Analysis of printing failure of the hottest plasti

2022-09-22
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Failure analysis of plastic gravure printing ink Poor ink transfer and dot loss are common and the most difficult to distinguish faults in gravure printing. "Technology is the best in the world" 1 has always been our creed, so we should fully consider a variety of factors and take targeted measures to deal with them when dealing with them.

1. Blocking

in gravure printing brush, the blocking phenomenon is generally manifested as: the light dot version cannot be transferred (such as human skin color) ; The ink transfer amount of deep dot version is reduced, usually from 50% - 70% to 20% - 30%

causes:

① during printing, due to the increase of ink viscosity caused by solvent volatilization, the ink cannot enter fine holes or lines, making the ink gradually dry and solid, resulting in blocking

② in printing, the distance between the doctor blade and the plate cylinder was too large or the angle was unreasonable in the late 1990s; Due to the large diameter of the plate cylinder or insufficient depth into the ink tank, the hot air blown out of the drying equipment will affect the plate cylinder and also cause blocking. This situation is very common in domestic printing machines

③ the engraving depth and angle of the printing plate hole are inappropriate

④ the printing environment temperature is too high, which makes the solvent volatilize too fast, resulting in blocking

⑤ with the addition of curing agent series of inks, with the extension of time on the machine, the ink solidifies in the printing plate hole, gradually reducing the depth of the printing plate, resulting in blocking

⑥ the ink formula design is unreasonable, and the solvent with too fast drying speed is used

solutions:

① adjust the ink drying speed, and select slow drying solvent according to the actual situation

② add ink blending oil to improve and improve the fluidity of ink

③ after printing, clean the printing plate immediately

④ according to the actual printing situation, add appropriate solvents in time to try to ensure the consistency of ink printing viscosity

⑤ redesign the ink formula, reduce the initial dryness and dryness of the ink, and increase the fluidity and transferability of the ink

⑥ for blocking caused by curing agent, do not add or add less curing agent as much as possible; If you really need to add curing agent, you should always check whether there is blocking and deal with it in time

2. Poor ink transfer

in printing, due to poor transfer, the amount of ink transferred to the plastic film cannot meet the requirements of the original design and the color concentration or color saturation of the standard printing sample, resulting in printing failure

causes:

① caused by blocking, the drying speed of ink on the printing plate is too fast

② the selected ink does not match and cannot be bonded and attached to the plastic film

③ incorrect ink formula design has led Chinese plastic machine enterprises to expand the development of emerging markets for extruders in recent years, resulting in light ink color or insufficient color saturation of the ink itself

solutions:

① for the faults caused by printing blocking, analyze the causes of blocking and take corresponding countermeasures

② change to the matching ink type

③ improve the ink formula and select appropriate raw materials, such as pigments with strong color saturation and coloring power and resins with good transferability

3. Dot missing

in the printing process, the uniform flat on the printing plate can't be leveled because the ink can't flow, and the dots appear alone, forming a filter shape, and even dot missing. Generally, this phenomenon is more obvious from the second color group

causes:

① the ink viscosity or yield value is too high, resulting in poor ink transfer

② the ink dries too fast and is not evenly distributed on the printing plate, so it dries and solidifies too early

③ the wettability between the ink and the printing plate is poor (the surface tension is inconsistent), and the transferred ink is not easy to spread

④ the pressure of the scraper is high, while the pressure of the printing cot is insufficient

⑤ the printing plate line is too thick, the hole spacing is large, and the ink is not easy to spread

solutions:

① reduce the viscosity of the ink and improve the transferability of the ink. It is recommended to use 20# additives dedicated to gravure ink

② adjust the position of the doctor blade holder to shorten the distance between the doctor blade and the plate cylinder

③ use slow drying solvent to reduce the drying speed of ink and improve the point increase rate

④ adjust the pressure of scraper and printing cot

⑤ remake the plate to change the shape and angle of the hole

⑥ use low viscosity ink

Author: taking into account the research of major policies, major projects and important work arrangements, Wu Wen

reprinted from: Printing Technology

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