Poor adhesion of ink on substrate
1.1 Ink adhesion mechanism wetting: Adhesion fastness is the result of the interaction between the molecules of the printing substrate film and the ink connecting material.
Compatibility: The polarity of the ink connecting material is similar to that of the substrate, resulting in good compatibility. (Be sure to choose ink that matches the printed material).
1.2 Reasons and countermeasures for weak adhesion: substrate factors.
a. The corona treatment on the surface of the substrate is not sufficient to achieve the required tension, or the treated substrate surface may fail due to poor storage environment and prolonged storage time, resulting in surface tension attenuation.
The general requirement is that the surface tension of PP and PE should be ≥ 38mN/m, PET should be ≥ 50mN/m, and NY should be ≥ 52mN/m. Before use, the surface tension of each batch of film should be checked.
b. During processing, most substrates are added with certain lubricants, anti-static agents, moisture-proof agents, etc. These additives slowly penetrate from the film to the surface over time, forming a weak interface layer on the film surface, which affects the ink adhesion. Therefore, the film should be used within its shelf life and surface tension should be tested before use. Can be tested with a dyne pen. The factor of substrate moisture absorption. For example, materials such as PA, PVA, and PT are prone to moisture absorption and reduce adhesion. These substrates should be stored under good conditions (temperature and humidity control) and fully preheated before use. The ink was of the wrong model and mixed with different types of ink.
There are many types of ink for gravure printing, including surface and inner ink. Different materials correspond to different inks, and various specialized inks must be used accordingly. Otherwise, the adhesion strength is not enough. Before production, the operating process instructions should be checked. Ink whitening. Ink deterioration and whitening cause an extreme decrease in adhesion. Insufficient ink drying. Insufficient drying, excessive residual solvents inside, and a certain drying temperature are extremely beneficial for improving the adhesion of some resin connecting materials.

Overprinting error
Overprinting errors are mostly common defects in printing, and their phenomenon is that in the multi-color printing process, each color cannot completely overlap and there is a certain deviation.
2.1 Personnel Quality: Due to the objective existence of color matching errors, employees are required to have extremely strong work abilities. Printing is a meticulous job that must be done with care, attention to detail, and a sense of responsibility. During work, it is important to conduct self inspection and self inspection, observe from multiple perspectives, and promptly identify any issues.
2.2 Equipment Factors The accuracy and performance of the entire equipment, tension control for printing, heating and air supply system, and the coordination of embossing rubber rollers, plate rollers, plate shafts, guide rollers, and other systems determine the temperature, pressure, parallelism, elongation, and coiling during printing. The color matching system itself limits its accuracy. The color matching photoelectric device should be well maintained and operated correctly. For example, if the halogen light source is weak, the fiber optic or halogen bulb should be replaced, and the distance between the reflector and the scanning head should be adjusted correctly, usually around 8mm. Inappropriate increment of the plate roller can lead to inaccurate vertical color matching, rubber deformation of the embossing roller, and insufficient elasticity. Keep the pressure roller in good condition.
2.3 The tension setting of the substrate in the operation process is unreasonable, the tension is too small, the substrate is loose, and the vertical and horizontal color matching is not accurate; The tension is too high, causing lateral shrinkage of the substrate and unstable vertical color matching. Adjust the tension accordingly. The temperature is not suitable, especially when the oven temperature is too high and the cooling roller temperature is too high, causing deformation of the film. For uneven films, the preheating box temperature should be appropriately increased. The imbalance of air intake and exhaust in the oven causes the film to shake in the oven. An anemometer should be used to measure and control the air intake and exhaust. If the installation of the plate roller is not appropriate and there is eccentricity, it is necessary to clean the ink on the plug before installing the plate roller.
3.1 Reasons for scraper line marks ① Line marks without ink. The main reason is that hard inorganic impurities such as sand are mixed in the ink, and these hard particles are embedded in the blade edge, causing line marks. Sometimes these types of scraper marks also appear as dashed lines, which can easily damage the printing and scraper.