Bar code printing technology of the hottest plasti

2022-08-15
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Complete solution of bar code printing technology for plastic packaging (V)

2. Version contamination

the non graphic part of the printing plate leaves the ink that is not scraped by the scraper, which moves to the film during printing, becoming a piece of ink stain. Plate fouling occurs in an atomized and faceted manner. Black ink is prone to this phenomenon

reason:

1) the efficiency of scraping ink is reduced due to the abrasion or poor grinding of the scraper

2) surface damage caused by poor chrome plating quality or wear of the plate

3) impurities and coarse particles in the ink jack up the scraper

4) the adhesion of ink to the plate roller is too strong

solution recognition:

1) reduce the printing speed

2) blow to the non graphic part of the printing ink, so that the ink that has not been scraped can quickly dry and cannot be transferred to the film

3) adjust the position of the scraper to make it more upright on the printing roller

4) replace or regrind the scraper

5) dilute the ink with quick drying diluent to improve the drying speed of the ink

6) reduce the viscosity of the printing brush

7) increase the pressure of the scraper

3. Blocking

in gravure printing. The transfer rate of ink from the eyes is usually about 50 ~ 70%, and about 1/2 ~ 1/3 of ink is always left in the eyes. If the residue rate is kept at a certain level, it is certainly no problem, but during the printing process, when the ink residue rate in the eyes increases for some reason, the ink transfer rate will also decrease. This caused the blocking of plastic gravure printing

after blocking occurs, the printed pattern and text will be blurred, and the printing color will change. In serious cases, printing cannot be carried out. Especially the light version is easy to happen

reason:

(1) the ink is dry and fixed in the layout

although the transfer rate of ink in the gravure roller eye (that is, the proportion transferred to the surface of the printed object) is usually determined by the type of ink, viscosity, printing speed and other factors, no matter which case. After transfer, there is always 1/2 ~ 1/3 of the ink left in the eyes. These residual parts are affected by some factors. After drying (viscosity increase), when the version roller enters the ink tank again, it is difficult to completely dissolve, and the ink transfer rate decreases. Over time, the line becomes shallower and shallower, and the transfer rate becomes lower and lower. Finally, the plate blocking fault is formed. Of course, such blocking fault is related to factors such as ink type, solvent, drying speed, etc., and the structure of the printing machine also has a great influence

(2) mixing impurities

during gravure printing, the printing substrate (film) often generates static electricity due to its high-speed operation. Because static electricity is used for metallurgy to absorb the surrounding dust and substrate, the fixture is an indispensable part of the electronic universal experimental machine. The fixture brings these impurities into the ink according to the chips of different experimental methods

(3) poor plate making quality

the plate making of gravure printing cylinder is made by first etching or engraving the copper surface, then chromium plating, and then grinding. In these processes, the uneven chrome plated surface generated on the inner wall of the ink eye due to corrosion or engraving, as well as the burrs and Ω shaped eyes generated during grinding, also have a certain impact on the transfer rate of the ink. When the situation is serious, it often causes the low transfer rate and becomes the reason for blocking the analysis panel of the bending tester of plexiglass materials

(4) poor dissolution (deterioration)

when the ink deteriorates and the solvent balance changes, the solubility is low, or different inks are mixed, and other bad solvents are misused, which leads to dissolution deterioration, low transfer rate, and direct blocking

(5) chemical changes

with the progress of printing, two liquid ink or reactive ink will gradually produce chemical reactions such as cross connection, which will deteriorate the fluidity, increase the viscosity, and reduce the transfer rate, which may also be one of the reasons for blocking

solution:

(1) in case of plastic gravure blocking, use solvent or special cleaning agent to clean and solve the cause of blocking

(2) adjust the appropriate temperature and humidity, and select the solvent drying speed suitable for the printing speed and printing environment

(3) the distance between the scraper and the embossing roller shall be shortened as far as possible to prevent the hot air leaking from the box from blowing the layout directly

(4) mix and use slow drying solvent to appropriately improve the printing speed and reduce the viscosity of working ink

(5) in case of ink performance defects, replace the ink in time (or contact the ink supplier for solutions), and try to avoid color combinations with significant differences in ink specific gravity

(6) the ink in the ink tank should be stirred frequently to keep the ink in all parts in a flowing state, and new ink should be added or replaced in time to reduce the occurrence of film formation

(7) when it is caused by the quality of the inner wall of the eye in plate making, the plate should be re plated or revised

(8) wipe the trial roll with solvent before or just after startup. During the printing process, try to avoid stopping halfway. When stopping for a long time, be sure to wash the plate first, or immerse the plate roller in the ink for continuous idling

(9) in fresh ink, when the additives and waxes in the ink crystallize out due to temperature difference and other reasons, try to heat the ink (40 ~ 50 ℃) before use to dissolve it

(10) misuse, deterioration and mixing of solvents with heterogeneous inks will significantly affect the re solubility of inks, so regular special dilution solvents should be used. Ink replacement should be carried out after fully cleaning the ink tray and circulating pump

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