custom hard-cover book and soft-cover book are printed with various packaging materials as the carrier. Decorative patterns, patterns or words are printed on the packaging to make the product more attractive or more descriptive, thus transmitting information and increasing sales. Including packaging cartons, packaging bottles, packaging cans, etc. custom hard-cover books and soft-cover books occupy a large proportion in the printing industry and packaging industry, and are an indispensable part of the packaging project. There are letterpress printing, plate printing, gravure printing, screen printing, hole plate printing and other printing methods. The main elements of printing are paper, ink, color, etc. custom hard-cover books and soft-cover books need to take into account economic, environmental protection and other issues, and need to be able to complete and well express the information to be printed.

First, the adhesion of ink on the substrate is poor

1.1 Ink adhesion mechanism

Wetting: Adhesion fastness is the result of the forced interaction between the printing substrate film and the ink binder.

Compatibility: The polarity of the ink connecting material and the substrate is similar, and the compatibility is good.

1.2 Reasons and countermeasures for weak adhesion

The corona treatment degree of the substrate surface is not enough, the tension is not reached, or the treated substrate surface is damaged due to poor storage environment and too long storage time, resulting in surface tension attenuation and failure. General requirements PP, PE surface tension ≧38mN/m, PET≧50mN/m, NY≧52mN/m. The surface tension of each batch of film should be checked before use. The substrate is mostly added in the processing of certain lubricants, antistatic agents, moisture-proof agents, etc. These additives slowly penetrate from the film to the surface over time, forming a weak interface layer on the surface of the film, affecting the ink adhesion. Therefore, the film should be used within the validity period and the surface tension should be measured before use. Test with a Dyne pen. Substrate moisture absorption factor. For example, PA, PVA, PT and other materials are easy to absorb moisture and reduce adhesion, such substrates should be stored under good conditions (temperature and humidity control) and fully preheated before use. The wrong type of ink was used. Different types of ink were mixed. There are many types of gravure ink, surface printing, printing ink, different materials correspond to different inks, a variety of special inks must be used, otherwise the adhesion fastness is not enough, before production should check the operation process instructions. Ink whitening. Ink deterioration, whitening, the adhesion is extremely reduced. The ink is not dry enough. Insufficient drying, internal residual solvent, in addition, a certain drying temperature for some resin joint adhesion is very favorable

Two, overprinting error

Most of the overprinting errors are common defects in printing, the phenomenon is that in the multi-color overprinting process, each color can not completely overlap, there is a certain deviation.

2.1 Personnel Quality

Because the color error is an objective existence, it requires employees to have strong working ability. Printing is a meticulous work, we must do hard, careful, responsible. When working, we should do a good job of self-examination, self-examination, multi-party observation, and timely detection of problems.

2.2 Equipment Factors

The accuracy and performance of the entire equipment, the overprinting tension control, the heating air supply system, the rubber roller, the plate roller, the plate shaft, the guide roller and other systems, these circumstances determine the temperature, pressure, parallelism, elongation, winding, etc., and the color system itself is the limit of its accuracy.

The color photoelectric device should be maintained and operated correctly. For example, the halogen light source is weak, the optical fiber or halogen bulb should be replaced, and the distance between the reflector and the scanning head is adjusted correctly, generally about 8mm.

The increase of the plate roller is not appropriate, easy to produce longitudinal miscoloration, rubber deformation of the imprinting roller, and insufficient elasticity. Keep the roller in good condition

2.3 Operation Process

The tension of the substrate is not reasonable, the tension is too small, the substrate is relaxed, and the color is not allowed. If the tension is too large, the transverse shrinkage of the substrate and the longitudinal coloring are unstable, and the tension is adjusted accordingly. The temperature is not suitable, especially the oven temperature is too high, the cooling roller temperature is too high to deform the film, and the preheating box temperature should be appropriately increased for the film that is not too smooth. The inlet and exhaust air volume in the oven is not balanced, causing the film to shake in the oven. The inlet and exhaust air volume is measured by anemometer and controlled. Plate roller installation is not suitable, such as eccentricity, before the plate roller installation must scrub the ink on the plug.

3.1 Causes of scraper line marks

Ink-free line marks. Mainly the ink mixed with hard inorganic impurities, such as sand, these hard particles embedded in the blade and caused line marks. Sometimes this type of scraper line marks are also dotted, and the appearance of this scraper line marks is easy to damage the printing and scraper. Thick continuous scraper line marks with ink. This is mainly due to some coarse soft particles or impurities that push up the scraper, or the blade of the scraper is damaged. This is the simplest and most common scraper line mark. This kind of scraper line marks generally appear in the printing roller dot is very shallow or uncarved dot part, hidden and present, great harm to product quality. The cause of this type of scraper line mark is more complex, and it has been explained from the aspects of ink, plate making, printing environment and so on for many years, but so far, none of them is more perfect. The better one is the "active particle hypothesis". Continuous filamentary blade marks. This kind of scraper line marks are small, like hair, often appear in the printing process, and it is difficult to observe on the printing press, until it is found that a large number of products have been issued, so the harm to the quality is great. This kind of scraper line marks can be divided into two kinds, one is soft and can be lightly wiped off with a bamboo knife, mainly caused by impurities; The other is the initial hair filamentous, and then slowly ribbon-like distribution, can not be wiped with a bamboo knife, the reasons are very complex, involving ink, plate making, environmental temperature, humidity, knife hardness and other aspects, the need for specific analysis and treatment. In general, there are probably the following aspects: plate roller. The surface finish of the roller is not good, the hardness of the chrome coating on the surface of the roller is not enough, the plate roller is too smooth, and the non-lubrication effect is easy to produce. Inks. The fineness of the ink is not enough, the pigment particles are too large, and the granular impurities are mixed in the process of ink use. Ink dilution is not standard, resulting in solvent impact phenomenon; The antistatic property of the ink is poor, and the lubrication property of the ink is poor. The use of high hardness pigments will produce lines. The environment. The temperature, humidity and cleanliness of the air in the printing shop will also affect. For the scraper. A hard scraper produces more line marks than a soft scraper. In addition, if the scraper line mark can not be treated in time, it will produce a large bunch of scraper line marks around the line mark with the swing of the scraper.

3.2 Solution

When installing the knife, it must be smooth and careful. Before installing the knife, check whether there is a gap in the blade. After installing the knife, it must be carefully ground. It is strictly forbidden to mix the oil of the knife into the ink. The environment must be treated to reduce dust in order to eliminate the fault. The color printing environment should be kept closed as much as possible, and air filters can be installed and dust content verified, otherwise, it is difficult to produce high-quality products. The knife wire caused by the plate roller generally appears in the shallow part of the net, such as the rough version, the gradient is excessively uneven, and the net depth is inappropriate. Generally, it should be processed by using metallographic sandpaper, and pay attention to the uniform force when grinding the plate, and especially serious cases should be returned to the plate making factory. Reduce the viscosity of the ink, such as the viscosity is too large, the page ink dries too fast, relatively increasing the friction between the plate roller and the scraper, so that the scraper is difficult to scrape the page ink to form a knife wire. If the knife wire is caused by ink, generally due to the ink in the garbage or uneven ink dissolution caused, should be taken to filter the ink, re-select the solvent with strong solubility or change the ink.

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