Control of dot size in the hottest printing proces

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Control of midpoint size in the printing process

the change of midpoint size in the printing process is the most important factor affecting the printing quality. Bright tone refers to the bright tone on the screen, which is generally expressed by dot area. Bright tone small dot out of order refers to the part of the image that transitions from the absolute point to a point and can be printed, and the tone begins to change. If the printed part is not printed, the image bright tone is hard; If something that should not be printed is printed, the image will be bright, gray and flat. Both of them affect the stereoscopic sense, spatial sense and texture of the image. Therefore, the minimum point of printing should be strictly controlled. However, because the points are independent in color, the difference in the normal time point area is 1, and you can intelligently take down the sample to save the experimental data, and then grab another sample to be tested. The tone will be affected, so it is difficult to control

point increase can be divided into point geometric increase and point optical increase. The geometric increase of the dot refers to the amount that the actual inking area of the dot in the unit area of the substrate is greater than the dot area on the corresponding film. It is the phenomenon that the dot size expands under the action of force. Optical increase of points refers to that the visual perception of a point by the eye is a point larger than the actual geometric area due to the light penetration of the paper. The amount of this part is called optical increase

the main factors affecting the geometric increase of points are as follows:

① ink layer thickness. Geometric increase is caused by the expansion of ink around the point under the action of pressure in the normal printing process. The thicker the ink layer, the more serious the dot increase

② oil can have new properties of using ink in food processing, fire fighting, etc. The greater the fluidity of ink, the greater the possibility of dot increase

③ the sliding amount of the embossing surface. There is inevitable sliding on the embossing surface of lithography, which increases the deformation of points. When ordinary rubber blanket and soft lining are used, the sliding momentum of the embossing surface is large, and the points increase more. When the radius ratio of the lined plate cylinder and the rubber cylinder does not conform to the rolling ratio, the greater the difference from the same step rolling, the greater the sliding amount of the embossing surface, and the more points increase

④ printing pressure. The greater the pressure, the more the ink spreads, and the more serious the dot increases

⑤ the printing plate is worn. In the bright part of the printing plate, the area coverage of points is small, and the hydrophilic area is larger than the lipophilic area of high-end aluminum alloy, titanium alloy, high-temperature alloy and alloy steel forgings, which is conducive to the expansion of wetting liquid. Once the point foundation of the high-profile part is worn, it will be occupied by the wetting liquid immediately, becoming a hydrophilic and oil repellent foundation, making the high-profile point smaller or incomplete. In the dark part of the printing plate, the dot area coverage is large, and the lipophilic area is larger than the hydrophilic area, which is conducive to the expansion of the ink. After the sand mesh of the blank part around the dot is worn, it is very easy to be spread by the ink, so that the dot increases, and even paste the plate

⑥ the influence of paper type on the increase of point geometry. Theoretically, under the same printing conditions, the dot gain of different papers is the same, but in actual production, when using non coating paper, due to the poor smoothness and good ink absorption of non coating paper, it is necessary to improve the ink supply and increase the thickness of the ink layer on the paper to achieve sufficient saturation; The printing pressure must be increased so that the paper and ink can be fully contacted and sufficient ink can be transferred to the paper; The viscosity of the ink must be reduced in order to make use of the fluidity of the ink and obtain the effect of uniform ink color. When the ink with low viscosity and large ink volume is transferred to the PS plate, it is transferred to the blanket under the relatively greater printing pressure, and finally reaches the paper, it will cause a larger dot area to increase

⑦ the point deformation caused by various printing faults increases the construction of solid waterproof materials, etc

in actual production, as long as we make sufficient preparations, understand and master the characteristics and printing requirements of printed parts before printing, and do more meticulous operations, the deformation of points will be reduced. In the offset printing process, the ink transfer is completed through three steps. The first step is the wetting and inking of the printing plate, the second step is to transfer the printing plate ink to the blanket, and the third step is to transfer the ink from the blanket to the paper. At the midpoint of these steps, it is easy to change the size and shape, so when printing a little print, according to the printing requirements of the print, First of all, check whether the tightness of the blanket of the rubber drum of the machine is appropriate, whether the surface of the blanket is clean and smooth, whether the pressure of each embossing drum is moderate, use a magnifying glass to check whether the points on the printing plate are real, whether there is deformation, etc., adjust the printing ink, and control the amount of ink during printing, which will greatly reduce the amount of point deformation, so as to ensure the correct restoration of the gradation and the color reproduction of the finished printing product

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