Causes and countermeasures of offset printing rotation
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Offset rotation takes over the market at its speed, but at the same time speed causes many corresponding printing problems. The following article lists several common rotary printing problems and their solutions.
· Flying ink:
Phenomenon: The ink flies out between the ink rollers in a mist to pollute the surroundings.
the reason:
<1> The ink is too thin and the viscosity is not suitable.
<2> The ink supplied to the ink roller is too thick or the ink roller oil film is uneven.
<3> Static electricity occurs.
Countermeasures:
<1> Adding a wax additive to shorten the ink and remove the viscosity.
<2> Reduce the ink supply amount and adjust the pressure of the ink roller to make the inner film uniform.
<3> Humidification.
· Dry on board:
Phenomenon: The ink is dried on the ink fountain or the ink roller.
the reason:
<1> The humidity at room temperature is too high and the temperature of the press is too high.
<2> The solvent in the ink evaporates too quickly or the drying inhibitor in the ink is small, and the ink is not suitable.
Countermeasures:
<1> Lower the room temperature and lower the circulating water temperature of the press roller.
<2> Replace the new ink.
·Ink roller deinking:
Phenomenon: The ink transfer amount is insufficient, the print density is lowered, and the metal transfer roller on the printer is white.
the reason:
<1> The ink is not good in water resistance.
<2> Printing water supply is too large, and the ink balance is out of balance.
Countermeasures:
<1> Add a water-resistant additive to the ink.
<2> Reduce the amount of water supply and adjust the ink balance.
·Ink fountain deinking:
Phenomenon: The ink is separated from the ink transfer in the ink fountain, the ink transfer amount is insufficient, and the print density is lowered.
the reason:
<1> Ink fluidity is not good.
Countermeasures:
<1> The ink in the fountain is often stirred to maintain its proper fluidity.
<2> Replace the ink with good fluidity.
·Pull hair
Phenomenon: The print has white spots or a roller that tears the paper off.
the reason:
<1> The viscosity of the ink is too high.
A. The ink itself is highly viscous.
B. If the temperature of the printing machine is too high, the ink solvent will volatilize and the viscosity of the ink will increase.
C. The printing room temperature is too low, and the ink temperature is low to make the ink highly viscous.
<2> The printing roller is too much pressure on the paper.
<3> Paper strength is not good.
Countermeasures:
<1> Reduce the viscosity of the ink.
A. Add a proper amount of high boiling point solvent.
B. Decrease the temperature of the printing syrup and the circulating water of the ink roller to cool the printing machine.
C. Increase the room temperature or preheat the ink at standard room temperature.
<2> Adjust the pressure of the printing roller.
<3> Replace the paper with better strength.
Ring white spot:
Phenomenon: A circular nucleus in the print surrounds 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 press.
Countermeasures:
<1> Washing removes impurities and replaces new inks without impurities.
<2> Wash the cloth to remove impurities and replace the paper that does not lose the paper powder.
<3> Washing to remove impurities.
Stack version:
Phenomenon: In the printing plate and like the cloth to accumulate ink or ink mixture, the printed image area appears partial light or hair.
the reason:
<1> The ink has poor fluidity after emulsification of the ink, and the transfer is not good.
<2> Paper powder or paper wool is mixed with ink and deposited on the layout.
Countermeasures:
<1> Replace the ink with good water resistance or add a water-resistant additive.
<2> Replace paper with less paper dust.
The non-image area of the plate is dirty:
Phenomenon: In the printed matter, you can see that there is ink in the non-image area.
the reason:
<1> The ink is resistant to water and is not emulsified and sticks to the hydrophilic surface.
<2> The surface tension of the dampening solution is large, and the non-image area of the plate is not good for ink.
<3> The 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 the plate pressure.
Off the version:
Phenomenon: In the printed version of the graphic area, the ink is poorly printed, the print density is reduced or the graphic is not complete.
the reason:
<1> The plate is not sensitive to grease.
<2> The paper powder that has fallen off the surface of the paper is worn against the layout.
<3> The printing pressure is too strong and the pattern film of the plate is worn away.
<4> Too much PH liquid in the dampening solution causes the plate to corrode and the image to fall off.
Countermeasures:
<1> Replace the new version.
<2> Replace paper of better quality and use less viscous ink.
<3> Adjust the printing pressure to reduce wear.
<4> Pay attention to the adjustment of the dampening solution and add the PH solution at a reasonable ratio.
·Water roller sticky ink:
Phenomenon: The water transfer roller of the printing press has ink.
the reason:
<1> Ink emulsification of ink which is not resistant to water.
<2> The water roller and plate pressure are not normal.
Countermeasures:
<1> Replace the ink that is resistant to water.
<2> Adjust the water roller pressure.
· Poor overprinting:
Phenomenon: The back color sequence ink is not well printed or overprinted.
the reason:
<1> The back color ink is more viscous than the previous ink and the previous color ink is pulled off.
<2> After the color sequential printing is too large, the front color ink is pulled off.
Countermeasures:
<1> Change the color sequence or reduce the viscosity of the back color ink.
<2> Reduce the adjusted color sequence printer press.
Poor drying:
Phenomenon: The ink has poor drying properties and there is a sticking phenomenon on the cooling roller.
the reason:
<1> The temperature of the paper reaching the box is not high enough, so a considerable amount of solvent in the ink cannot be removed.
<2> The temperature of the roll paper after printing is not good.
<3> The paper used is too poorly absorbed or the amount of printed ink is too large.
Countermeasures:
<1> Increase the paper temperature or lower the printing speed.
<2> Lower the cooling drum temperature.
<3> Reduce the amount of ink supplied or use absorbent paper.
Paper folding:
Phenomenon: The printed product will fold after folding.
the reason:
The oven temperature is too high to cause severe dewatering of the paper.
Countermeasures:
Reduce the oven temperature.
Bad friction resistance:
Phenomenon:
The printed product is not resistant to friction and fades.
the reason:
<1> The oven temperature is low and the thermosetting ink is not completely dried.
<2> The pH of the dampening solution is too low and the printed product is poorly dried.
<3> Paper absorbs strong material and penetrates too much
<4> There are few anti-friction additives in the ink.
Countermeasures:
<1> Increase the oven temperature to make the prints dry thoroughly.
<2> Increase the pH of the dampening solution.
<3> Select a paper that is moderately absorbent.
<4> Replace the new ink and add the abrasion aid.
Poor gloss:
Phenomenon: The printed product is not bright enough and the gloss is low.
the reason:
<1> The temperature of the supply box is too high, which causes the binder in the ink to become thinner and the paper to penetrate too much.
<2> The print is not completely dry.
<3> The amount of ink is insufficient or the gloss of the paper itself is low.
Countermeasures:
<1> Lower the oven temperature and adjust the appropriate paper surface temperature.
<2> Adjust the temperature and printing speed to make the print completely dry.
<3> Select high-gloss paper to increase the amount of ink in the print.
Ghosting:
Phenomenon: Two or more identical prints appear on the print.
the reason:
<1> Mechanical ghosting: due to loose plates or blankets.
<2> The overprinting of the overprinting color sequence is not allowed.
Countermeasures:
<1> Adjust the plate and blanket.
<2> Adjust the printing machine rules, improve the overprinting accuracy and change the printing color sequence.
Printed products are not flat:
Phenomenon: The print is not flat or the printed cross section is wavy uneven.
the reason:
<1> The amount of water supplied by printing is too large to deform the printed matter.
<2> The paper feed force of the printing machine is too strong to deform the paper.
Countermeasures:
<1> Reduce the amount of water supplied during printing.
<2> Adjust the tension of the press's tension roller.