Prepress and its effect on printing quality

A piece of printed matter, when the designer is designed on the computer, we will proof for you, export the film, print the PS version, provide the printed version of the PS to the printing press. This process is commonly called prepress in printing. Prepress is an extremely important process in printing.

First, proofing

Proofing is divided into traditional proofing and digital proofing.

1, traditional proofing

Traditional proofing is actually going through the whole process of printing first, printing out several proofs to provide to customers. It must first output the film, out of the PS version, and then use the proofer to make a few proofs. The proofer is actually a semi-manual printer.

The advantages of traditional proofing are: 1 You can make monochrome proofs. Because in the past, printing color was printed on a monochrome machine. What kind of printing should be done? We must wait until four colors are printed before we know that if there is no monochrome proof, it is difficult for the printer to grasp the size of the ink. Of course, with the development of printing, four-color machines are now printed, and monochrome proofs lose their meaning. 2 Traditional proofing is printed with ink. More intuitive for customers.

The disadvantages of traditional proofing are as follows: 1 As traditional proofing needs the prepress and printing processes that are the same as formal printing, it has issued a film. If customers need to modify it, they must come back again, so they often cause waste. 2 The proofing machine used for traditional proofing is semi-manual, one by one, so the control of the amount of ink and the grasp of color depend to a large extent on the level and feel of the personal proofing master. For example, if the proofer prints a solid sample, the amount of ink may be very large, and the ink layer printed is very thick. However, the printing press is high-speed printing, and its ink volume can only be according to the standard, and the pasting paste can be used. 3 Low efficiency of traditional proofing.

2, digital proofing

Digital proofing is a new proofing technology that has matured with the rapid development of computers.

As far as equipment is concerned, digital proofing is the same as general ink-jet printing, but the accuracy of printing is higher. In fact, they are essentially different.

The difference is that, first of all, digital proofing computers must have color management software installed; followed by a well-designed document, digital proofing, which, like the output film, must be interpreted with RiP before printing. To put it plainly, digital proofing is essentially the use of a large-scale, high-precision inkjet printer to print proofs that closely resemble the colors of prints. In order to approach color and print, color management software must be used in advance to accurately print color corrections. Files to be proofed are explained by RiP, and then printed, and printed colors are used to simulate real prints.

Second, the paper used for digital proofing is special. As we all know, the same graphics and text are printed on different papers, and the sense of color is not the same. Digital proofing is inkjet printing, where the effects of color change on different papers and the effects of ink printing on different papers vary. Nowadays, there are many kinds of paper, so digital proofing can only use the printing effect of the most commonly used coated paper as the simulation object, but the proofing is still a kind of paper similar to photo paper.

At this point, we can see that digital proofing has the following advantages:

1 Color simulation is true, eliminating human factors.
2 cost savings. Because digital proofing preceded the output of the film, it was just as phototyped and the document was explained by RiP. If there is a problem with proofing, the output of the film will also have problems, and vice versa. Proofing If you find a problem, you need to modify it without increasing the cost. In most cases, with some minor changes, we do not need to make proofs twice, so we will not increase costs.
3 fast and efficient. The whole process of digital proofing only needs to be processed on the computer and does not need to go through the whole process of printing as the traditional proofing.
The disadvantage of digital proofing is that because it is analog printing color, there is still a difference between print and print. In addition, it cannot display the printing effect on specialty paper.

Second, the film output

Several Factors Affecting Film Quality in the Process of Film Exporting .

1. People's Factors In general, designers of design companies lack a deep understanding of printing. In the process of design, they are pursuing the beauty of creativity and layout. They handed over the design documents and the color drafts to the printing factory, which is responsible for the printing factory. This is also in line with the division of labor in the modern society.

As already mentioned, the documents used to output the film need to meet certain requirements. In addition, the film exporter needs to understand the printing process requirements, post-press processing, binding, etc., and fully take into account the process requirements of the subsequent processes in the imposition, so as not to print things out, only to discover that this is not possible. It is difficult to do. In addition, for the documents provided by the light designer, since the design draft must have been repeatedly modified, some invisible error messages are often hidden in the layout. These error messages are often displayed when interpreted by RiP. Come out, causing the issue of film problems. Fussen is black and white, and some errors are not easy to detect when the film is inspected.

Of course, if a digital sample is printed before the file is distributed, the problem will be obvious. However, in today's low-profit era, many customers rely on and trust our film exporters to save costs, and they often avoid proofing. .

In the general photocopying center, you go to export the film. The quality of the film needs to be checked by yourself. If there is a problem, you have not checked it out and printed it in the printing factory. The printing factory will not be responsible for this. The photo center will also state in advance that if there is a problem with the film, if they are the responsibility of the film, they will reissue it for you for free, but they will not bear the joint and several liability arising therefrom. To be honest, now that a film has been issued, the profits have been minimal. Once you print, there will be a lot of paper money. If you want to pay for the losses caused by the center, no one dares to open the center of the photo.

2, software, equipment, raw material factors

The photocopying software used by the photocopying centers is different. Of course, there are currently pirated copies on the market. Even if Founder Software has a large amount of pirated copies.

The level of pirated software is indeed shocking, but I think it is still untrustworthy because it is "theft." When pirates decrypt genuine software, they often ignore some of the programs; Founder companies will continue to improve the software they develop, and some of these defects will be remedied, while pirated software will not be upgraded. Therefore, pirated software often makes mistakes in interpreting files.

So far, the image-setters for outputting four-color films have been imported, and are mainly concentrated in several brands. The output of film quality is guaranteed in terms of equipment, but the maintenance of equipment has a great impact on the output of films. Because the image-setter is essentially a precision optical instrument, the tiny dust on the light source and the prism and the lens directly affects the quality of the beam that scans the film, thereby affecting the quality of the film.

In fact, at the center of photocopying, the biggest difference in the quality of the film is the quality of the original film, which is also the most important cost in photocopying. The price gap and quality difference of various film films are self-evident.

Third, printing version

The principle of printing machine, it is very simple to say, is to close the film and PS version, and then exposed to ultraviolet light.

Here we can see that there are two main factors affecting the quality of the printing plate: 1 vacuum, the tightness of the film and the PS plate. 2 light source, UV wavelength within a certain range, as far as possible "pure."

Ordinary printing machine and imported high-end printing machine is very different. In terms of price, a printing machine commonly used in general printing factories is between ¥6000 and ¥15,000, a Taiwan-made printing machine is between ¥6 to 80,000, and a German brand-name printing machine is in the ¥ More than 130,000; on the vacuum, the general Shai Banji vacuum pump, imported Shaibanji compressor; In order to make the film and the PS paste used by the difference between the blanket and glass is also very large, the price is: Germany imported original rubber About 2 million cloth, domestic blankets only ¥ 300 ~ ¥ 400. As far as the light source is concerned, the original fluorescent tube of the German Tianma is ¥4200/piece, and the domestically-made light tube is ¥130/piece. These will not be detailed one by one. In addition, the high degree of automation of imported printing plates to determine the exposure time, for example, the domestic Shaiban machine with the passage of time, need to artificially lengthen the exposure time, and imported printing machine in the first use of a certain brand PS In the case of media, set an appropriate exposure time, and later do not need to change, because it is equipped with a "light flux detection" device, with the lamp is automatically different to determine the exposure time.

After the PS version was exposed, the next process was development. Most printing plants now use manual development, and some are developed using an automatic processor. The use of fully automatic developing machine development is not only for efficiency and reduce the workload of the printing staff, the main purpose is to control the quality of the PS plate. Because the development time of manual development is determined by the printer, the automatic processor is controlled by the machine.

Regardless of what type of printer is used, manual development or automatic development, a PS version that finishes the printing is obtained. With regard to the finished PS version, the layman cannot see the difference, but the difference is substantial. To check the quality of the PS plate, we use a 50x magnifying glass. Good PS version, exposure, development just right, outlets full, complete. In the past, printing professionals generally told you that 5% of outlets could be printed out due to the limitations of printing plates, developing equipment and printing presses used in their factories. Today's technology and equipment, 2% outlets can also be well displayed, printing equipment can also be a good 2% print out. When the copy of the PS version is better, the impression given by the print is that the picture is rich. For example, when you print a portrait, the person's face has a high point of light (the brightest point). If the quality of the plate is good, the point where the high point of light goes deeper is a uniform transition. If it is a big highlight, it means that the highlight The small outlets around the point have been lost in the process of plate making and printing...

Nowadays, there are more and more merchants producing PS plates, and the price and quality of various PS plates are very different. It directly affects the quality of PS plates.

Fourth, punch

A good PS version can not be directly provided to printing presses, because we know that four-color printing presses, four-color must be accurate, so when loading the PS on the printing cylinder (printing term hanging Version) must be basically the same in order to reduce the workload of calibration (commonly known as version). Therefore, we first made a hole in the PS plate (commonly known as the positioning hole) and stuck on the press plate clamp, so that the calibration is more convenient.

There are two ways to punch a PS plate:

1 Punch holes before printing. After the PS version hits the hole, when the film is attached to the PS plate, the relative position of the film graphic and hole is guaranteed. Most printers use this method. Obviously, this method is due to the fact that people use ordinary rules to set the film position, and the error is very large.

2 First paste the film on a fixed position on the PS plate. After the plate is cured, use an automatic positioner to punch the hole. Here we can see that after the PS version of the sun is good, the relative position of the graphic text, up and down, left and right in the PS version must have errors. However, the automatic punching machine is facing the graphic line of the graphic version again, setting the hole position, and then punching the hole. At this time, the error is very small (because if the graphic and text is oblique, the hole will follow the slant and hang on the printing press. of).

From the above it can be seen that a print must achieve high printing quality, not only the printing press, but also all aspects before printing.

Good prints are the result of meticulous and pursuing perfection in every process. If the procedures are so careless, the error will accumulate. "Worse in the slightest, be a thousand miles away," and in the end it will be a rough print. Our slogan is: perfect quality, starting from the details... This is not a generic slogan but an objective requirement for the specificity of printing.

Source: PACK.CN