Engraving gravure printing is to first fill the concave part of the printing plate with ink, and then wipe (wipe) off the ink on the non-graphic part (surface area of the printing plate), and then imprint it on the substrate.
Since most of this printing method is to print securities with relatively high value, the printing materials are also high-grade paper, so the disadvantages brought or caused by paper are almost very few.
In engraving gravure printing, most of the printing failures are caused by (1) the ink itself; (2) caused by poor wiping process; (3) other reasons in the printing process.
(1) Poor Filling (Poor Filling).
1. Phenomenon: The inking roller gives a lot of ink, but it cannot be satisfactorily filled into the inking hole of the gravure.
2 Reason: Poor rheology of ink. Ink is too thick.
3. Solution: Use dilute varnish or high boiling point solvent to properly dilute and remove the ink. Use ink with good rheology.
(2) Breaks In Fine llnes.
1. Phenomenon: The thin lines of printed dramas are discontinuous and sometimes disconnected.
2. Reason: The oiler is too viscous and too thick to be suitable. It may also be that the oil is too thin.
3. Solution: Dilute the ink properly with thin varnish or high boiling point solvent. If the ink is too thin, you can add some thick ink or add some fillers and mix it finely with a three-roller machine.
(3) Smearing, also known as Smearing.
1. Phenomenon: There are traces of oil volume on the non-graphic part of the printing plate, which is transferred to the blank area of the paper.
2. Reason: The oil is too viscous and thick. Ink is too long.
3. Solution: Use thin varnish or high boiling point solvent to lighten the ink slightly. Add some fillers to the ink, and mix it with a three-roll machine. Carbon dioxide can also be used as filler.
(4) Floating dirty (Tintlng).
1. Phenomenon: The entire non-India area (blank part) presents a dull color.
2 Reason: It may be that the pigment particles used in the ink are relatively fine and the color is relatively strong: this phenomenon occurs when the defect of the layout i is larger than the pigment particles, but it is easier to wipe the plate when it is smaller than the pigment particles.
3. Solution: Use different materials and different fillers to prepare ink (that is, don't use only one pigment or filler). Generally speaking, the crystal shape of the pigment is easier to wipe the plate than the spherical one. In the traditional engraving gravure oiler, blue ink is a variety that is not easy to nickel.
(5) Insufficient ink (Starving).
1. Phenomenon: After the plate, the oil reed wheat surface in the economizer hole forms a concave moon surface slightly lower than the surface of the printing plate. If the amount of ink in the intaglio hole of the gravure plate is not enough after the plate is wiped, the printed matter will appear Weaker, this phenomenon is called insufficient ink, also known as wiping too much or wiping out Wiping O).
2 Reasons: The rheology of the ink is poor, and the viscosity and elasticity are too large. Poor wiping process. Sometimes it has nothing to do with the quality of plate making.
3. Solution: change the rheological properties of the ink, make the ink thicker and shorter, and improve the "coolness" of the oil ring. Improve the plate wiping process and improve the quality of plate making.
(6) Pulling out (Dragging out).
1. Phenomenon: After the plate is wiped, some ink remains on the back of the plate (that is, the rear of the plate in the direction of the wiper, see Figure 28-5), and there are rough burrs on one side of the printed product caused by the knot.
2. Reason: Generally, it is due to the small yield value of the ink and the small I thixotropy.
3. Solution: Improve the rheology of the ink, so that it has the characteristics of thick, short and non-sticky.
(7) Printed products are fluffy. Also known as flying edge (Spewing).
1. Phenomenon: the color on both sides of the printed matter is too thick and irregular.
2. Reason:The imprinting force on the paper is too large and the paper is pressed into the hole of the standard plate, or too much ink is left in the hole due to a bad nickel plate.
3. Solution: reduce the pressure on the paper, and use a pad tree with less elasticity in the rotary printing machine. Improve the method or process of holding the plate. The paper is slightly moistened.
(8) feathery (ea thering).
1. Phenomenon:The lines of the print are jagged and hairy. And there are burrs on both sides of the line, but not at the same point of the line i, nor on the printed matter.
2. Reason: The oil is caused by the force between the pores in the paper fibers.
3. Solution: Properly reduce the printing pressure. Moisten the paper slightly.
(9 ) Loss of density, line expansion and irregularity (Loss of Density Wid-ened And trregular Engra vlng).
1. Phenomenon: The density of the printed matter is not enough, and the thin lines become thicker but not neat.
2. Reason: The plane of the printing plate is worn out, causing the gravure to become shallow. The printing plate will wear the side wall of the ink hole during the wiping process.
3. Solution: Replace with a new printing plate. Redesign the ink, although some pigments in the ink have good working performance, but there are defects in the worn plate, and the pigment that is not harmful to the printing plate should be replaced.
