Summary of offset printing technology experience: sheetfed offset printing precautions

Summary of offset printing technology experience: sheetfed offset printing precautions

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Ink performance

Concentration: The ink with a large concentration is used less in the printing ink, and the ink color is better; the ink with a small concentration is used more in the printing, and the ink color is lighter;

Fineness: the size of the ink particles, the ink fineness, the ink concentration is large, the print dot is clear, full and powerful; the ink fineness is low, the dots of the printed matter are easy to hair, and the printing plate has a low printing durability;

Viscosity, viscosity, easy to cause uneven ink transfer, dot pulling and stencil; the viscosity is small, easy to cause ink emulsification and plate surface floating phenomenon;

Mobility: The fluidity is large, the image is unclear, the ink color is not full; the fluidity is small, so the ink transmission is not smooth and uneven, and it is easy to cause the front and the back to be shallow or shallow and deep after the same printing surface. The phenomenon;

Light resistance: ink with good light resistance, printed products with beautiful color, full and solid image, full of three-dimensional sense, and can be stored for a long time.

Dampening solution

The pH value of the fountain solution is generally between 3.8 and 4.6. In the actual production, it should be adjusted according to the specific conditions of the printing conditions. If the dampening solution is too acidic, the sand-eye and the lipophilic part of the blank part of the layout will be corroded. The sex will increase, which will easily cause the pattern phenomenon, which will reduce the printing durability of the printing plate; at the same time, the ink will be easily emulsified, the ink roller will be deinked, and the printed matter will be dull.

If the acidity of the dampening solution is too weak, the hydrophilic and oil-repellent properties of the blank part of the printing plate will be weakened, the layout will be dirty and the paste will be caused by the enlargement of the printed dots (if the dampening solution is acidic and too acidic when printing on UV ink, The layout is easy to get dirty.)

Color order

The color sequence refers to the sequential printing sequence of each color printing plate in multi-color printing. Different color sequences will produce various printing effects, and it is important to arrange the color sequence reasonably. But the color order is not absolute, the color order is generally arranged as:

Monochrome machine: yellow → magenta → green → black two-color machine: black → yellow → magenta → green (print landscape) or blue → red (printed characters);

Four-color machine: black → green → magenta → yellow

When there are gold, silver, and full-page printing, it is generally necessary to first gold, silver, and full version of the field, and then set the four-color ink after the ink is dry.

Batch printing

Check if the specifications of the four-color film are consistent;

Check the proof and check whether the graphic is complete;

Stabilize moisture and ink volume to achieve ink and water balance to ensure the same ink color of the same batch of prints;

Try to clean the blanket after a small amount of downtime or downtime (you can put some overprint paper).