In the daily production process, how to keep the consistency of the label printing color has been a difficult problem for the book printers in china production operators. Many label printing enterprises have been complained or returned due to the color difference of label products. So, how to control the consistency of product color in the process of label production?

Establish a reasonable color management system

We know that it is impossible for printing products to avoid color difference completely. The key to the problem is how to control the color difference within a reasonable range. So, the first step for label printing enterprises to control the color consistency of label products is to establish a sound and reasonable color management system, so that operators can understand the scope of qualified products. There are several points.

1. make sure the upper and lower limits of product color

When we first produce a label product, we should make the upper limit, standard and lower limit of the color of the label product, and then set it as "sample sheet" after the customer confirms. In the future production, the standard color of sample sheet is the basis, and the fluctuation of color cannot exceed the upper and lower limit strictly. In this way, the color consistency of label products can be guaranteed, and a reasonable range of color fluctuation can be given to the production personnel, and the color standard of the product can be more operable.

2. Improve the system of sample signing, inspection and sampling inspection of first and last parts

In order to further ensure the implementation of color standards, the inspection items of label product color should be added to the first and last part sample signing system of label products, so that the production management personnel can control the color difference of label products, and the inappropriate label products shall not be inspected and passed. Meanwhile, inspection and sampling inspection shall be strengthened to ensure that label products beyond the reasonable range of color difference can be found and processed in time during the printing and production of label products.

Printing standard light source is very important

Many many label printing enterprises do not use the printing standard lighting source, which causes hidden trouble to the color consistency control of label products. Many label printing enterprises use lighting source to see the color difference between the night shift and the daylight, which leads to the difference of printing color. Therefore, it is suggested that the majority of label printing enterprises must use the printing standard lighting source to carry out lighting. If necessary, the enterprises with conditions need to equipped with standard light source box, so that employees can compare the color of label products under the standard light source. This can effectively avoid the problem of poor color of printing due to the nonstandard lighting source.

Ink problems can cause color differences

There is such a situation: after label products are placed at the customer for a period of time, their ink color gradually changes (mainly shows fading), but the same phenomenon has not occurred in the previous batch of products. This is usually due to the use of expired ink. The shelf life of ordinary UV ink is usually one year, and it is easy to fade the label products when using expired ink. Therefore, for label printing, the printers in china must pay attention to the use of the ink produced by the regular manufacturers when using UV ink, and pay attention to the quality guarantee period of ink, timely update the inventory, so as to avoid using expired ink. In addition, in the process of printing production, attention should be paid to the use of ink additives. If the ink additives are used too much, it may also lead to the color change of the ink after printing. Therefore, when using various ink additives, it is best to communicate with ink suppliers before determining the correct proportion range of additives.

Color consistency of spot color ink

In the process of label printing, it is often necessary to prepare spot color ink. Many label printing enterprises are far from the sample when preparing the spot color ink. The main reason for this kind of situation is that the ink ratio is not correct. Spot color ink is made up of many primary color inks, and most UV inks are Pantone color system. So we often prepare the spot color ink according to the proportion given on the color card. But here to point out, the color pass color card ink ratio is not necessarily completely accurate, often there will be small differences. At this time, there is a certain requirement for the experience of the china printing staff, because the sensitivity of the printing personnel to the ink color is very important. Printing personnel should learn more and practice, and accumulate experience in this field to reach the level of proficiency. Here, I want to remind you that not all the inks are based on the color pass system. When encountering the ink of non color pass system, the ratio on the color pass color card can not be taken as the standard, otherwise it is difficult to prepare the required color.

In addition, many label printing enterprises have equipped electronic scales to ensure the accuracy of ink proportion. This behavior is worth advocating. Standardization is one of the important measures for the progress of industrial production. The first prepared spot color ink shall be recorded on the process card by the operator, so as to provide data basis for the next time the spot color ink is prepared, and the consistency of the color of the special color ink prepared by different shift and different operators can be guaranteed.

Printing plate making and color consistency

Many label printing enterprises have encountered such situations: when tracing samples, their own printed label products are far from the color of samples provided by customers. Most of these problems are caused by the density and size of dot on the plate and the density and size of dot on the sample are not correct. In this case, I suggest to improve the following steps. First, it is very important to measure the number of mesh wires in the sample with a special net ruler to determine the number of screen wires added to the plate and the number of added wire of the sample. Secondly, the size of the dot on the screen of each color plate and the dot size of the corresponding color of the sample are observed by the magnifying glass. If not, it is necessary to adjust it to the same or approximate size. It should be noted that the dot size set in plate making is slightly smaller than that on the sample because the printed dot will expand. Finally, observe whether the color of printing ink is consistent with the sample ink color. Generally, the above three items can be achieved. The printed label products are basically the same as the customer sample colors, and will not be too different.

The parameters of the screen roller in flexographic printing are related to the color consistency

Some printers in china use flexographic equipment to print labels, such as: when chasing the sample color provided by customers, no matter how can they reach the same or close degree with the sample color, the dot on the printing plate under the magnifying glass finds that its size and density have been very close to the customer samples, and the color phase of ink is similar. So what is the cause of the color difference?

The color of flexographic label products is affected by the ink phase, dot size and density, and also by the number of lines and the depth of the holes of the roller. Generally, the ratio of the number of mesh lines of the roller to the number of screen lines added to the plate is 3:1 or 4:1. Therefore, in order to keep the color close to the sample when printing label products with flexographic equipment, in addition to the size and density of dot in the process of plate making, attention should be paid to the number of reticle roller mesh lines and the depth of mesh holes. By adjusting these parameters, the effect of the color proximity between the label product and the sample can be achieved. Of course, flexographic printing has its own advantages in color consistency control, that is, its short ink path and metering ink feeding mode. Once these parameters are determined, the same label colors of each batch produced in the future will be basically the same.