Phenomenon: The color is uneven during printing, and the concentration becomes darker or lighter when the machine is stopped and restarted.

 

Reason:

1. The pressure between the ink rollers is weak

2. Ink roller aging

3. Uneven supply of waterways

4. Ink has poor water resistance and is prone to emulsification, causing water to accumulate on the ink path

5. The adhesive layer on the surface of the rubber blanket is not suitable, and residual ink, spray powder, and paper wool accumulate, resulting in an uneven surface of the rubber blanket

6. Paper has poor moisture absorption, and water in non graphic parts is not absorbed when entering the next printing color group, resulting in poor ink application and unstable concentration

Phenomenon: The dots on the original sample and printed version cannot be accurately displayed on the printed sample, resulting in dot enlargement, dot undersizing, and dot blurring.

 

Reason:

1. Improper pressure setting between rollers, plates, and rubber blankets.

2. The ink is too soft and lacks sufficient viscoelasticity

3. Insufficient ink concentration and excessive ink application

4. Ink is prone to emulsification, and after emulsification, the ink tends to be soft and has insufficient viscoelasticity

5. The ink load in the ink roller is too large, with too much water and ink

6. Rubber blanket and roller are too soft

7. Excessive imprinting force

8. Insufficient sensitivity of the template and unclear publication

Phenomenon: Patterns that should not appear appear lightly on the ground or in shaded areas, such as previously printed patterns, inconsistent printing direction and density, etc

 

Reason:

1. The ink layer is too thin

2. Ink transparency is too high

3. The viscosity of the post printing ink is too high, causing the post printing pattern to overlap with the pre printing pattern. The pre printing pattern is then returned to the ink roller and rotated once, resulting in the pre printing pattern being printed on top

4. The ink on the rubber blanket is not cleaned thoroughly, and there are residues in the pre printed pattern.

5. The layout design is unreasonable, and there is a significant difference in ink consumption between the actual patterns in the left and right directions. The cross layout of large and shallow tones in the left and right directions results in significant density differences, causing image ghosting

Phenomenon: In the solid pattern printed on the reverse side, there is an area where the gloss is significantly higher than that of other graphics and text, located opposite to the solid pattern printed on the front side.

 

Reason:

1. Large area, high ink volume on-site printing after surface printing

2. When printing on both sides, the oil absorption of the paper is overloaded

3. The amount of ink used for on-site printing on the reverse side is too large

4. After the front printing is completed, the ink should be printed immediately before it dries

5. The sample stack is tightly packed, and oxidation drying produces small molecule gas substances that cannot be released and accumulate in the middle of the sample.

Phenomenon: After printing, there is a color change or gradual fading of the printed material during storage.

 

Reason:

1. The connecting material components in the ink gradually oxidize and turn yellow, especially the varnish.

2. Poor UV resistance of ink

3. The acidity and alkalinity of paper do not match the acidity and alkalinity of ink

4. Excessive IPA addition during printing can cause some pigments to be intolerant to alcohol, resulting in color bleeding when printing dries.

5. Water based varnish and film coating. The alkali resistance and solvent resistance of pigments are poor.

Phenomenon: Ink flies out of the ink roller in the form of atomized particles into the air, which is called flying ink; Flying in the form of large ink droplets near the ink roller is called ink slinging.

 

Reason:

1. Insufficient ink viscoelasticity

2. Low ink concentration, large ink volume

3. Excessive ink emulsification

4. Improper setting of printing pressure

5. The surface of the ink roller is damaged, resulting in poor ink transfer

6. Printing speed too high

7. The printing environment temperature and printing machinery temperature are too high, resulting in ink being too thin.

8. The printing layout is too narrow, and the ink on both ends of the ink roller is emulsified and accumulated for a long time, which fails to transfer and update, and is prone to ink splashing.

9. Static electricity generated during printing

Phenomenon: The ink on the printing surface of the previous sample sticks to the stacking surface of the next sample, causing the graphics and text to become dirty. After being stacked high, the paper sticks together.

 

Reason:

1. Ink penetration and drying are too slow

2. Low ink concentration and large ink volume

3. Excessive ink emulsification leads to slow ink penetration and drying

4. Ink oxidation and slow drying of conjunctiva

5. In low humidity environments, thin paper printing generates static electricity, leading to paper adhesion.

6. Insufficient powder spraying or small particle size

7. The paper is heavy and stacked too high

Phenomenon: A faint color appears on the entire or part of the layout, and after confirming that the printing plate is not damaged, it will immediately reappear after wiping the layout clean.

 

Reason:

1. The ink body is too soft, and when the printing temperature is too high, it is easy to emulsify

2. Excessive addition of ink conditioner and viscosity reducer results in ink being too thin.

3. Pigments have strong hydrophilicity, and water-soluble pigments and dyes are used for offset printing.

4. Ink has poor water resistance, and during emulsification, the connecting material and pigment are easily separated, causing the pigment to enter the aqueous phase.

5. Excessive pressure between the ink collecting roller and the ink distributing roller causes separation of ink and water, resulting in floating dirt.

6. The surface of the ink roller has hardened, and the scraping effect of ink scattered in non graphic parts is not good.

7. The impact force of the water roller on the layout is too strong, and due to the existence of bite gaps, it causes jumping and the bite area is prone to getting dirty. Increasing the water volume may improve, but it may cause floating dirt.

8. Ink on water roller

9. Excessive water lifting of the dampening solution and excessive emulsification of the ink

10. The pH setting of the dampening solution may result in poor acid and alkali resistance of some pigments, making them easily dissolved by the dampening solution.

11. Surfactants and salts in paper dissolve into the dampening solution, disrupting the hydrophilicity of CTP plates.

Phenomenon: Ink is applied to non graphic parts of the printed version.

 

Reason:

1. The surface tension of the dampening solution is too low, and there is insufficient water on non graphic parts

2. Crystallization by water roller, ink coating by water roller, insufficient water coating

3. Excessive printing pressure

4. The greasy nature of the ink is too high, spreading to non graphic areas

5. The ink body is too soft and prone to emulsification

6. The pH of the dampening solution is not suitable, and the conductivity is too high

7. The temperature of the ink roller is too high, causing the ink to become thin and prone to emulsification

8. The CTP version has insufficient exposure, and the non graphic parts have strong oil affinity. The sand particles in the version are small or shallow, and the water retention is poor.

9. Surfactants and salts in paper dissolve into the dampening solution, causing rusting.

Phenomenon: During the printing process, the preceding ink and paper fibers on the print sample are pulled back by the subsequent rubber blanket, accumulating on the rubber blanket and CTP plate, and entering the ink path.

 

Reason

1. Excessive water content on the paper, high ink emulsification, significant decrease in viscosity when ink is transferred to the paper, and poor adhesion to the paper surface.

2. There is a lot of dust and paper powder on the surface of the paper.

3. Loose paper and low adhesive strength.

4. Printing speed too fast, ink viscosity increases too much

4. Excessive imprinting force makes it difficult to peel off the paper ink rubber blanket.

5. Ink viscosity is too high

6. Poor stability on the ink machine, fast increase in viscosity

7. The printing temperature is too low, the ink temperature on the ink roller is low, and the ink viscosity is high.

8. Low paper temperature in winter causes paper brittleness and low surface strength.

9. Improper selection of rubber blanket makes it difficult to peel off non graphic parts.

10. Improper selection of cleaning agents. The plasticizer in the rubber blanket is dissolved and carried away by the cleaning agent, and the solvent in the ink is absorbed by the rubber blanket during printing, resulting in significant thickening.

Phenomenon: Easy to scratch during printing, and prone to scratching during sample storage and transportation.

 

Reason:

1. When high gloss is required for printing samples, the amount of wax added to the ink is low and the wear resistance is insufficient.

2. Paper absorbs ink quickly, causing ink powdering

3. Poor drying caused by ink and paper

4. The surface of the paper is uneven

5. The printing paper path is not cleaned thoroughly, resulting in ink blocks, paper hairs, and powder lumps protruding, causing scratches.

6. Flip printing before ink penetration is complete

7. The layout design is unreasonable. The shallow web design has a large format, thin and discontinuous ink film, and low film strength, especially for blue ink.

Phenomenon: After the ink is transferred to the paper and dried, the pigment and substrate are not firmly bonded, and powdery substances are prone to fall off during friction.

 

Reason:

1. The capillary absorption of paper is high, and when ink penetrates, the connecting material is easily sucked into the paper together, resulting in exposed pigments.

2. The penetration speed of ink is too fast

3. High ink concentration and thin ink layer

4. The oxidation drying speed is too slow

5. The paper is too acidic, causing poor drying.

6. The pH of the dampening solution is too low

7. The ink is too soft, and after printing, the body and bones cannot be maintained

8. Excessive water supply of the lubricant, excessive emulsification of the ink, and separation of the binder and pigment.

Reason:

1. Excessive ink emulsification, insufficient water absorption of paper, and acidic salts in the dampening solution affect drying.

2. Printing ink volume is too high

3. The moisture content of the paper is too high

4. The acidity of the paper is too strong

5. Paper has low or no oil absorption.

6. Inaccurate parameter setting of lubricant solution

7. Insufficient oxygen in the stacking environment

8. The ambient temperature is too low and the relative humidity is too high

9. Excessive addition of ink conditioner, demulsifier, and anti caking agent to the ink

10. After being stored for more than 1 year, the desiccant of black ink is absorbed by carbon black, causing slow drying.

Phenomenon: The ink in the ink hopper is transferred less to the ink hopper roller or detached from the roller, resulting in a lower concentration of the printed sample.