Give full play to the advantages of commercial rotation printing

In the printing industry in modern China, commercial rotation printing has taken off. The launch of the commercial rotation machine actually increased commercial printing to a higher level. It adapts to the requirements of the modern printing market with shorter production cycles, large quantities of printed products, and high quality, efficiency, and efficiency. With the standardization of work environment and machine operation, quality control of prepress production plays a decisive role in rotary printing. If the preparatory work is not in place, prepress production is not suitable for commercial rotary printing, which will result in a delay in the authenticity rate and a large amount of paper waste, which will seriously affect the printing quality and timeliness of its products. To make full use of the advantages of commercial rotation printing, prepress production that meets actual needs is indispensable.

one. Prepress production process

Design

High-speed commercial rotary machines generally use web printing. The paper path is relatively long. The physical and optical properties of the paper surface are not very uniform. The drying is mainly used to speed up the ink drying. There are different requirements for the prepress design from offset offset and newsprint offset. .

(1) Use of Ash Component Alternatives:

GCR (abbreviation of G rey C omponen t Replacement) refers to the non-color value of the multi-color area superimposed or mixed with the three primary colors ink in the color image reproduction, and can be replaced with the ink color equivalent to the weakest color in the three primary colors. And get the same visual effects.

In the actual production process, sometimes some supermarket sales of commodity alerts (DM single) ink is difficult to adjust, especially the large area of ​​the dark tone or the field part, the reason, in fact, Y, M, C version is too heavy, it is difficult to achieve Neutral gray balance, after many times through practice, found that Huang, Pin, Qing colored version are all deep, not only the ink is difficult to print uniform, easy paste version and is not conducive to register. In the front-end production must use GCR technology, increase the depth of the black version, use black instead of neutral gray, reduce the amount of ink used in other colors, so that when printing, as long as the black version is normal, the other color version is used with subtle ink Fluctuations and colors of prints are also very stable. These are mainly due to the role of the black version of the skeleton. By reducing the amount of colored ink, it is not only easy to meet the proof requirements, but also reduces the production costs.

(2) Use of Undercoat Removal

Under Colour Removal (abbreviated as UCR) is different from the above-mentioned GCR. GCR is a non-color structure process, it is a full-step background color removal, and background color removal is a partial removal. The black version is a short version. .

In commercial rotary printing, sticky inks, ink piles, headlines, or on-the-spot virtualities often appear. On the one hand, these phenomena cannot exclude the printability and equipment factors of the used paper and ink, but in part the reason is that the prepress design is not Good combination of actual production requirements for printing.

The reason that the pre-press design causes stickiness is the sum of the picture tonal value, that is, the total amount of ink is set to be unrealistic, and the sum of the cold-setting ink tone values ​​without drying specifies that the sheet of paper does not exceed 260%, while the thermosetting Web printing does not exceed 300%. Many people do not understand this, only the pursuit of full color, the sum of the tone value set very high, resulting in the use of the field of the heading or large area of ​​the dark tone part of the piled ink, hair imaginary, ink thickening also requires drying temperature The increase in the number of folds on the surface of the printed product has increased. And in the case where the sum of the tone values ​​is high, such phenomena as overprinting, backside printing, and backside smearing due to insufficient drying of the ink may occur.

Unnecessary waste of ink, paper, etc. Prepress production should use plate scanning. It can control the color difference between the print and the design in a smaller range.

Generally, the plate scan can reach about 80% of the normal amount of ink needed for the actual printing, and then through the adjustment of the overall ink characteristic curve, the genuine product can be rapidly produced, and the working efficiency can be greatly improved. For those who have not proofed The printing work is particularly important. The printing plate scanning work is more effective on those short prints with proofing. It can greatly shorten the time for the commercial ink machine to open the normal ink, and saves a lot of paper and ink and other raw and auxiliary materials. Enterprises reduce costs and increase profits.

If you come across the curve and the actual results, make sure the printing plate of the commercial rotary machine is thinner than the plate of the stencil printer. Increase the exposure time. In the case of 175 lines/inch screen, FOGRA1982 test strip Continuously dense

In the course of continuous printing practice, effective solutions have been found:

1. Reasonably set the sum of picture gradation values ​​as much as possible below the national standard value, so that the printed image can have both the level and the sharpness, and at the same time, the ink drying time can be shortened so that the printing product is not easily sticky.

2. Reasonable use of ground color removal. Partially remove the background color, reasonably control the neutral gray balance, increase the image contrast, and increase the saturation. This will effectively ensure that the pictures are colorful and not easy to pile up and dull. Considering the network expansion of commercial rotation printing, replacing the field with about 90% deep network is very effective for solving the problem of headline or color cast.

2. Printing plate drying

The commercial rotary press uses a soft and soft design where the blanket cylinders are each an impression cylinder. The paper completes the ink transfer under the blanket cylinder, and the dot expansion (mainly the mechanical dot expansion) is better than the sheet-fed offset printing press. It is much larger. It is detected during multiple printing processes. For different papers, taking into account mechanical and optical dot gains, X-Rite 528 optical densitometer is used to measure the normal start-up printing of Heidelberg M-600. Usually 13% to 19%. When printing plates used in commercial rotary machines, increase exposure and expose 3% or less of the dots.

Mechanical dot gains are affected by many factors, such as: ink, fountain solution, blanket, paper surface properties, etc. The main reason for the increase of the optical dot is that the refracted light increases the apparent area of ​​the dot. Because the area of ​​the dots will have a certain influence on the balance of grayscale and various colors of the printed matter, the 13th-grade stepped section will fade away from the third grade, and the yin-yang micron concentric circle coil section will correspond to the 8 μm yin-yang line. If it is not 175 lines/inch, it is necessary to make reasonable adjustments according to the actual conditions of each printing factory.

3. Plate scanning:

Commercial rotary presses have a fast printing speed, and before they reach normal ink color and registration, there will be a lot of scrap and defective products. In order to increase work efficiency, qualified prints appear as soon as possible, and the difference in the normal ink-printing curve between printed products is reduced at the time of printing. Generally, the following aspects should be checked before printing:

First of all, look at the width of the long red film on the edge of the film. Different models have different widths of red film. For example, a roller with a M-600 circumference of 589 mm in Heidelberg requires a red film width of 23 mm, and M-600 weeks. The requirement for a 578 mm long roller is 23.1mm. The larger the difference from the actual required width is, the larger the scanning result will be affected. Therefore, the actual operation must be combined with the model used, and the appropriate width should be printed through the red film. The field block.

Secondly, check whether the smoothness of the plates used is satisfactory. Sometimes the plates have dents, the surface is uneven, and the scanning results are also affected. The flatness of general domestic printing plates is slightly inferior to the imported foreign versions. Of course, the effect of plate irregularity can be reduced by adjusting the suction amount of the plate scanner. Generally, when the imported media is scanned, the inhalation volume level is selected to be one level. When scanning domestically produced media, the level of inhalation of the second or third stage can be selected. It can be used flexibly according to the surface smoothness of the printing plate, since the inspiratory volume is increased. The printing plate will be more evenly adsorbed on the scanning panel, which is conducive to correctly reflect the ink demand of the graphic part on the printing plate. However, blindly increasing the amount of inhaled air may attract a large amount of dust. Over time, it will block the suction hole and affect the scanning quality.

In short, prepress production should gradually realize that only prepress production can be used to adapt to commercial rotary printing, and commercial rotation printing cannot be used to adapt to prepress production. The pre-press production of commercial rotation printing is complicated and esoteric, and it is necessary to constantly explore and summarize the actual work in order to continuously improve the production level.

Second, the selection of raw and auxiliary materials

Paper

1 There are tension rollers in the front and rear of the commercial web. The paper is transported between the printing units under tension. With the viscous resistance of the ink, the mechanical properties of the paper are long and break. Degrees, tear strength, etc. have higher requirements. The better the mechanical properties of the paper, the less likely it is to break the paper, saving a lot of unnecessary waste.

2 Nowadays, the commodity news of some hypermarkets and the real estate advertisements of advertising companies all require vivid colors and high saturation. Correspondingly, the paper should have excellent printability: water resistance, oil resistance, abrasion resistance, folding resistance, high surface strength, proper pH, and water content. Now more use of light coated paper, the performance of different manufacturers of different products: If the UPM paper imported from Switzerland after printing and drying is more serious surface folds, but the surface is not how to off powder. Some domestic papers are heavily powdered and some have low smoothness.

2. Ink

Commercial rotary presses generally have faster speeds, such as Heidelberg's M-600, which has a speed of 44,000 pairs/hour. This requires excellent ink performance. 1 Wire drawing: The characteristics of drawing, breaking, and springback that the ink layer shows during the splitting process. In the high-speed printing process, the drawing is too long, often forming ink flying phenomenon, at the same time, the springback is weak, the dot is obviously enlarged; the drawing is too short Therefore, the ink transfer is not true, so the required ink drawing size is moderate. 2 heat resistance: the ink on the surface of the printing ink under the high temperature heating resistance to discoloration, if the prints dried by the oven, the ink layer discoloration, graphic blur, indicating that the ink heat resistance is poor. The hue dark ink was found to have better heat resistance in use because the dark hue ink pigment particles are uniform, fine, and high in purity, and the heat resistance depends on the properties of the pigment. 3 ink fineness should be less than 15 μ m, because the rough ink will accelerate the plate wear, and reduce the gloss of the surface of the print, so for the pursuit of high-quality commercial rotation, of course, the smaller the fineness of the ink, the better .

Heidelberg M-600 water tank

3. Fountain solution

The fountain solution for commercial web offset presses is different from press rotation printing, and is more different than offset offset printing. It requires that the fountain solution should be conducive to stable water and ink balance, the amount of water in the ink is small, the concentration of the ink is ensured, emulsification is reduced, and stable printing quality and rapid start-up of the machine are ensured even if the machine is operated for a long time. In the continuous water delivery system, the import fountain solution additive concentration ratio of 2% to 3%, IPA (isopropyl alcohol) ratio of 6% to 8%, the hardness of the solvent water used is 4 ° ~ 25 ° DH, PH value is controlled from 4.9 to 5.2 (according to the water hardness can be slightly adjusted), conductivity 800 ~ 1200μs/cm; the fountain solution used at the same time should make the ink roller does not retain calcium deposits, reduce the residual ink on the blanket And paper powder, to be effective in preventing foam and microbes.

When the pH of the fountain solution is too low. The dampening solution will react with the desiccant in the ink. The stronger the acidity of the dampening solution is, the slower the ink will be dried. When the pH value is too high, the IPA value is often too high and the ink film layer will lose its luster. It looks like the surface of the printed product is velvety and boring.

4. Use of blanket

During the printing process, it was found that after the rubber blanket collapsed, it

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