How to correctly use the test strip to control the

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How to correctly use the test strip to control the exposure of PS version (Part 2)

II. Taiyi light source is placed on the right side, but for the laboratory machine industry, the model of plate printer: sby920 light source power gallium iodide lamp 2000W, layout size 1200mm, maximum incidence angle 26 °

Test 3: Based on the level 3 cleanliness in the middle of the layout, the left, right, front, rear and middle of the layout are exposed to a PS version respectively, Exposure time: 70s data as shown in table 4:

Table 4

position left front middle rear right

ladder (level) 2 2.5 3 2.5 2

III. Japan eye source upper printer:

model: p832-g light source power 4000W layout 1200 × 900mm lamp distance 1100mm maximum incidence angle 28 ° exposure unit: 12s

Table 5

position left front middle rear right

ladder (level) 2 + 2.5 + 3 + 2.5 + 2 +

from the above four groups of tests. If the printer is placed on the light source, the light on the layout should be more uniform than that under the light source. Of course, generally speaking, the light distance on the light source is larger

the exposure between the middle and the two edges of the cabinet printer under the big Japanese eye source is twice as large (or the printer we tried may not work properly)

no matter what the structure of the plate printer, the illumination difference of each part of the plate is obvious. Therefore, when making plates, you must pay attention to the position of the test strip, which is the eternal law, and find out the corresponding relationship to correctly control the exposure

for the PS version, the higher the sensitivity, the smaller the absolute value of the exposure wide window capacity, and the greater the difference in the exposure of various parts of the PS version when printing. When printing, the exposure should be determined in front, back, left, right and middle. 3. During operation, do not stretch your hand or stick into the mixing bag or clear the mortar at the mouth of the bag. The edge should not be clean at Level 3, so the middle part should be overexposed; It is also not allowed to take the middle level 3 clean as the standard, so the exposure of the edge part is obviously insufficient

the exposure of PS plate printing should also take into account the relationship between the tone reproducibility of official prints and the tone reproducibility of samples. Theoretically, the size of the dot on the sample is basically the same as that of the original, and the tone reproducibility of the official print should also be consistent with that of the sample. However, the official printing offset press is a rotary machine for round pressing, and the proofing machine is a platform machine for round pressing. The printing speed, printing pressure and ink transmission methods of the two machines are different. To reduce the dot expansion of the official print to the level of the sample, it is generally to increase the exposure to make the dot slightly smaller, so that the official print can be basically consistent with the sample. The standard of dot enlargement value is related to the printing machine and paper used for printing. The dot gain value of coated paper is obviously smaller than that of offset paper. The standards and benchmarks of point spread values in various countries are also different. China's point spread values are set at 50% points. Current expanded value of point: fine products ≤ 12%, general products ≤ 18%

of course, the illumination uniformity of different printing machines is different. Users had better experiment with the best exposure conditions by themselves

in general, pay attention to the position of the test strip during plate making, find out the corresponding relationship, and correctly control the exposure. For plates, PS plates with high sensitivity and low exposure tolerance should pay special attention to this problem when making plates

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