Common printing faults and solutions of the hottes

2022-09-19
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Common printing faults of Gravure plastic ink and their solutions

first, reverse adhesion:

phenomenon: after printing with ink, the printed matter will stick to the back of the printing substrate, and the pattern will be damaged, which will usually cause the scrapping of the product. This phenomenon is called reverse adhesion

reasons: (1) poor drying; (2) High pressure during winding; (3) The temperature is too high during winding; (4) The film is electrostatic; (5) Solvent residue

solutions: (1) touch the pattern of the print with your hand to see if it is not dry. If the imprint is not dry, replace with a faster drying solvent; Accelerate the drying speed of ink. If the surface of the ink is dry but not completely dry, adjust the proportion of the solvent appropriately, reduce the amount of fast drying solvent, increase the amount of slow drying solvent appropriately, and increase the drying hot air temperature at the same time. Make sure the ink is completely dry before winding. (2) Check whether the winding pressure is too large, whether the film is deformed during winding, and appropriately reduce the pressure during winding. The printed matter should be placed vertically after winding, and should not be put down and pressed onto the printing part; (3) Check whether the temperature of the film returns to normal temperature during winding. If the film is still warm during winding, let the drying system of the printing machine blow cold air before winding to ensure that the temperature of the film returns to normal temperature before winding; (4) Touch the printing surface of the film with your hand to see if the film is seriously electrostatic. If it is electrostatic, you need to check the ground wire of the printer to ensure that the ground wire is connected; (5) If the ink is dry, press a large area of the printing surface with your hand to see if the imprint sticks to your hand. If it sticks to your hand, it is affected by residual solvents. You should adjust the solvents used and their proportions appropriately

second, there is a phenomenon of "water spots"

in the printed matter: after printing with ink, the printed matter appears to be many water spots, or in the shape of fine-grained water lines. The pattern is not full and lifelike

reason: when the ink is printed on the machine, the machine speed is slow, and the ink is too thin

solution: improve the printing speed; Or add the original ink to improve the viscosity of the ink

III. blocking of printing plate points

phenomenon: after printing with ink, it is found that there will be a lot of dots on the printed matter. Before measurement, a standard block is needed to calibrate the hardness tester, but it does not appear to be watery. Instead, there is a phenomenon of more dry points and exposure

reason: timely publicize the achievements of industrial development, which is due to ensuring that there is more than 70cm space around the experimental machine for experiments and normal protection. The printing speed is not high, and the ink dries too fast, blocking the points of the gravure

solution: wipe the gravure with diluent first, and then increase the printing speed to print, or add a slower drying diluent to slow down the drying speed

IV. albinism of printed matter

phenomenon: after printing, it is found that there is a fog like white layer on the surface of printed matter, which causes the printing effect to be not obvious and lifelike. It is called albinism, or whitening

cause: the main cause of albinism is the high humidity of the environment or the imbalance between true and false solvents

solution: reduce the humidity of the environment; Strengthen the drying of hot air; Use slow drying solvent and add real solvent with high boiling point

v. biting

phenomenon: during overprinting; The color of the previous printing will be glued down by the next ink, which will cause the ink in the ink tank to gradually change color

reason: the imprint of the previous process is not completely dry; There is too much pressure in the next printing

solution: increase the drying speed of the previous ink, increase the hot air temperature and air supply volume, and ensure that the print is dry by the next ink; Reduce the printing pressure and the viscosity of the ink

VI. solvent precipitation

phenomenon: when the ink is printed on the machine, it is found that the ink particles precipitate after adding the solvent, without viscosity or fluidity

reason: the ink thinner selected is improper, and the solvent is not fully stirred

solution: contact the ink manufacturer and select the correct diluent to dilute the ink; When diluting the ink, do not add the solvent one by one, but prepare the mixed solvent first, and then add it to the ink (it needs to be added while stirring if necessary). Note that after adding the solvent, it should be fully stirred

VII. First of all, it is caused by the poor printing fastness of the surface/interface of the implanted material

phenomenon: the ink is printed on the plastic film, and the printed matter is easy to be stuck down by peeling off with adhesive tape

cause: poor corona treatment of polyolefin film; The compatibility between the ink and the printed material is poor, and the mixed solvent ratio is wrong; The relative humidity of the printing workshop changes greatly; The printability of the plastic film itself is very poor, and it still does not meet the requirements after corona treatment

solution: check whether the surface tension of the plastic film reaches more than 40 dyne/cm2; Adjust the solvent ratio or change the ink; Try to control the humidity of the printing workshop between%, but not too low, otherwise it is easy to generate static electricity. The room temperature is best controlled between ℃, and keep the environment clean and ventilated. Replace the printed materials used

reprinted from: ink information

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