How to correctly use the test strip to control the exposure of the PS plate (bottom)

Model: SBY920 Light source power iodine lamp 2000W Layout size 1200mm Maximum incident angle 26°

Test 3: Based on the clean 3 position in the middle of the layout, the left, right, front, back, and middle plus test strips of the layout are each exposed to a PS plate. Exposure time: 70S data is shown in Table 4:

Table 4

Model: P832-G Light source power 4000W Layout 1200×900mm Light distance 1100mm Maximum incident angle 28° Exposure unit: 12S

table 5

From the above four groups of tests. The light source is set on the printing machine, and the light on the screen is evener than the light source. Of course, in general, the light source on the light source is large.

The exposure between the middle and the two edges of the cabinet printing machine under the Da Nippon mesh light source is twice as big (or the printer may not work properly if we try this).

Regardless of the structure of the stencil, the difference in illuminance at each part of the plate is obvious. Therefore, we must pay attention to the location of the test strips during the plate making process, and find out the correspondences among them to properly control the exposure.

For the PS version, the higher the sensitivity, the smaller the absolute value of the exposure window width, and the greater the difference in the amount of exposure of each portion of the PS plate at the time of printing. The determination of the amount of exposure during the printing should be taken into account before, after, left, right, and in the middle of the line. It should not be based on the cleanliness of the edge 3, so that the middle part should be overexposed; nor can the middle 3 levels be clean, so Exposure to the edge is clearly insufficient.

The exposure of the PS version should also take into consideration the reproducibility of the formal print and the reproducibility of the proofs. In theory, the size of the sample Internet sites is basically the same as that of the original, and the reproducibility of the formal prints should also be consistent with the reproducibility of the proofs. But the official printing offset press is a round press rotary press, and the proof press is a round flat press. The printing speed, printing pressure, and ink transfer method are different for each other. The level of small proofs is generally used to increase the exposure, so that the network points are slightly reduced, so that the printed official print can be basically consistent with the proofs. The criteria for dot gain values ​​relate to printing presses and paper. The dot enlargement value of coated paper is obviously smaller than that of offset paper. The expanded value standards of various countries are also different, and the benchmarks are not the same. Our country's network expansion value is set on the basis of 50% outlets. Network expansion values: Fine products ≤12%, general products ≤18%.

Of course, the illumination uniformity of the different printing machines is not the same, and it is best for the user to test an optimal exposure condition himself.

In general, when making a plate, you should pay attention to the position of the test strip, explore the correspondence, and properly control the exposure. For plates, the PS plate with higher sensitivity and smaller exposure latitude should pay special attention to this issue when making plates.