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Common Quality Abnormalities in Gravure Printing and Solutions (6-10)
Time: 2018-10-24 Source: Packaging Frontier Reading: 5209 times
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Wenzhou Junchuan Machinery Equipment Co., Ltd.

Six, indentation

Intermittent irregular boundary line marks appear in a certain color in the text, with different shapes, varying thicknesses, different lengths, and uneven shades. Generally easy to appear in a large area of the ink volume of the unit color.

Abnormal:

Too much printing pressure

2. Ink viscosity is low

3. The scraper is too flat (the scraper angle is too small)

4. The roundness of the impression cylinder is poor, and the thickness is uneven.

5. Ink accumulates on one or both sides of the impression cylinder

6. Elastic edge of original film

7. Printing plate beating

8. Imprint cylinder bounces

9. Inconsistent air pressure settings on both ends of the impression cylinder

10. The cylinders at both ends of the impression cylinder are malfunctioning, resulting in inconsistent air pressure

11. The electrostatic ink absorption voltage is too high

solutions:

Appropriately reduce printing pressure

2. Properly increase ink viscosity

3. Properly adjust the scraper angle

4. Replace the impression cylinder with better roundness

5. Use a cloth dipped in solvent to remove the accumulated ink on the impression cylinder.

6. Replace the original film

7. Shut down and reinstall

8. Stop and replace the impression cylinder or replace the impression cylinder bearing

9. Adjust the air pressure at both ends of the impression cylinder to be consistent

10. Ask the maintenance department to repair the cylinder of the impression cylinder

11. Reduce the voltage value appropriately


Seven, dry

The printing ink on the printing plate dries prematurely (drying too fast), resulting in uneven dots in the parts of the printing material that should have a uniform effect. It usually appears at the beginning of the printed matter and extends backward. Observe its shape, like a flame.

Abnormal:

Printing speed is too fast

2. Improper ink viscosity control (higher)

3. The scraper angle is too large (the scraping dot is too far away from the printing dot)

4. The printing plate dot is shallow

5. The wind leaked from the drying oven is blown onto the printing plate

6. There is wind current near the printing unit (such as: equipment exhaust air, ink pump air leakage, air conditioning air, etc.)

solutions:

Reduce printing speed

2. Reduce ink viscosity or add slow-drying solvent

3. Adjust the scraper angle to reduce the distance between the scraping point and the printing point

4. Remake

5. Prevent air leakage or backfill in the drying oven

6. Prevent air flow from equipment exhaust air, ink pump air leakage, air-conditioning air from blowing to the printing plate

Eight, overflow

The overflow of ink along the back side of the pattern makes the horizontal lines thicker, the contour of the pattern blurred, or the color appears in the place where there is no color, which looks like an irregular mountain peak or triangle. Looking at the overflow with a magnifying glass, the ink piled up without dots.

Abnormal:

Printing plate dots are too deep

2. Ink viscosity is too low

3. Printing speed is too slow

4. Printing pressure is too low

5. The scraper angle is too small

6. Scraper port is slightly damaged

7. The printing plate is beating

solutions:

1. Remake the plate and deepen the outlets

2. Properly increase viscosity

3. Speed up printing

4. Properly increase the scraper pressure

5. The scraper moves backwards to increase the scraper angle

6. Replace the scraper

7. Reinstall the plate so that it does not jump or reduce printing speed

[Special Reminder]: It needs to be distinguished from "tailing", the phenomenon is similar, and the meaning and cause are completely different. Smearing is a line-shaped anomaly, and overflow is a block-shaped or flaky anomaly.


Nine, plug version

The foreign matter (such as curing agent or dried ink) of the printing plate's dots is clogged. The ink transfer within the dots is poor during printing, which causes unevenness, unevenness, or incompleteness of the printed matter screen that should be uniform and clear.

Abnormal:

1. The ink on the surface of the printing plate is dry and hardened after being stopped for a long time

2. Impurities and foreign matters in the printing ink (paper powder, ink skin, ink sticks) are involved, and the printing plate dots are blocked (most commonly: at the end of the previous batch, the printing plate is not rinsed clean, resulting in curing agent or drying out Residual ink will plug the printing plate dots)

3. Insufficient printing dots

4. Solvent use error

5. Ink usage error

6. There is a large air volume around the printing press (for example, the exhaust door cover of a Rodmike printing press is accidentally opened, causing the ink in the dots to dry out in advance

7. Limited by the printing process (some colors of some special orders require high viscosity due to the characteristics of the ink and printing effect, and it is easy to jam the plate when printing)

solutions:

1. Use a nano sponge to wipe the plate after soaking it in the solvent (Note: It is not recommended to use a cloth to dip the cleaning powder to clean the printing plate in the normal production process, which will cause the sheet to be out of ink and cause customer complaints. Wipe the plate with decontamination powder, be sure to clamp the strip in time and remove the inspection product)

2. Shut down with a steel brush dipped in the cleaning solution to remove the ink residue or foreign matter in the printing plate more effectively.

3. Remastering and deepening outlets

4. Stop cleaning the ink tank and re-dispense the ink

5. Stop the machine to clean the ink tank and replace the ink. If necessary, clean the printing plate dots.

6. Close the cover or cover it with a film to reduce external airflow

7. Use the ink guide roller to apply ink to the printing plate (because the ink guide roller is in constant contact with the printing plate halftone dots, there is a certain friction force, which plays the effect of erasing the plate at any time. If the ink guide roller is a driving roller, it is better if it is driven Rolls are also available)

Ten, lack of ink

There are three cases where there is no ink transfer on the printed graphics:

1. Large pieces of ink that are not fixed horizontally and vertically and have different shapes-caused by insufficient ink quantity;

2. Insufficient ink in a small area with a fixed horizontal position, a fixed vertical position, and a similar shape-caused by an abnormality of the impression cylinder or an abnormality of the scraper frame;

3. Insufficient ink in a small area with the same horizontal and vertical positions and the same shape-caused by abnormal printing;

Another very rare situation is that the equipment has a small amount of water and oil leakage and accidentally drips onto the printing plate, resulting in the ink not immersed in the printing plate dots. The bad phenomenon is that the horizontal position is fixed, the vertical position is also fixed, and the shape is similar. But the scope will become smaller and smaller.

Abnormal:

Insufficient ink in the ink tank

①. The amount of ink used is large, and the amount of ink discharged from the ink pump port is too small

②. Too little ink in the ink tank causes the ink pump to fail to get ink

③. During the production process, the ink tank drops for some reason, resulting in insufficient ink level

2. Improper ink tank height

①. When it is too low, the ink in the ink tank is not enough to immerse all the graphics on the printing plate

②. When it is too high, the ink tank, or the sediment in the ink tank, scratches the printing plate and the text, and wipes off the ink on some of the graphic

3. The paper behind the scraper frame is too long, curled, and touches the graphic on the printing plate.

4. Foreign matter (such as flying insects, dry ink sticks) adhere to the impression cylinder

5. The impression cylinder has slight depressions and pits

6. Poor roundness of impression cylinder

7. Defects in the halftone engraving of the printing plate (the halftone engraving is missing)

8. There are abnormal protrusions on the surface of the printing plate (the ink in part of the protruding dots is scraped off by the scraper, which will also cause the lack of ink)

9. There are foreign water drops or oil drops on the printing plate (the device has a small amount of water and oil leakage, accidentally dripped on the printing plate)

solutions:

Ensure the amount of ink in the ink tank

①. Increase the working capacity of the ink pump and increase the ink output

②.During regular inspections, add ink in time to find out

2. Appropriately adjust the height of the ink tank (It is advisable to immerse the printing plate in the ink tank by about 1 ~ 2cm)

3. Properly shorten the height of the back paper to prevent it from curling or reduce the height of the ink tank.

4. Remove foreign matter from the impression cylinder

5. Appropriately increase the printing pressure (so that the dent of the impression cylinder can be evenly pressed to the printing plate dot)

6. Replace the impression cylinder with better roundness

7. Remake

8. Reduce the pressure of the doctor blade and increase the pressure of the impression cylinder (so that the dots on the raised portion of the printing plate can keep the ink transfer)

9. Prevent foreign water and oil droplets from splashing on the printing plate


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