Analysis of common problems of the hottest plastic

2022-08-09
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Analysis of common problems of plastic gravure printing

plastic gravure printing is vulnerable to various variable factors. Under the condition that it is impossible to greatly update the existing hardware equipment of the enterprise, how to adopt innovative process technology to solve the problem has been one of the topics jointly studied by insiders for a long time. Based on the author's superficial understanding of plastic gravure printing, this paper talks about the problems of gravure printing plate and ink for reference

first, point loss problem

someone once listed point loss as one of the four evils of gravure printing, which is enough to explain that point loss is a frequent problem in gravure printing. After long-term practice and observation, I think there are three main reasons for the loss of points

1. printing plate problem

when there is a bit of loss and unclear hierarchy in production, we should first consider the problem of printing plate itself. The production process of gravure plate is relatively complex, and limited by economic conditions. At present, most packaging and printing enterprises do not have their own plate making companies, plus they do not have a special proofing machine to conduct proofing inspection on the printing plate before it is put on the machine, so there are many problems with the printing plate. In the printing process, if there is a point loss, for the printing plate, the solutions are:

(1) wipe the part on the printing plate with a special plate wiping agent, which can solve the point loss caused by blocking

(2) if wiping the printing plate cannot solve the problem, use a magnifying glass with a light source to carefully examine the printing plate to see whether it has been carved or corroded during the production of the printing plate. If there are defects in the production, it is necessary to remake the plate

(3) when making printing plates, analyze the originals according to the equipment owned by the printing factory and the printing materials used. If necessary, the highlight parts that are easy to cause point loss should also be specially treated, which is usually called deepening

2. ink problems

in addition to matching with the printing material, gravure printing also requires the known viscosity and initial dryness of the ink. In case of point loss, after excluding the printing plate factors, the solutions for the ink are:

(1) reduce the viscosity of the ink, so that the ink has good leveling, so as to improve the wettability of the ink to the printing plate

(2) improve the initial dryness of the ink, that is, reduce the initial dryness of the ink and extend the drying time. Some slow drying solvents, such as xylene, can be added in the specific operation, or the ink can be changed

(3) do not add air to the printing plate during the printing process

3. printing plate speed and pressure

when the point is lost and the level is unknown, it can also be solved by accelerating the printing speed and appropriately increasing the printing pressure. However, due to equipment limitations, it is usually not easy to completely solve practical problems

second, the problem of ink adhesion

the main factors affecting ink adhesion are:

(1) the influence of ink composition on ink adhesion

generally, the main factor affecting ink adhesion is that the resin used in the production process of ink does not have the best wettability to the substrate, so the adhesion of the ink produced with this kind of resin is poor

(2) the influence of the surface energy of the substrate on the adhesion of the ink

in order to ensure a certain adhesion fastness, the substrate must be surface treated before printing to make its surface energy reach more than 0.038n/m

(3) the influence of the relative humidity and temperature of the printing workshop on the ink adhesion

after long-term observation and experiment, I believe that with the increase of the relative humidity of the environment, the adhesion has an upward trend at the beginning, but as the humidity continues to rise, the adhesion begins to decline again. This shows that there is a critical value of relative humidity suitable for printing, but due to restrictions, I failed to measure the specific value. Temperature is an important condition in gravure printing, which affects both drying and the tension of printing materials. If the temperature is set too high, it will not only affect the vertical overprint accuracy, but also reduce the adhesion due to the "fast" drying of the ink on the substrate. Therefore, after long-term experiments, I believe that the environmental temperature suitable for printing should be controlled at 30 ℃, mainly including the advantages of new materials in furniture adhesives, furniture sponges, furniture surfaces, and household coatings. If the tensile test is carried out, the sealing volume of the oil pump can be used in different oil suction chambers at a certain instant; The extension of new intermediate materials and new intermediate technologies to terminal utilization is below. The drying temperature is different due to the influence of printing materials, ink layer thickness, printing speed and other factors. The general principle is not to set too high

(4) influence of ink layer thickness on ink adhesion

in order to clarify the relationship between the two, I used the same ink to peel off the field version and layered version prints, and found that the adhesion decreased with the increase of ink layer thickness

III. Influence of ink on the service life of printing plates

in actual production, in order to ensure the stability of the hue of printing products and the good inkability of printing plates, a certain amount of residual ink must be left in the ink bucket after each batch of live parts is printed. These residual ink will infiltrate a large amount of impurities after long-term reuse, such as sand particles falling off the metallographic sandpaper when grinding the doctor blade, abrasives and dust of the printing plate and the doctor blade, etc. If these impurities are not disposed of in time, they will combine with the binder and other components in the ink to produce deposition, which will not only be prone to knife lines, but also seriously damage the surface finish of the printing plate, and significantly reduce the printing resistance of the printing plate. What do you know about the ceramic film four point bending tester?, Affect the service life of the printing plate. Therefore, under the principle of saving, these residual inks should be filtered regularly with more than 250 mesh silk used for silk printing. If possible, the ink factory can re filter and grind the old ink before using it. This can prolong the service life of the printing plate

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