Offset Key: Sunrays PS version drying process control (2)

Third, the drying frame glass

The shelf plate glass is clean. Otherwise, dust on the glass can easily make the PS plate dirty. Due to the fact that our current working conditions are difficult to achieve absolute cleanliness of the printing workshop, we must wipe the printing plate glass with alcohol prior to printing, and we must wipe both the front and the back to eliminate the glass. Dirty spots are generated by dust.

Wiping the glass should avoid scratching the glass with hard objects on the hands, and ensure that the cloth or sponge that wipes the glass does not have sand particles, so as not to damage the glass.

When the glass plate of the printing plate is scratched too much and too deep, the glass must be replaced. Otherwise, when drying the flat screen, dirt spots will be generated, resulting in a large number of waste plates.

Fourth, good pumping
Insufficient evacuation vacuum level can cause poor adhesion of the original film and the photosensitive layer of the plate, resulting in voids and severe light penetration, thus changing the size of the dots or even losing them. Therefore, we need to find a suitable pumping time, so that the PS version and the original film can be closely integrated in order to facilitate the correct exposure.

When the air pumping blanket is used for a long time, there will be aging, and there will be a small amount of air leakage in some edge areas. The PS version and the film will not stick tightly, and the printed text will be too weak. At this time, the manufacturers should be contacted. Replace the blanket.

When you inhale, if you can't walk from the middle to the surroundings, you will have local bubbles, and the PS plate will be partially blurred. At this time, check the bottom plate.

V. Accurate exposure time
We only have a good PS version, good exposure conditions are not enough, but also have sufficient and not excessive exposure time to produce a good PS version.

As the use of printing plate will increase part of the production cost, the confirmation of the exposure time of many printing factories is often judged by experience, resulting in extremely unstable printing quality.

If we want to obtain a stable print quality, we must use the print control signal bar (such as: UGRA1982 print control bar), through the print test, to find out the standard exposure time and development time.

UGRA1982 measurement and control bar consists of five parts:

A, highlights and dark tone control area, usually in the sun print pattern: to ensure that 98% outlets do not paste, 2% outlets to be preserved: In the printing on the printing machine: to ensure that 97% outlets do not paste, 3% outlets to Reservations.

B. Test ghost area.

C. The dot area used to measure dot gain and print contrast.

D. Twelve Yin Yang patterns with a diameter of 4.5 mm. The width of the line is between 4 μm and 70 μm. This section can be used to determine the correct exposure time and resolution of the PS plate.

E. Gray scale used to test whether the development is normal.

(a), test steps:

Exposure: The UGRA control strip is placed on a PS plate to be tested. The PS plate is exposed using a T, 1.4T, 1.42T, 1.43T, 1.44T, 1.45T,... 1.4 times for the previous stage, such as: the first exposure is 10 exposure units, the second is 1.4 x 10 exposure units, until the last exposure exceeds the normal exposure.

Development: Use the developer stock matched with the PS plate and dilute it according to the developer's standard ratio. Put the exposed PS plate flat on the developer tank. Use the manual development method. Take about 0.5-1 minute and then take it out and wash it. Plate platform flush with water.

The method of manual development is to avoid inaccurate development time and unfavorable developer concentration.
Exposure time T 1.4T 1.42T 1.43T 1.44T 1.45T
Reproducible female line width 20μ 8μ 6μ 6μ 4μ 4μ
The smallest reproducible width of the male line 4μ 4μ 6μ 10μ 15μ 20μ


(B) The resolution of the PS version resolution
The most important factor affecting the virtual reality of printing plates is the resolution of printing plates. The higher the resolution of printing plates, the better the performance of small outlets and the more real the outlets. At the same time, if you want to determine the exact exposure time, you must first confirm the PS version of the resolution.

Observe the reproduction of the yin and yang lines of the yin and yang loop area of ​​the UGRA control strip using a 10x magnifier (at least 50% can be clearly reproduced).

According to the regulations of the UGRA1982 measurement and control strip, at a certain exposure time, the same level of the Yin and Yang lines in the yin and yang circle area can be clearly observed at the same time. This level is the resolution of the printing plate, as shown in the above table Edition resolution is 6μm.

(to be continued)

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