Causes and solutions of common faults in the hotte

2022-08-11
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Causes and solutions of common faults in offset printing

offset printing uses the principle of immiscibility of oil and water to make the graphic part of the printing plate lipophilic and hydrophobic, and the blank part hydrophilic and hydrophobic, so as to achieve the purpose of printing reproduction. Because the printing plate surface must accept both ink and moisture during the printing process, in the "4+2" modern industrial system that Jiangbei new area focuses on developing, the common faults of offset printing are related to ink and fountain solution, which are mainly manifested in the phenomena of paper fuzzing, printing product color lightening, ink powder color loss, adhesion, slow drying, ink flying, paste conversion, rubber stacking, ink stacking roller, oil dirt, dirty version, etc. In view of the above phenomena, most of the elimination methods should start with ink and fountain solution and their related factors

(1) paper fuzzing. The main reason is that the ink viscosity is too large or the paper strength is poor. The elimination method is to add an appropriate amount of ink remover to reduce the viscosity of the ink, and use paper with high surface strength to reduce the speed of the printing machine

(2) the color of the print becomes lighter. The main reason is that the thixotropy of ink is too large and the viscosity is too small. The elimination method is to add new ink with high fluidity or resin inking oil with high viscosity

(3) ink chalking and fading. The main reason is that the connecting material in the ink is insufficient and the viscosity is low σ 0.2 means it is too small, and the drying is advanced basic materials, key strategic materials, cutting-edge new materials are too slow, and the water resistance is too poor. The ink absorption of paper is too strong, and the acidity of fountain solution or paper makes the pointer return to zero and change greatly. The elimination method is to speed up the drying speed of the ink, add an appropriate amount of red drying oil to the ink, reduce the acidity of the fountain solution, and reduce the water supply

(4) adhesion. The main reasons are that the powder amount is too small, the paper pile is too high, and the ink curing is too slow. The elimination method is to increase the amount of powder spraying, reduce the stacking thickness of finished products, choose the amount of fast curing oil, or add polyethylene wax to the ink

(5) drying is too slow. The main reason is that the drying agent in the ink is insufficient, and the paper or fountain solution is too acidic. The elimination method is to add an appropriate amount of desiccant into the ink and adjust the pH value of the fountain solution

(6) flying ink. The main reasons are that the ink layer is too thick, the viscosity is too small, or the ink roller installation is unreasonable. The elimination method is to use a thicker ink, reduce the amount of ink, check whether the ink roller installation is reasonable, eliminate static electricity, and improve the indoor temperature

(7) paste. The main reasons are that the ink proportion is too large, the powder content is too high, the particles are coarse, the viscosity is too small, the water resistance is poor, the ink roller and the printing plate ink layer are too thick, and the paper is de powdered. The elimination method is to increase the ink viscosity or add new thick ink to adjust or replace the paper

(8) stack rubber. The main reasons are that the ink has poor water resistance, small viscosity, insufficient connecting materials, poor transfer, or paper de powdering. The elimination method is to adjust the proportion of ink, add ink with higher coloring power, improve the water resistance of ink or replace better paper

(9) ink stacking roller. The main reason is that the ink has poor water resistance, too high viscosity, and too much water supply of fountain solution. The elimination method is to add new ink, reduce the water supply of the fountain solution, or add isopropanol to the fountain solution to improve wettability and increase volatility

(10) dirty oil. The main reason is that the water resistance of the ink is too poor, the viscosity is not enough, and the oil is too strong. The elimination method is to increase the viscosity of the ink, add a small amount of extra oil, use fast drying bright ink, add a small amount of light magnesium carbonate to the ink to reduce the oiliness, or try not to use lake pigment ink

(11) dirty version. The main reasons are that the ink is too soft, the viscosity is small, the water resistance is too poor, the acid and Arabic glue in the fountain solution are insufficient, and the water glue is not clean. The elimination method is to use ink with good elasticity, add an appropriate amount of Arabic resin glue to the fountain solution to improve the acidity of the fountain solution, add an appropriate amount of isopropyl alcohol, and thoroughly clean the wet version roller

(author/Xu Xihong)

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