Technical problems arising from offset printing in production

The technical problems arising from the production and use of offset printing mainly include the following three points:

1. Offset printing plate to master the exposure time, development time

Offset printing control One of the ways to reduce the dot enlargement and shrinkage is to control the exposure time, development time, developer humidity and concentration ratio. The four-color film from the color separation passes through the process of printing, shifting the image and text points to the printing plate, requiring that the network points be expanded and lost as little as possible, 3% to 5% of the network points should not be lost, and 5% of the network points should not be expanded. 95 % ~ 98% of the outlets are not affixed, the outlets are firm, the dots are neatly arranged, the outlets have no white dots, and the burr edges are rich, complete, and clear.

This requires accurate preparation of good PS version of the developer, according to the formulation of the developer specifications, do not look more, less, exposure time with grayscale ruler, print version of the signal to data control, after the printing plate out of the sun 5 to 10 times the magnifier check is lost at the step scale and signal bar level, and the paste version and dot gain are enlarged.

2. Reasonably choose the offset lining material to adjust the printing pressure

Offset has three kinds of hard, neutral and soft linings. What kind of lining is best? It can be said that each has its own characteristics. Offset printing is a kind of indirect printing method. It requires the middle of the rubber roller to transfer the printing plate image net point to the surface of the paper. The eraser and its lining material is the middle of the graphic transfer in the offset printing. Media, no lining, no printing pressure, no indirect printing, no offset printing.

By adjusting the thickness of the lining of the offset printing press, a reasonable and optimal printing pressure can be obtained, and the uniformity of the ink shades of the printed product and the clarity of the dots can be enhanced. In addition, the reasonable lining can be used to reduce dot gain and increase the number of dots. The printing plate's resistance to printing force is very helpful.

The printing pressure is obtained by the two methods of lining thickness and roller center distance adjustment. Generally speaking, whether the printing pressure is appropriate or not is often expressed by the quality of the printed matter.

The pressure should be based on the premise that the prints have strong dots, clear graphics, vivid colors, and shades of light. The smaller the application, the better, the control of the dot expansion, and the adjustment of the accurate printing pressure are critical. The printing pressure is high, and the dots are expand.

Accurately calculate and use the micrometer to measure the thickness of the blanket cylinder lining, adjust the center distance between the two cylinders, and within the allowable range of the dot expansion, the footprint is sufficiently strong and evenly use the minimum printing pressure.

3. Offset printing control ink balance, reduce network expansion

Offset control to control the ink balance, in order to improve the quality of printed products, advocated in the premise of not dirty version, paste version, use as much as possible the layout of the water, thus compared to the emulsification of ink and paper stretching deformation, ink balance is also a measure of offset The standard of operator's technology is only to achieve the balance of water and ink shrinkage, small, high overprint accuracy, color, color, hue can be consistent with the proof of a group of printed ink color depth, printed dot network particles are strong, flat The cable is flat and at the same time it also reduces the expansion of outlets.

Avoid large ink and large ink layers during offset printing. Extend the dot spreading of the ink layer too thickly outward. Control 3% to 5% bright tone in the area. Small dots are not lost. 5% of the intermediate dots do not expand. Do not expand or contract. 95% to 97% of large outlets do not overlap, and the control standard for the amount of ink is as follows: a well-defined and well-printed dot and ink color hue are used with as little ink as possible.