In the daily production process, how to maintain the consistency of label printing color has always been a problem that puzzles production operators. Many label printing enterprises have been complained by customers or even returned goods because of the color difference of label products. So, how to control the consistency of product color in the label production process? The author discusses with you from the following aspects.
(1) Establish a reasonable color management system
We know that it is impossible for prints to completely avoid chromatic aberration. The key issue is how to control the chromatic aberration within a reasonable range. Then, the first step for label printing companies to control the color consistency of label products is to establish a perfect and reasonable color management system to let operators understand the scope of qualified products. The specific points are as follows.
1. Clarify the upper and lower limits of product color
When we first produce a label product, we should work out the upper limit, standard and lower limit of the color of the label product, which will be determined as "sample" after confirmation by the customer. In the future production, based on the standard colors of the proofs, and strictly stipulate that the color fluctuations cannot exceed the upper and lower limits, so that while ensuring the color consistency of the label product, it can also give the production personnel a reasonable color fluctuation range and also make the product The color standard is more operable.
2. Improve the system of signing, patrol inspection and random inspection of first and last parts
In order to further ensure the implementation of color standards, the inspection items of the label product color should also be added to the labeling system of the first and last parts of the label product, so as to facilitate the production management personnel to control the color difference of the label product. . At the same time, strengthen inspection and random inspection to ensure that label products that exceed the reasonable range of color difference can be discovered and processed in a timely manner during the printing process of label products.
(2) Printing standard light source is very important
According to the author's understanding, many label printing companies currently do not use printing standard lighting sources, which poses hidden dangers to the color consistency control of label products. Many label printing companies use the illumination light source to see the color when they are working at night, which is very different from the color seen in the daytime, which leads to the difference in printing color. Therefore, it is recommended that the majority of label printing enterprises must use standard printing light sources for lighting. Qualified enterprises also need to be equipped with standard light source boxes to allow employees to compare the color of label products under the standard light sources. This can effectively avoid the problem of chromatic aberration of printed products caused by non-standard illumination light sources.
(3) Ink problems will cause color difference
The author has also encountered such a situation: after the label product is placed at the customer for a period of time, the ink color gradually changes (mainly manifested as fading), but the same phenomenon has not occurred in the previous batches of products. This situation is generally caused by the use of expired ink. The shelf life of ordinary UV inks is usually one year, and the use of expired inks is prone to discoloration of label products. Therefore, label printing enterprises must pay attention to the use of inks produced by regular manufacturers when using UV inks. At the same time, they should pay attention to the shelf life of inks and update their inventory in time to avoid the use of expired inks. In addition, pay attention to the amount of ink additives used in the printing process. If the ink additives are used excessively, it may also cause changes in the color of the ink after printing. Therefore, when using various ink additives, it is best to communicate with the ink supplier before determining the correct proportion of additives.
(4) Color consistency of spot color inks
In the process of label printing, it is often necessary to prepare spot color inks. Many label printing companies have a far cry from the color of samples when preparing spot color inks. The main reason for this kind of situation is the wrong ink ratio. Spot color inks are prepared from a variety of primary color inks, and most UV inks are PANTONE color systems, so when we formulate spot color inks, we often formulate them in the proportions given on the Pantone color card. However, it should be pointed out that the ink ratio on the Pantone color card is not necessarily completely accurate, and there will often be slight differences. At this time, there are certain requirements for the experience of the printing staff, because the printing staff's sensitivity to the ink color is very important. Printing staff should learn more and practice more, and continue to accumulate experience in this area to reach the level of proficiency. Here I want to remind you that not all inks are based on the Pantone color system. When you encounter non-Pantone color inks, you cannot use the ratio on the Pantone color card, otherwise it will be difficult to formulate the required s color.
In addition, at present, many label printing companies are equipped with electronic scales to ensure the accuracy of the ink ratio. This behavior is worth advocating. Standardization is one of the important measures for industrial production progress. The spot color inks prepared for the first time should be recorded on the process card by the operator in order to provide a data basis for the next time the spot color ink is formulated, and at the same time ensure that different shifts and different operators prepare spot color inks Color consistency.
(5) Pre-press plate making and color consistency
Many label printing enterprises have encountered such a situation: the color of the label products printed by themselves when the sample is followed is very different from the color of the sample provided by the customer. Most of these problems are caused by the unequal density and size of dots on the printing plate and the density and size of dots on the sample. In such cases, the author recommends the following steps to improve. First of all, it is very important to measure the number of screen lines of the sample with a special screen ruler to confirm that the number of screen lines of the printing plate is consistent with the number of screen lines of the sample. Secondly, observe through a magnifying glass whether the dot size of each color printing plate is consistent with the dot size of the corresponding color of the sample. If they are inconsistent, they need to be adjusted to a uniform or approximate size. It should be noted here that since the dots after printing will expand, the dot size set during plate making is slightly smaller than the dots on the sample. Finally, observe whether the hue of the printing ink matches the hue of the sample ink. Under normal circumstances, the above three items can be achieved. The color of the printed label product and the customer's sample are basically the same, and will not be too different.
(6) The parameters of the anilox roller in flexo printing are related to color consistency
Many label printing companies have used flexible printing equipment to print labels. Such a situation has occurred: when chasing the color of the sample provided by the customer, it can not reach the degree of consistency or close to the color of the sample no matter what. Its size and density are very close to the customer's sample, and the hue of the ink is similar. So what is the cause of the color difference?
In addition to the influence of ink hue, dot size and density, the color of flexographic label products is also affected by the number of anilox rollers and the depth of the holes. In general, the ratio of the number of screen lines of the anilox roller to the number of screen lines of the printing plate is 3: 1 or 4: 1. Therefore, when printing label products using flexo printing equipment, in order to keep the color close to the sample, in addition to the size and density of the dots as much as possible in the sample making process, also pay attention to the number of anilox roller mesh lines and the depth of the mesh holes ï¼Œ Adjust these parameters to achieve the effect that the color of the label product is close to the sample. Of course, flexo printing also has a unique advantage in terms of color consistency control, that is, its short ink path and metered ink feeding method. Once these parameters are determined, the color of similar labels for each batch of future production will be basically consistent.
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