What should be paid attention to when using corrugated cardboard for flexographic printing (below)
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8. When the corrugated board is printed with flexographic printing, the side of the printing plate is too ink-stained, and the ink spots appear on the imprint. The dots and small characters are particularly noticeable.
When the corrugated board is flexographically printed, the side of the printing plate has too much ink on the side, and the ink spots appear on the imprint. The dots and small characters are particularly prominent due to various reasons. We will have the ink on the side of the printing plate for different reasons. More, there are ink spots on the imprint, especially the dots and small characters, and the corresponding solutions are as follows:
(1) Due to foreign matter in the ink, the ink on the side of the printing plate is too much ink, and the ink spots appear on the print. The dots and small characters are particularly noticeable. The solution is to filter the ink.
(2) Due to the inappropriate use of text, patterns and the number of screen lines, the ink on the side of the printing plate is too much ink, the ink spots appear on the print, and the dots and small characters are particularly noticeable. The solution is to improve the design.
(3) Due to the improper pressure of the ink fountain roller, the ink on the side of the printing plate is too much ink, and the ink spots appear on the print, especially the dots and small characters. The solution is: reasonable pressure regulation.
(4) Due to the improper pressure between the anilox roller and the printing plate, printing plate and substrate, the ink on the side of the printing plate is too much ink, and the ink spots appear on the print, especially the dots and small characters. The solution is to re-adjust the pressure.
(5) Due to the ink string of other units on the printing plate, the side of the printing plate has too much ink on the side of the printing plate, and the ink spots appear on the printing mark, especially the dots and small characters. The solution is to adjust the dry state and solvent between the various color groups.
(6) Due to the high viscosity of the ink, the ink on the side of the printing plate is too much ink, and the ink spots appear on the print. The dots and small characters are particularly noticeable. The solution is to adjust the ink viscosity.
(7) Due to the internal friction of the ink, the ink on the side of the printing plate is too much ink, and the ink spots appear on the print. The dots and small characters are particularly noticeable. The solution is to use a suitable defoamer.
9 During the flexographic printing process, phantoms appear
In the printing process, there is often a cloud-like obscurity on the printed matter. The reason for this phenomenon is that the uniform ink is poor; the amount of ink is small, the ink flowability is poor; the anilox roller is unclean.
The solution is to replace the ink roller and the anilox roller to make the diameter different; increase the ink supply; improve the ink flow; clean the anilox roller.
10 In the process of flexographic printing, ink drying occurs
During the printing process, the phenomenon of ink drying on the ink roller or printing plate of the ink transfer system often occurs. The reason for this phenomenon is that the solvent evaporates too quickly; the ink fountain cap is not covered; in the stencil, the ink has dried on the printing plate.
The solution is to use a solvent that is slow to volatilize; cover the ink fountain lid and clean the plate.
11 In the process of flexographic printing, small characters are unclear
In the printing process, small characters and fine dots are often unclear. The reason for this phenomenon is that the printing plate is too hard, the definition is not good; the ink is poor; the solvent formulation is improper; the printing operation is not correct.
The solution is to re-print the plate, replace the ink; adjust the solvent formulation; pay attention to the correct operation.
12 corrugated cardboard with flexographic printing, ink blistering
When the corrugated board is printed by flexographic printing, the foaming of the ink is caused by various reasons. We will introduce the foaming of the ink for different reasons and the corresponding solutions are as follows:
(1) The ink is foamed due to the equal speed of the ink fountain roller and the anilox roller at high speed. The solution is to reduce the speed ratio of the two.
(2) The ink is foaming due to excessive fluctuations in the ink circulation. The solution is to check the oil pump impeller and gears.
(3) Foaming due to improper use of solvents. The solution is to choose the right solvent.
13 Ink viscosity is unstable during flexographic printing
In the printing process, the phenomenon that the viscosity of the ink increases during the printing process often occurs. The reason for this phenomenon is that the thixotropy of the ink is poor; the solvent component is volatilized; and the ink is foamed.
The solution is to measure the thixotropy after the ink is circulated, add a special solvent to adjust the ink, and add defoaming agent to the ink to defoam.
14 During the flexographic printing process, the printed matter does not wear off
In the printing process, the phenomenon that the ink film peels off after rubbing of the printed matter often occurs. The reason for this phenomenon is that the ink is too thin; the ink has poor adhesion, the binder fails, and the surface of the ink film is too dry.
The solution is: thickening the ink, changing the ink with good adhesion; adding a wax-based slip agent; and printing a protective varnish on the surface of the printed matter.
15 How to effectively handle flexo overprinting
At present, the corrugated carton packaging market is highly competitive, raw material prices are high, and carton production tends to be meager. The printing requirements of customers have evolved from traditional monochrome printing to multi-color printing, and even to layer printing, and printing requirements are getting higher and higher. Although flexible printing is flexible and efficient, the price of matching accessories is relatively high. The price of ink is about 20 yuan/kg, and the flexible plate is about 0.15~0.4 yuan/cm2. In this way, the cost of 1kg of ink and one printing plate is equivalent to the profit of hundreds of thousands of qualified cartons. Therefore, carton companies must start from saving 1kg of ink and reducing the number of flexible plates per 1 square centimeter.
Handling the overprinting process in the flexible plate can save the carton company a lot of cost. Because the waste caused by overprinting often accounts for a large proportion of all waste products, and the waste caused by flexographic printing is difficult to use, the waste caused by overprinting is not allowed, and it is derived from trial and error in the school edition. Therefore, in order to reduce the scrap rate and improve the printing efficiency of enterprises, it is necessary to start from solving the problem of overprinting and shorten the time of school printing. At the same time, the reduction of waste reduces the waste of other excipients, which reduces the waste of ink. The flexo plate is more expensive, but can be made into a loose version to reduce costs. The cost of the plate is about 20% less than the full version, which greatly reduces the processing cost.
The method of splicing the stencil can use the method of offsetting the color of the offset printing machine. This method largely eliminates the double-sided adhesive which can only rely on the base drawing or the manual stroke method for imposition, low accuracy and repeated correction. The viscosity is reduced, the plate is deformed, and the defects of the plate are up and dirty during the printing process.
16 Ink gelation occurs during flexographic printing
In the printing process, the viscosity of the printing ink often increases, the stirring does not flow, and the gel appears as a paste. The reason for this phenomenon is that the printing ink is too viscous; the wrong solvent is used; the storage is improper; the ink deteriorates over time.
The solution is to reduce the ink viscosity; use a special solvent, the ink is sealed and stored, and the ink is replaced.
17 Ink whitening occurs during flexographic printing
It is inevitable that various faults occur during the flexographic printing process, and the causes are also very complicated. Therefore, through in-depth analysis, we should grasp the law of failure, and continue to accumulate practical experience and solve it correctly.
In the printing process, the ink is partially gelatinized, and the ink film absorbs whitening after the solvent is volatilized. The reason for this phenomenon is that the solvent volatilizes greatly; the humidity is too high; the resin precipitates.
The solution is to change the solvent composition, reduce the humidity, change the mixing solvent ratio, and add butanol.
The above problem-solving method is crucial to the quality of corrugated box flexographic printing in the actual production of the enterprise.