Analysis of common failures of offset printing ink (2)

·Circular white spot:

Phenomenon: There is a round core-shaped ring around the dots of an ink in the printed product.

the reason:

<1> The impurities in the ink adhere to the plate.
<2> The paper dust is peeled off and stuck on the plate.
<3> Dust particles or other materials on the printing press.

Countermeasures:

<1> Wash plate to remove impurities and replace new ink without impurities.
<2> The plate cleaning removes impurities and replaces paper that does not come off paper powder.
<3> Wash plate to remove impurities.

· Repository:

Phenomenon: Ink or ink mixture accumulates on the printing plate and like cloth, the printing picture area appears the partial ink is shallow or sends the flower.

the reason:

<1> The ink has poor fluidity after ink emulsification and does not transfer well.
<2> Paper powder or paper wool is mixed with ink and accumulated on the plate.

Countermeasures:

<1> Replace the ink with good water resistance, or add anti-water additives.
<2> Replace paper with low paper dust.

· Printing plate non-graphic area dirty:

Phenomenon: There is ink on the non-graphic area visible on the print.

the reason:

<1> The ink is not emulsified after being emulsified and emulsified on the plate.
<2> The fountain solution has a large surface tension, and the non-graphic area of ​​the plate is not well inked.
<3> Ink roller and plate pressure are too large.

Countermeasures:

<1> Replace the ink with good water resistance.
<2> Increase the IPA content.
<3> Adjust the ink roller and layout pressure.

· Off-page:

Phenomenon: In the printing area, the graphics area is poorly inked, and the print density is reduced or the image is not full.

the reason:

<1> The plate is not sensitive to grease.
<2> The paper powder that has come off the surface of the paper is worn by the plate surface.
<3> Insufficient printing pressure causes the image film of the plate to be worn off.
<4> Too much of the pH solution in the fountain solution causes the plate to corrode and the graphic comes off.

Countermeasures:

<1> Replace the new version.
<2> Replace better quality paper and use less viscous ink.
<3> Adjust the pressure, reduce wear.
<4> Pay attention to the adjustment of the fountain solution and add the PH solution at a reasonable ratio.

·Water roller stick ink:

Phenomenon: The ink on the transfer roller of the printer.

the reason:

<1> The ink is resistant to poor ink emulsification.
<2> Water roller and plate pressure are not normal.

Countermeasures:

<1> Replace the ink with good water resistance.
<2> Adjust the water roller pressure.