Talking about the Control of Printing Quality of Color Newspapers (I)

There are many factors affecting the quality of color newspapers in the printing process of color newspapers, mainly including the restoration of color and levels of pictures, ink color, layout, registration, ink and ink balance, and the status of equipment. In actual production, we mainly control from the following five aspects.

I. Whether the colors and levels of the color newspaper pictures are well restored

The restoration of color and gradation of a picture is mainly related to two processes of scanning and printing. When scanning, the originals are sorted first (separated into fax pictures, photos, and quadratic originals). Scan the fax image and the original photo with the appropriate number of lines behind the aligned scanner lens. Pay attention to 4 points when processing the scanned image: 1) Ensure that the highlight part of the image does not stop netting; 2) Guarantee the darkness of the image Adjust the level of some levels are not combined; 3 as much as possible to ensure that the tone of the middle tone is rich, moderate brightness; 4 in the background color removal to ensure that the dark tone of the picture after the four-color overlay does not exceed 260% to 280%. For the second manuscript, in order to prevent "moiré" phenomenon from occurring during the printing process, the scanner lens must be properly blurred before scanning or the image of the scanned second manuscript should be properly decontaminated after scanning. Scanning accuracy or angle rotation is less than 15°, focus on a point to adjust virtual. In these processes, the scanning personnel's adjustment of the R, G, and B parameters of each picture is based on their own experience and the conditions of the printing equipment of the newspaper to judge their own processing results.

The production of Bao Mei, taking the Xinhua Daily as an example, Xinhua Daily has A, B, C, and D total of 16 color newspapers every day. Below each layout there is a standard color bar that is superimposed by four colors. The production of color bars includes two aspects: 1100% outlets mainly test hue and density; 230%, 50% and 70% outlets mainly measure printing outlets. We make this standard color bar with the following 3 functions.

1. In theory, when a person who prints a color ink just adjusts the color bar of the day to be close to a standard color bar, the amount of each color of the picture on the color bar is basically in place.
2. When the plate-making personnel adjusts the exposure time and the developer density, the exposure time and the developer concentration can be determined according to the dot condition of 3% to 4% of the highlight portion of the color bar.
3. The scanner can compare the difference between the effect of the picture above the color bar and the manuscript based on the sample report when the printing person adjusts the color bar near the standard color, and reflect on the R, G of the picture that he is dealing with. Whether or not there are areas for further improvement in the B-parameters, this can provide empirical data for scanning similar images in the future.

Second, the color of the text of the newspaper is whether the ink is even and the layout is smooth

In order to ensure that the text portion of the color newspaper is evenly colored and the layout is smooth, we require the operator to start with the following three aspects:
1. Make sure the film is clear and dense when exposed.

In the actual production process, due to the change of the exposure time, or the difference in the sensitivity of different batches of films, the characters on the exposed film are directly broken and the density is not uniform. At this time, the staff needs to take timely measures, or re-release the film, or take other remedial measures to ensure the quality of the film.

2. At the time of plate making, ensure that the PS plate is clear and uniform in density and the layout is flat after exposure and development.
In the production process, in order to produce a qualified PS plate, the staff usually takes the following steps: 1 Select a good table paper, to ensure that there is no scratches and dust on the surface of the table paper; 2 Use anhydrous water before using the table paper Alcohol will wipe all the paper; 3 check all the film for quality problems; 4 must ensure that there is no other sundries in the paper plate; 5 ensure a good suction, proper exposure; 6 to ensure the development of the work In good condition, there is no debris attached to the developer's glue stick. For the printing plate due to the inspiratory plate machine is not good, or there is dirt adsorbed on the table paper, resulting in a good version of the PS plate is not qualified when re-sun.

3. In the printing process, in order to make the layout of color newspapers uniform, uniform ink, clear text, print operators are usually required to proceed from the following aspects.

1 Make sure that the press roller has a moderate pressure. Under normal circumstances, the printing presses, the printing pressure between the rubber roller of the high-speed imported machine in the 0.25 ~ 0.3mm, the printing pressure between the rubber roller and the platen roller in the 0.15 ~ 0.2mm, the roller bounce allowed in the 0.01 ~ 0.03mm. If the printing pressure of the drum is too large, the strokes of the printed characters are thickened. If the drums are beaten excessively, it is easy to cause the printing of the layout and the ghosting of the characters. At the same time, there will also be the phenomenon of uneven paper feeding during printing.

2 Adjust the pressure between the various rollers of the printing press. Adjusting the pressure between the rubber rollers is crucial to ensure that the color of the printed newspapers is uniform. First of all, to adjust the gap between the ink core roller and the anilox roller (different models, the gap is not the same standard). In the actual production process, the gap adjustment is directly related to whether the entire ink-transfer process is good; next, the pressure between the anilox roller and the ink-transmitting glue and the respective ink-transmitting glue and the string-ink glue should be adjusted (under normal circumstances Large rubber rollers with a diameter of more than 120mm are imprinted at 7 to 8mm, and rollers with a diameter of 80 to 95mm are imprinted at 5 to 6mm); finally, the pressure between the inside and outside reliance and the platen roller is adjusted (usually internal repulsive The imprint on the plate is 1mm smaller than the imprint on the plate.)

3 Guarantee blanket performance. The flatness and good resiliency of the blanket are very important for ensuring the flatness of the newspaper and the reduction of the dot of the picture. The following points should be noted when using the blanket in the production process.
a, several indicators of the new blanket: blanket thickness, hardness, surface flatness and surface resilience. At present, the brand of blankets on the market is more complex, and even if it is the same brand, it is difficult to guarantee the specified technical indicators because of the difference in origin and price difference. If the thickness is not enough, the length can not meet the required size requirements, poor elasticity, surface unevenness and other direct impact on the printing quality of newspapers.

b, alternating use. When the new blanket is printed on the machine, its elasticity gradually decreases with the passage of time. If two blankets are prepared for each machine to be alternately used at regular intervals in the production process, not only the printing quality of the newspaper can be improved, but also the printing quality can be improved. The life of the blanket.

c. The blanket is selected according to the model and the machine condition. Currently, the type of machine used for newspaper printing is mainly Y-type and B-B-type. Because Y-type is two rubber rollers pressing a rubber roller, and B-B The structure is a pair of rubber roller pair pressure. Therefore, when selecting the blanket, it is necessary to consider that the hardness of the blanket is not the same. In general, the blanket used by the Y-shaped structural machine should be harder, which can effectively reduce the possibility of flowering in the 2 to 3 editions. In the long-term use of the machine, the roller pulsation is relatively large. Therefore, when selecting the blanket, it is necessary to select a blanket with a high hardness as much as possible, which can also reduce the degree of blooming of the plate.

4 Adjust the ink layer of the ink core to ensure that all ink keys perform well. At present, most printing presses used by newspapers are modern imported rotary presses. The adjustment of the amount of ink is accomplished through centralized control of all the ink keys of the machine. The adjustment of the ink layer is the most important step. The operator can effectively control the ink volume of all layouts on the operation console. The operator must first strictly and carefully adjust the original ink layer of the ink core roller to the specified data, and ensure that the ink core roller ink layer is evenly adjusted when adjusting. . The thickness of the ink layer is usually determined according to the thickness of the anilox roller pattern and the gap between the anilox roller and the ink core roller: for the coarse textured anilox roller, the ink layer thickness is set to be lower than the anilox roller. The clearance between the core roller and the ink core is 0.08-0.1mm. For fine-grained anilox roller, the ink layer thickness is set to be 0.03-0.05mm more than the gap between the anilox roller and the ink core roller.

5 The overall quality of the operator. The operator's technical content, sense of responsibility, and practical experience are the human factors that affect the printing quality of color newspapers. Operators with technical and practical experience can accurately and timely grasp the various processes, and at the same time, when color quality problems occur, they can be timely. Effectively identify problems and solve them. In addition, in the printing process, it is necessary to cultivate the operational responsibility of the operators, carefully and carefully adjust the ink color of each edition so that each layout is uniform in ink and medium in ink, and at the same time, the ink balance is always controlled during the printing process.