Printing color difference control method
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In the daily printing production process, how to maintain the consistency of printing color has always been a problem that plagues the printing production staff. Many printing companies have also experienced serious quality accidents due to the color difference of printed products, customer complaints and even returns. To this end, this article will explore how to control the consistency of product color during the printing process.
Establish a sound color management system
It is well known that it is impossible to completely avoid chromatic aberration in the printing process. The key is how to control the chromatic aberration within a reasonable range. The first step in the printing process to control the color consistency of the product is to establish a perfect color management system, so that the operator can understand the standards of qualified products, including the following two points.
1. Determine the upper and lower limits of the product color with the customer
When we first produce a product, we should set the standard upper and lower limits of the color of the product, and set it as “standard proof” after the customer seals the sample. In the future production, the standard color of the standard proofs (which may also be the first batch of product samples) is based, and the fluctuation of the color is strictly not allowed to exceed the upper and lower limits of the standard. In other words, confirm the color difference standard range with the customer in advance, and ensure a reasonable color fluctuation range for the production personnel while ensuring the color consistency of the product, so that the product color standard is more operable. Do not catch up with the batch sample every time you produce it. This will lead to more batches of printing, the more the color difference of the product, the difference is a thousand miles.
In addition, it must be noted that the “standard proofs” of the customer's seals should be replaced periodically to avoid deviations between the standard proofs and the actual printed products due to the long time.
2. Improve the first and last item signing, inspection and sampling system
If you want to further ensure the implementation of color standards, you should also include the inspection items of product color in the "Product Inspection System" and "Inspection Quality Record", so that workshop managers can control the color difference of products, and the inappropriate products are not determined. Passed. At the same time, workshop management personnel and operators should also strengthen inspection and sampling to ensure that products beyond the reasonable range of color difference can be discovered and processed in time during the production process.
With the development of printing inspection technology, the accuracy of the color difference detection equipment has been greatly improved. Conditional printing companies can introduce relevant color difference control devices to achieve digital color difference management.
Equipped with a printed standard light source
Some printing companies do not use printed standard light sources, which brings hidden dangers to the color consistency control of printed products. The color of the product seen under the illumination source during night shifts is very different from the color of the product seen in daylight during day shifts, which may easily lead to differences in printing colors. Therefore, it is recommended that the printing shop must use a standard light source for illumination and, if necessary, a standard light source box.
Guarantee the quality of printing ink
Printing companies sometimes encounter situations where the color of the ink gradually changes after the product has been placed at the customer for a period of time, but the same phenomenon has not occurred in the first few batches of printed products. This is generally due to the use of expired inks. Ordinary inks usually have a shelf life of one year, and the use of expired inks is prone to fading of printed products. Therefore, when using ink, we must pay attention to the ink shelf life, adhere to the principle of first-in, first-out. In addition, in the printing production process, attention should also be paid to the amount of ink additive used. If the ink additive is used in excess, it may also cause a change in the color of the ink after printing. Therefore, when using various ink additives, it is best to communicate with the ink supplier to determine the correct range of additives to be added.
Pay attention to the ratio and information transmission of spot color inks
In the printing production process, it is often necessary to prepare a spot color ink, and in the printing workshop, the color of the ink is often far from the color of the sample. The main reason for this is that the ink ratio is wrong. The spot color ink is made up of a variety of primary color inks, and most of the primary color inks are Pantone color systems, so we usually formulate the spot color inks according to the ratio 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 are often minor differences. This has certain requirements for the operator's experience, requiring it to have a high sensitivity to the color of the ink, requiring it to learn more and more, continuously accumulate experience in spot color ink configuration, improve color sensitivity, and achieve a level of proficiency in ink configuration. . Here I would like to remind everyone that not all of the primary inks are based on the Pantone color system. When encountering the non-Pantong color primary color ink, the ink ratio on the Pantone color card cannot be used. Otherwise, it is very It is difficult to formulate the required ink color.
In addition, many printing companies are equipped with electronic scales to ensure the accuracy of the spot color ink ratio, which is worth promoting (note that the electronic scale should be calibrated regularly). Standardization is one of the important measures for industrial production progress. Our approach is to record the ink ratio on the process card and Quality Record by the operator when formulating the spot color ink for the first time, so as to provide the basic data for the next time the spot color ink is reconstituted, while still ensuring different The consistency of the color of the spot color ink prepared by the shift and different operators.
Make the right plate
We often encounter situations where the color of the product printed during the sample is far removed from the color of the sample provided by the customer. Most of the cases are caused by the density and size of the dots on the plate and the density and size of the dots on the sample. It is recommended to improve according to the following steps.
First, the number of sample screen lines is measured with a dedicated wire ruler to determine that the number of screen-added lines is the same as the number of sample screen lines. This step is crucial.
Secondly, it is necessary to observe whether the size of the dot color of each color plate is the same as the size of the dot corresponding to the color of the sample through a magnifying glass. If it is inconsistent, it needs to be adjusted to be consistent or approximate. It should be noted that since the dots after printing will increase, the dot size set during plate making is slightly smaller than the dot on the sample.
Finally, it is observed whether the hue of the printing ink is consistent with the color of the ink for the sample.
Under normal circumstances, the above three points can be achieved, the color of the printed product and the color of the customer sample can be basically the same, and the difference will not be too large.
Fully evaluate the impact of surface treatment processes on the color of printed products
In the printing process, this situation is often encountered: when printing, the color of the printed product and the color of the sample are very similar, but the color changes greatly after the film is coated, especially after the surface is covered with the matte film, the color difference is greater. This situation must not be taken care of, especially when printing the dark blue series and red and yellow series colors, it is best to do the laminating test before the official production, adjust the printing color according to the post-filming effect, and save the uncoated film. Facilitate subsequent production comparisons. In addition, the calendering process also has a great influence on the dark blue series of color blocks, which must be considered in advance when printing.
Master the color change law after drying in special colors
The printing colors are ever-changing. Some colors are very close to the color of the sample when they are first printed, but they are very different from the sample color after drying, especially when printing with dark blue ink formulated with ink such as luminescent blue. The situation is obvious, you must pay attention when printing.
In addition, metallic inks such as gold and silver, due to the composition of the ink, are monochromatic or spotted inks formulated with them, and will change after drying. At the same time, the color effect of printed products is greatly affected by the observation angle. Therefore, when printing with this kind of ink, it is necessary to know the customer's observation environment in advance, whether it is in daylight or under the light, and try to be consistent.
The printing process is a dynamic balancing process that causes chromatic aberration each time it is turned off. Therefore, the unification of printing colors has become an important printing quality indicator. Many of these tips are long-term experiences in the printing process. I hope that the above ideas will help the industry peers to better control the printing colors and print more personalized and attractive products.