The most complete analysis of the problems encountered in replacing ink during the White Paper Gift Boxes printing process

The most complete analysis of the problems encountered in replacing ink during the White Paper Gift Boxes printing process

Many plastic color printing factories sometimes need to replace ink manufacturers due to ink quality problems, cost, stability and other reasons, but they are more cautious about such problems, for fear that the replacement of ink will affect production and cause reciprocating fluctuations in product quality. cause economic losses. The ink properties of different manufacturers will be different, and will have different effects on printing.

There are many types of inks currently used in the plastic color printing industry. They are divided into surface printing inks and inner printing inks according to different printing positions. Liyin ink is divided into polyester nylon ink, OPP special ink, aluminum foil special ink according to different printing materials; according to different use temperature, it is divided into ordinary ink, boiled ink, cooking ink, etc.

Many plastic color printing factories sometimes need to replace ink manufacturers due to ink quality problems, cost, stability and other reasons, but they are more cautious about such problems, for fear that the replacement of ink will affect production and cause reciprocating fluctuations in product quality. cause economic losses. The ink properties of different manufacturers will be different, and will have different effects on printing.

Common problems that may be encountered in replacing ink

1. Hue of ink: Ink is divided into primary color ink and spot color ink. The primary color inks produced by ink manufacturers are all the same, namely original red, original yellow, original blue, black, white, etc; Some spot color inks (generally for large print volumes and special patterns).

2. Viscosity of ink: The viscosity of ink produced by different ink manufacturers will be slightly different. After the color printing factory dilutes the ink with a mixed solvent, the viscosity of the ink during printing is generally controlled between 16-26 seconds (No. 3 Chaanthracene Cup) . Because the printing color sequence and the nature of the ink itself are different, the viscosity required for each ink will also be different. Generally, the viscosity of white ink is the lowest, about 17 seconds; the viscosity of black ink is the highest, about 25 seconds, and other colors. Ink is somewhere in between.

3. The fineness of the ink: The fineness of the same type of ink is generally roughly the same between different ink manufacturers, but the difference between the ink manufacturers is that the normal distribution of the ink particles is different, and of course there are other aspects. Differences, for example, are as follows: the particle size of the ink produced by factory A and the ink produced by factory B is between 20 and 28 microns, but the particle size distribution of the ink produced by factory A is more concentrated around 24 microns, while the ink produced by factory B is about 24 microns. The distribution between 20 and 28 microns is relatively dispersed, so the printing suitability of the ink of factory A is better than that of factory B (as shown in Figure A).

4. In addition to the performance of these inks, it should be noted that for the plastic color printing industry, there is also a performance requirement, that is, the release of residual organic solvents in the ink, because the products from the color printing factory are generally in direct contact with food, although the ink Substances such as glue are not in direct contact with food, but some of the small molecular substances will still migrate to the surface of the film, affecting the hygiene of food. Therefore, there are corresponding national standards for residual solvent countries, and color printing factories should also purchase corresponding testing equipment. , but the current situation is that most small factories do not have such equipment, and many domestic color printing factories with complete testing equipment do not strictly control this indicator, resulting in unsatisfactory product hygiene indicators.

5. The production process is also a factor to be considered, but at present the technology level of each color printing factory is basically mature, and the difference is not big, but special attention should be paid to the difference in the speed of the printing machine. The printing speed between different color printing factories is about 80~250 meters. /min, if the color printing factory wants to replace the ink, the viscosity characteristics of the ink should be considered, especially the ink viscosity of ultra-high-speed printing (above 200 m/min) should be very low, and the color density should be up to the standard, and the ink factory has high requirements. .

Hue problems often encountered by ink color printing manufacturers

1. There is a color difference between the inks of the same hue produced by different ink manufacturers (as shown in Figure B). From the figure, we can see that there is a certain difference in the hue between the inks of factories A and B, and there is no difference in the printing pattern. When the color inks are superimposed, the color difference may not feel large, but if there are overlapping parts, the difference may be obvious. This requires the ink factory to make appropriate adjustments to the ink formulation to minimize this difference. It adds cost to the color printing factory, so it should also be taken into account when changing the ink manufacturer.

2. General products will have the superposition of different color inks due to screening, and there will be slight differences in hue if the version is not revised and the process conditions remain unchanged. At the same time, due to the characteristics of color printing, most of the printing colors are more than 5 colors, and more than a dozen colors. In addition to the primary color ink, there are also spot color inks. In addition, other auxiliary printing materials, such as varnish, must be added according to special process requirements. Wait. Therefore, the application of spot color inks in color printing factories is also very common. Spot color inks are generally specially adjusted by the technicians of color printing factories. Under the condition that the printing plates and other process conditions remain unchanged, the replaced inks can generally be used. The color sample of the product that is close to the original ink proofing, but if the printing pattern is complex and the process is special, it will often fail to meet the requirements of the color sample. If this is the case, the ink factory needs to adjust the ink formula or revise the version. If it is the latter, then It will increase the cost for the color printing factory, so this should also be considered when changing the ink manufacturer.

The general process of changing the ink (from the ink of factory A to the ink of factory B)

(1) First, provide the color samples of primary color ink and spot color ink to the ink of factory B and factory A. If it is a printed matter, it is required to be a solid color block without superimposition.

(2) The color printing factory has multiple sets of plates, first provide one or several sets of plates to the ink factory, and ask factory B to proof. Generally, the selection of the version provided to the B factory is generally based on primary color ink sticks and commonly used spot color inks.

(3) Entering the experimental stage, the technicians of the ink factory (proficient in printing technology and the performance of the ink) usually come to the site for debugging.

(4) In this process, there are mainly several primary color inks. The commonly used spot color inks basically meet the hue requirements of the inks of factory A, so the color printing factory can basically replace the inks of factory B.

(5) But this does not mean that color printing factories can sit back and relax. Color printing factories generally have more difficult versions (more spot color inks), and ink factories generally produce spot color inks, so the difficulty lies in the production of such products. , The printing sample and the standard sample produce color difference. When the primary color ink is basically the same, the color difference is generally caused by the spot color ink. The specific analysis is as follows:

a. In the printing pattern, when the spot color ink is not screened or overlapped, the color difference of the spot color ink occurs, and the ink formula is generally adjusted by the ink factory. If the spot color ink is prepared by an ink factory, it is generally one of the spot color inks prepared by the ink factory (a spot color ink is prepared from several inks).

b. In the case where the printing pattern is screened and the inks of different hues are superimposed at the same time, it should be analyzed first whether it is caused by the primary color ink or the spot color ink, and should be adjusted according to E1. If it is caused by primary color ink, the ink factory should be asked to adjust the formula of primary color ink. If it is caused by spot color ink, it should be adjusted according to E1.

c. There is also a more special and complicated situation, that is, there are multiple hues superimposed in the pattern of a product, that is, the same plate has several pattern stacking ports. If the proofing is for the first time, the proofing result is inconsistent with the standard sample. Among them, some of the printing samples are consistent, and the other parts are inconsistent, so pay attention to the analysis:

1. There are differences in the hue of primary color inks between different ink manufacturers.

2. There are differences in chromaticity between the same color ink (sometimes can be solved by revision).

The above briefly discusses the problems that color printing manufacturers often encounter when replacing ink. I hope it will be helpful to relevant manufacturers. I hope to discuss related issues with you.

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