Four color printing process on the hottest monochr

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Four color printing process on monochrome printing machine

for obvious reasons of cost, quality and production efficiency, most four-color printing is completed at one time on multi-color printing machine. It is a challenge to complete four-color printing on a monochrome printing machine. However, printing four-color products on a monochrome printing machine also has certain advantages. For example, because its printing method is dry overprint, and the double focus expansion caused by blanket and transfer cylinder is less, better ink overprint effect is an obvious advantage. However, due to some obvious defects, the method of printing four-color prints with monochrome machine has not been recognized by people. The main disadvantages are as follows: when the relative humidity in the air changes, the size of the paper lacks stability, which brings great obstacles to completing registration many times. After many times of transmission, more dusting will accumulate and pollute the blanket. Finally, the final result of composite color cannot be seen between two printing. Note: the ink overprint mentioned here (wet overprint or dry overprint) is the ability of one ink to transfer and adhere to another ink. Trapping refers to the amount of overlap between two adjacent colors, so that there will be no white leakage on the paper when it cannot be completely set. Ink sequence in four-color printing on monochrome or two-color printing machine what kind of ink sequence is used in four-color printing on monochrome or two-color printing machine? For four-color products, there are 24 different possible combinations when determining the order of printing colors. Printers need to choose the best one from these choices. If four-color printing is carried out on a four-color printing machine, it is the most common "and the recommended order is magenta, cyan, then yellow, and finally black; Or the order of CMYK. This order can reduce the unnecessary color difference in multicolor overprint. Color difference is the amount of unnecessary pollutants obtained from the superimposed second color ink owned by monochrome ink. For example, when 100% yellow blocks and magenta blocks are overprinted, Xi 1. According to the classification method, it can be divided into metal material testing machine, non-metallic material testing machine, dynamic balance testing machine, vibrating table and nondestructive testing machine, etc. it is hoped that the red tone can be obtained, but it does not. The actual result is an orange tone, because magenta inks usually contain about 50% of the mixture crossed with yellow inks. When the butter ink is printed on the magenta ink, the yellow ink will be mixed with the following colors in the wet overprint process, and finally produce a overprint tone, which is slightly yellow than the ideal. Similarly, magenta ink contains 25% of magenta ink. This is why a 100% green and magenta color block will not produce the expected blue tone, but look a little purple. Butter ink is relatively clean and pure. When four-color printing is carried out on a two-color printing machine, the color of the first printing process is very important. They are yellow and black. The contrast of yellow is very small and difficult to see alone. Using a blue filter to observe the yellow color on white paper - for example, Kodak Wratten 47 - can make yellow three look like black. In fact, PMT (photomultiplier tube) drum scanner or CCD (charge coupled device) platform scanner and image densitometer all use the same filter. It is precisely because yellow color is difficult to see that yellow should be controlled by means of reflection densitometer. Black does not affect the hue of a color, it only makes the color darker and dirtier. Adding black to CMY Tri Color printing only increases the density to expand the dynamic range and establish contrast. Black is not only used to achieve gray balance in neutral gray. Gray balance is achieved by adding halftone dots. Magenta and yellow dots are smaller, while green dots are larger. A typical neutral gray balance consists of 65% green dots and 50% magenta and yellow dots. By the way, whether black color is added to any color, the final result is to deepen the color. Conversely, whether white color is added to any color, it will eventually make the color lighter. The hue remains the same. Because the white paper can be displayed and mixed with the color to make the color look lighter. Returning to the problem of printing color sequence, we should prevent any possible back sticking problems. In the first printing process, we should print yellow first, and then black. If there is any back sticky problem caused by the ink film thickness caused by the plate cover or incorrect ink viscosity, yellow will stick to black and not be noticed. It is recommended not to change the color sequence, because this is the overprint of yellow and black, which will cause yellow to become dirty. In the second printing process, the two printing colors are magenta and cyan, which are very important. Magenta and cyan undertake the task of producing sub tones, such as blue sky and water. In the second printing process, cyan is also partly responsible for generating green grass and leaves when mixed with yellow. Magenta is partly responsible for the generation of skin color and foods such as bread and meat when mixed with yellow. When printing four colors on a monochrome printer, it is recommended to print black first. Don't use old information. Some people still decide the order of ink printing based on outdated information. Raw materials such as ink, paper, printing plate, ink roller and fountain solution have been greatly improved, so some operations should be changed with the change and progress of time. For example, yellow ink was not as transparent as current yellow ink. Therefore, yellow ink must be printed first. Now the situation has changed a lot. People usually choose such an order: first, print the color with the largest ink coverage, and then print the color with the smallest ink coverage, so that the ink can overprint better. Ink overprint is a phenomenon greatly affected by various but related factors. Overprint is affected by the absorption or anti absorption of the paper (compared with uncoated and coated), the speed of the printing machine (compared with slow sheet fed printing machine), the residence time or the distance between units, as well as the ink viscosity, the ratio of connecting materials (also known as filler) and the ink film thickness (IFT). Ink pull meter is such a device, which can measure the viscosity of ink. When discussing overprint, these factors must be considered. Generally speaking, monochrome and two-color printing machines have much larger dot expansion size than multi-color printing machines. This is because many sources of dot enlargement are that the shape of the dot is destroyed. This special point gain is called double shadow or double shadow. Ghosting occurs when circular points or other shape points are no longer symmetrical but elongated, just like egg shaped or comet tail. Double shadow occurs when a printed point is slightly inaccurate on the next set of blanket. The next cycle will print a light ghost next to the darker dot. Under the magnifying lens that the central government can increase the special transfer payment for resource exhausted cities in Jixi, it is easiest to see double shadows in the delicate highlight where plastic packaging materials account for more than 30% of the total amount of all kinds of packaging materials. Of course, some color bars have visual indicators, such as the star indicator of GATF or the concentric circle of RIT. All these visual indicators are very sensitive to ghosting and point spread. If you encounter a large number of dot enlargements in multicolor printing, one way to solve it is to drag a printing plate and observe whether the dot enlargements are reduced. If so, the reason for dot enlargements comes from the contact of the blanket that follows. The products printed by the most modern sheet fed printing machine are relatively sharp and tidy, with only 18% of the points enlarged. The earlier the color is printed, the more dot enlarges, because the more times the color passes through the blanket, the larger the double shadow and double shadow. Printing machines without roller pillows are more likely to produce dot enlargements. As we have said before, the disadvantage of four-color printing on a monochrome printing machine is that you can't see the final result that conforms to the color during each printing process. If one of the colors is not printed correctly, the ink density is too black or too bright, or the dot expands too much, there is nothing to do. On multi-color printing machines, the paper handover is very complete and it is very easy to evaluate the color and correct it. Would you consider a way to simulate the final color display between two printing processes? If you buy or use a multi-layer overlay proofing machine, you can superimpose each independent color layer to predict what color will be when printing is completed. This practice is quite good. Because the final color result can only be known after the last printing process is completed, the printer operator must rely more on the instrument with densitometer to evaluate each intermediate color. Some multicolor printer operators are now too lazy to use densitometers because they can see the final composite image. Monochrome printers must use reflection densitometers to monitor and control the printing process as needed. This procedure restricts the work to some extent, and can produce less color difference in the whole production process than visual color detection with eyes. Generally, the color block density specification for sheet fed printing on coated paper is green: 1.30, magenta: 1.40, yellow: 1.00, black: 1.80. This is general data. Each manufacturer needs to regulate them to meet specific conditions. Moreover, the conventional tolerance is not more than 0.05 of the target value

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