proof after the digital printing with the actual printing paper before the digital printing process, which is particularly important for digital prints. A large number of computer design programs do not consider slight changes in the thickness of the paper after printing, and the color material printed on the surface of the paper in digital printing causes the thickness of the printed sheet to change. When binding dozens of pages of digitally printed paper, the cumulative thickness variation may make the computer's carefully calculated binding sizes useless. Grasp the proof change parameters of the actual production paper after digital printing, in order to accurately calculate the thickness of the book in the design of printing, to ensure that after the printing process to obtain a suitable binding size.

5. Perfect binding

Like the offset printing of offset printing, the binding of digital prints must also consider the bound blanking. In addition to leaving a 1/8-inch milled back allowance at the spine, a 1/8-inch cutting margin must be set aside on the other three sides of the book. In addition, a 1/4-inch glue area should be left in the lower part of the book cover to prevent glue from seeping into the next book in the binding. Binding finishing also requires that the print should be printed a bit larger than the body's bleeding print.

6. Wireless glue binding

Whether you believe it or not, wireless glue binding is an important finishing method in digital printing binding. The key to the hardcover process is how to securely bond the book block to the hard case and produce books that can be stored for long periods of time. Although the cost and time required for the binding of a perfect binding may appear to be somewhat inconsistent with the digital printing for the short-run printing market, some post-print binding companies have already prepared different colors, different styles, and requirements for digital printing. Hardcover bookcases of different sizes are used by digital printers at any time. Therefore, wireless glue binding has become a common binding method for digital printing.

Integrated Finishing Solutions

The quality and speed of digital printing make it even more compelling, and it has become one of the increasingly widely used printing methods. Most digital prints require almost any form of binding or post-printing to become a practical printing product. It should be clear that most post-press processing processes can be applied to digital printing post-press processing, but not all printers or post-press processors can control the post-press processing of digital printing. If a company has a wealth of digital printing knowledge, understands the special nature of digital prints, and has a variety of post-press processing equipment, with strong production and processing capabilities and a wealth of post-press processing experience, then the digital printing of post-press processing It is no longer a difficult job.