Control the fineness of flexographic products during printing

In recent years, with the application of CDI technology in the flexo printing industry, flexo printing products have got rid of the image of low early printing quality and poor precision, and gradually hit the mid-range and high-end markets. Today, many flexo manufacturers have been able to produce exquisite products that compete with traditional offset gravure. The scope of application of the product has also been extended from the early low-grade packaging bags, carton corrugated paper, etc. to tobacco labels, wine labels, high-fidelity packaging, films, fine corrugated paper, and milk packages. But simply having a digital flexo does not mean that you have all the high-precision flexo quality. Many manufacturers reflected: "We have used a high-quality digital flexo, but the product fineness has not achieved the desired results." One of the reasons is to ignore the control of the fineness of the product in the printing process, or to ignore certain details in the printing. In response to this problem, I will talk about my personal experience with the company's production.

First, the impact of the substrate on the finesse of the product.

First, the substrate has a great influence on the fineness of the product. Especially for coated papers with a basis weight of 90g/m2 or less, they are transported over long distances and piled up for a long time. The water content of the coated paper varies greatly depending on the surrounding environment. In addition, the flexo printing machine has a paper path length and must be dried by a multi-color machine. The thin paper is deformed many times and the deformation direction is inconsistent. These conditions have a great influence on the quality of multi-color overprint products. Therefore, paper suppliers are required to strictly control the water content at the factory, shorten the transport cycle as much as possible, and avoid exposure during transportation or staying in rainy weather. These measures are prerequisites for the printing industry to control the fineness of products during the printing process. . At the same time, it is recommended that printing manufacturers pay attention to the temperature and humidity of the warehouse in the storage process should be consistent with the temperature and humidity of the printing environment.

Second, the printing process of ink adjustment directly affects the fineness of flexographic products

Fine prints usually meet the following quality requirements:
(1) The ground is smooth and delicate, with neat surroundings and no ghosting.
(2) Part of the network cable satisfies: clear, small deformation, and distinct layers.
(3) Fine lines and small texts require clear lines, fine text, and no paste.
(4) Multi-color printing requires accurate overprinting, no leaks, and no overlapping frames.
So, under the premise that the printing pressure has been adjusted in place, only by adjusting the ink properties to maintain a stable viscosity and good printability, the printed matter can meet the above four requirements.
For example: (1) In general, the field product uses an ink with a viscosity of 45' to 60' (Paint 4# cup), and the ink leveling and hiding power of the viscosity range are both. Ink coverage is good, solid level; ink leveling is good, the field is delicate and shiny. Otherwise, the viscosity of the ink is too large, the ink transfer ability is poor, and the printing on the ground is not true; the viscosity is too small and there are water marks on the ground. (2) The viscosity of the ink used in the cable products is 30'-40'(paint #4 cup), the ink transfer performance of the viscosity range is good, and the reproduction performance of the dot is strong. The printed product dot is clear, the deformation is small, and it is not easy to paste Edition, dirty version. (3) Multi-color overprint products should be designed to minimize the trapping parameters under the premise of satisfying trapping, and the printing color sequence should be reasonably arranged to ensure that the ink color of the latter color can cover the trapping of the previous color. .

Third, the setting of the printing process has a crucial influence on the fineness of the product during the printing process.
Printing process settings: such as the trapping parameter settings, the printing sequence before and after the arrangement, there is pressure convex, hot foil can not be connected to the post-process set the mark.

The company once had a product that was darkly overprinted on the ground twice, with many small anti-white characters on it. We design according to the normal trapping parameters, and the results are not clear and imperfect. Later, in practice, we worked out the rules, set them according to “anti-trapping”, and arranged printing sequences suitable for the trapping parameters so that the anti-white characters would be printed beautifully, and it would be almost impossible to see the two-color overprint. effect.

Compared with offset printing and gravure printing, the flexographic printing press has poor overlay accuracy. If the products printed by the printing factory must be processed through subsequent processes such as bronzing and embossing, and they cannot be completed online with the flexo press at the moment, then the simple and easy-to-read mark on the plates is to ensure that the subsequent processes are gilded. The exact premise of die-cutting. This is a very small job in the printing process setting, but it is the key to ensure the exquisiteness of the product after the packaging is formed, and whether the product printing is suitable and perfect after the packaging is used is an important aspect reflecting the fineness of the product.

In short, the improvement of the fineness of flexographic products, in addition to being directly related to the printing equipment and the printing plate production, has a direct bearing on the selection of the substrates, the ink adjustment, the printing process, and the printing operation level during the printing process. Closer relationship. It can be said: "Who owns these software technology talents, who will control the fineness of the flexographic products in the printing process, and who will truly have high-quality flexographic quality?"

Author: Ping Baoping good cat Group Baoji Accor Printing Co., Ltd.

Reprinted from: Chinese Flexo