Six, flying ink
Phenomenon: When the printing press is running, the ink is split between the ink rollers of the printing machine. The long ink forms long filaments. These filaments are broken into fine droplets and scattered in mist and distributed in the air of the printing shop.
the reason:
(1) Printing speed is too fast.
(2) Too much ink, the ink layer on the ink roller is too thick.
(3) The ink is too long and sticky.
(4) The ink roller is not properly installed or damaged.
Approach:
(1) Reduce the printing speed.
(2) Change the ink with high color density to reduce the amount of ink.
(3) Add wax additives to make the ink short and reduce the viscosity.
(4) Check the ink roller and open the ink fountain smaller. Adjust the ratchet wheel to make the rotation faster.
Seven, ink does not fall
Phenomenon: The ink lacks fluidity during printing and cannot be transferred from the ink fountain to the ink roller.
the reason:
(1) The yield value of the ink is too large, and the ink ink has a short flowability.
(2) Large thixotropy of ink.
Approach:
(1) Add a #3 varnish that can lengthen the ink, or a high-viscosity resin oil that improves the fluidity of the ink.
(2) Stir the ink often or install a stirrer in the ink fountain.
(3) Change the ink with good fluidity.
Eight, paper lint or powder off
Phenomenon: When printing, fiber or filler particles are dropped from the surface of the paper and piled up on the graphic of the blanket, so that the quality of the print is reduced.
the reason:
(1) Poor paper quality.
(2) The viscosity of the ink is high, or the viscosity is increased due to solvent evaporation in the ink.
(3) Printing speed is too fast. Printing pressure is too high, causing excessive friction between the paper and the blanket.
Approach:
(1) Change paper.
(2) Add #6 varnish or 05-92 detackifier to reduce the initial tack of the ink.
(3) Adjust printing pressure and reduce printing speed.
Nine, emulsification phenomenon: in the lithographic printing ink and fountain solution for high-speed extrusion contact, the ink and the fountain solution emulsification, the formation of oil-water emulsion. The fluidity and viscosity of the ink are changed, printability is deteriorated, drying is slowed, and printing failure occurs. In addition, when the oil-based emulsion in water is formed by emulsification, the ink particles are dispersed in the fountain solution to cause turbidity.
the reason:
(1) Polar substances and surfactants exist in the ink.
(2) Low viscosity oil is used.
(3) Wet liquid volume is large.
(4) The graphic area is small and the consumption of ink is small. The ink on the printing press is in contact with water for a long time to produce emulsification.
Treatment method: In the lithographic printing, the ink and fountain solution should form a moderate oil-in-water emulsion in order to make the printing run smoothly. If emulsification becomes a print failure, take various countermeasures to solve the problem.
Ten, ring white spot
Phenomenon: There is a ring of white spots in the printed graphic.
the reason:
(1) The ink drying film is adhering to the ink and attached to the printing plate blanket.
(2) Paper powder, dust, and other foreign materials mixed with ink.
Approach:
(1) Do not mix the ink dried film with the ink when removing the ink from the tank.
(2) Replace the paper.
(3) Carefully clean ink fountains, rollers, blankets, and plates.
(4) It was found that the ink was replaced when ink was present in the ink.