Editor's note: Offset printing rotates to occupy the market at its speed, but at the same time, the reason for the speed will also cause many corresponding printing failures. The following article lists several common web printing faults and their solutions.
· Fei Mo:
Phenomenon: The ink scatters out like mist between the ink rollers and pollutes the surroundings.
the reason:
<1> The ink is too thin and sticky.
<2> The ink supplied to the ink roller is too thick or the ink film of the ink roller is uneven.
<3> Static electricity occurs.
Countermeasure:
<1> Add wax additives to make the ink shorter and remove tack.
<2> Reduce the ink supply and adjust the ink roller pressure to make the inner film even.
<3> Humidification.
· Machine drying:
Phenomenon: The ink dries on the ink fountain or ink roller.
the reason:
<1> The room temperature and humidity are too high and the printer temperature is too high.
<2> The solvent in the ink evaporates too fast or the drying inhibitor in the ink is low, the ink is not suitable.
Countermeasure:
<1> Lower the room temperature and lower the circulating water temperature of the printing press ink roller.
<2> Replace with new ink.
· Ink roller deinking:
Phenomenon: Insufficient amount of ink transfer, the concentration of the printed matter is reduced, and the metal transfer roller on the printing machine is white.
the reason:
<1> The ink has poor water resistance.
<2> The amount of printing water supply is too large, and the balance of water and ink is out of balance.
Countermeasure:
<1> Add water resistance additives to the ink.
<2> Reduce the water supply and adjust the water and ink balance.
· Ink fountain deinking:
Phenomenon: The ink is separated from the ink transfer in the ink fountain, the amount of ink transfer is insufficient, and the concentration of the printed matter decreases.
the reason:
<1> Ink flowability is not good.
Countermeasure:
<1> Stir the ink in the ink fountain frequently to maintain its proper fluidity.
<2> Replace the ink with good fluidity.
· Paper pulling phenomenon: The printed product has white spots or the printing roller tears the paper.
the reason:
<1> The ink viscosity is too high.
A. The ink itself has high viscosity.
B. Excessive printer temperature makes the ink solvent volatilize and the ink viscosity increases.
C. The printing room temperature is too low, and the low ink temperature makes the ink viscous.
<2> The pressure of the printing roller on the paper is too high.
<3> The paper strength is not good.
Countermeasure:
<1> Reduce ink viscosity.
A. Add an appropriate amount of high boiling point solvent.
B. Reduce the temperature of the printing syrup and the circulating water of the ink roller to cool the printing press.
C. Increase the room temperature or preheat the ink at standard room temperature.
<2> Adjust the printing roller pressure.
<3> Replace the stronger paper.
Ring white spot:
Phenomenon: There is a circular core in the printed product surrounding a small dot of ink.
the reason:
<1> Impurities in the ink stick to the plate.
<2> The paper powder falls off and sticks to the plate.
<3> Dust particles or other substances on the printing press.
Countermeasure:
<1> Wash the plate to remove impurities and replace with new ink without impurities.
<2> Wash the plate to remove impurities and replace the paper that does not lose paper powder.
<3> Wash the plate to remove impurities.
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Stacked version:
Phenomenon: Ink or ink mixture accumulates on the printing plate and leather-like cloth, and the local ink is light or blooming in the graphic area of ​​the printed product.
the reason:
<1> The ink has poor fluidity after emulsification and poor transfer.
<2> Paper powder or paper wool is mixed with ink and accumulated on the plate surface.
Countermeasure:
<1> Replace the water-resistant ink, or add water-resistant additives.
<2> Replace paper with less paper powder.
The non-graphic area of ​​the printing plate is sticky and dirty:
Phenomenon: Ink can be seen on the non-graphic area on the printed product.
the reason:
<1> The ink is not resistant to water, emulsifies, and sticks to the hydrophilic surface after emulsification.
<2> The surface tension of the fountain solution is large, and the non-graphic area of ​​the plate is not easy to stain ink.
<3> The pressure between the ink roller and the plate is too high.
Countermeasure:
<1> Replace the ink with good water resistance.
<2> Increase the IPA content.
<3> Adjust the pressure between the ink roller and the layout.
Reversion:
Phenomenon: The graphic area of ​​the printing plate is poorly inked, the density of the printed matter is reduced or the graphic is not correct.
the reason:
<1> The plate is not lipid-sensitive.
<2> The paper powder peeled off from the surface of the paper abrades the layout.
<3> The printing pressure is too strong and the graphic film of the plate is worn away.
<4> Too much PH in the fountain solution causes the printing plate to corrode and the graphics and text fall off.
Countermeasure:
<1> Replace with a new version.
<2> Replace the paper with better quality and use ink with lower viscosity.
<3> Adjust the printing pressure to reduce wear.
<4> Pay attention to the adjustment of fountain solution and add PH solution in a reasonable ratio.
· Water roller sticky ink:
Phenomenon: There is ink on the water transfer roller of the printing press.
the reason:
<1> Ink emulsification with poor water resistance.
<2> The pressure between the water roller and the plate is abnormal.
Countermeasure:
<1> Replace the water-resistant ink.
<2> Adjust the water roller pressure.
· Poor overprint:
Phenomenon: The over-sequencing ink overprinting is not good or overprinting.
the reason:
<1> The post-order ink is more viscous than the pre-package ink and pulls off the pre-ink.
<2> After the color sequence printing is too large, the color ink is pulled off.
Countermeasure:
<1> Change the color sequence or reduce the viscosity of the ink in the subsequent color sequence.
<2> Reduce the pressure of the color sequence printer after adjustment.
Poor drying:
Phenomenon: Ink drying is poor, and there is ink sticking on the cooling roller.
the reason:
<1> The temperature of the paper surface reaching the supply box is not high enough, so a considerable amount of solvent in the ink cannot be removed.
<2> The temperature cooling effect of the roll paper after printing is not good.
<3> The paper used is too poorly absorbent or the ink volume of the print is too large.
Countermeasure:
<1> Increase the paper temperature or reduce the printing speed.
<2> Lower the temperature of the cooling drum.
<3> Reduce the amount of ink supplied or use absorbent paper.
Paper cracking:
Phenomenon: The printed product will break when folded.
the reason:
The oven temperature is too high to make the paper dehydrated seriously.
Countermeasure:
Lower the oven temperature.
Poor friction resistance:
phenomenon:
Prints are not resistant to rubbing and fade.
the reason:
<1> The thermosetting ink is not completely dry when the oven temperature is low.
<2> The pH value of the fountain solution is too low, and the printed matter is poorly dried.
<3> The paper absorbs strong binders and penetrates too much. <4> The ink has less friction-resistant additives.
Countermeasure:
<1> Raise the temperature of the oven to allow the printed matter to dry completely.
<2> Increase the PH value of fountain solution.
<3> Select paper with moderate absorption properties.
<4> Replace with new ink and add anti-friction additives.
Poor gloss:
Phenomenon: The brightness of the printed product is not enough, and the gloss is low.
the reason:
<1> The temperature of the supply tank is too high, resulting in thinner connection material in the ink and excessive penetration into the paper.
<2> The print is not completely dry.
<3> Insufficient ink or low gloss on the paper itself.
Countermeasure:
<1> Lower the oven temperature and adjust the proper paper surface temperature.
<2> Adjust the temperature and printing speed to make the printed product completely dry.
<3> Select high-gloss paper to increase the ink volume of the printed product.
Ghost:
Phenomenon: Two or more identical marks appear on the printed product.
the reason:
<1> Mechanical ghosting: due to loose printing plates or blankets.
<2> Overprinting with poor color sequence is not allowed.
Countermeasure:
<1> Adjust the printing plate and blanket.
<2> Adjust the rules of the printing press, improve the accuracy of overprinting and exchange the color sequence of overprinting.
Print unevenness:
Phenomenon: The printed product is uneven or the cross-section of the bound product is wavy and uneven.
the reason:
<1> The printing water supply is too large to make the printed matter wet and deformed.
<2> The paper feed roller of the printing press is too stretched to deform the paper.
Countermeasure:
<1> Reduce the water supply during printing.
<2> Adjust the tension of the tension roller of the printing press.
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