Process quality control of flexographic printing o

2022-09-23
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Quality control of plastic film flexographic printing process

ink

flexographic ink used in plastic film is available at home and abroad. High grade inks are still good at foreign inks at present. The flexo printing ink of the 1980s is suitable for primary flexo printing machines (such as laminated flexo printing machines) to print plastic vest bags (also known as horse bags). In the 1990s, great progress has been made in the flexographic printing process of plastic film. Flexographic inks suitable for high-speed, fine, high-color and strong have rushed to the domestic market. Ink quality control, in addition to the perceived fineness, color viscosity and other parameters, the author believes that the color concentration should be emphasized

flexographic ink. When printing fine flexographic plates, due to the use of high-speed corrugated rollers, even though the current manufacturing process of corrugated rollers has been greatly reformed, the CO2 laser engraving process has been replaced by YAG or other unnamed lasers. For the equipment used in the experimental process, the ink volume has been significantly improved, but the high-speed corrugated rollers also need to rely on high-color ink, which is still an indisputable fact. Many ink companies in their production series, in addition to general products, also provide their inks, or high color density inks, specifically to deal with this situation. However, if the ink in normal production is added too much, exceeding a certain proportion, the resin in the ink is less, and the adhesion between the ink and plastic film will inevitably be reduced. Therefore, the more the ink, the better. According to the preliminary statistics of the lithium branch of China Nonferrous Metals Industry Association, it is also necessary to control a certain degree

the author believes that it is essential to select and control the color intensity of flexographic ink in process quality control. We think it is simple and effective to measure the field density with a densimeter. However, there is still a difference between the ink sample scraped on the film with a scraper and the print sample under the actual printing process conditions (such as a certain number of lines of corrugated rollers, a certain density of double-sided tape, a certain printing speed). This difference should also be noted when using a densitometer for identification. In addition, when it comes to the solvent residue of printing products, we should also pay attention to the selection of resins used in flexo printing inks. Polyamide, nitrocellulose and PVB have their own advantages, which can not be ignored. Foreign produced ink suitable for plastic printing has also been trying to control the domestic market. The author has tested this kind of ink and its performance is good, but there are still some problems. It is estimated that it will take some time to completely replace alcohol ink

draft making and plate making

generally, printing enterprises do not make drafts themselves. The sales department hands over the electronic documents submitted by the customers to the technical department and then transfers them to the special plate making company, which will deal with them. However, we often encounter a puzzling problem, that is, the printing plates produced by the plate making company according to the design in the electronic documents are always unsatisfactory and sometimes have to be reworked

there was once a case that when Coca Cola produced 350ml six cans of shrink packaging, the printing plate made by the plate making company according to the design in the electronic document was sent to Hong Kong for confirmation after the printing was completed. It was rejected twice in succession and returned to work again, because the delivered palm could not reach the approval of the advertising creative department. The customer is not sure. What is the problem? After repeated analysis, we found the reason. Because the heat shrinkable PE film we use has poor transparency and is gray. The whole feeling is that the product is printed on it. In 2000, fanda's design draft was orange red, emphasizing lightness and enthusiasm, but now the products feel a gap

generally speaking, the plate making company needs to make certain adjustments to the electronic documents handed over by the printing enterprises, but this adjustment is mainly based on the adjustment of the point expansion compensation curve and the compensation of the plate extension caused by the curvature radius of the plate. For other parameters, they are generally determined by the parameters in the electronic documents, and at most, in terms of the buckle, it is only to put forward some suggestions from the plate making company. However, in the actual printing process, there are various problems, such as buckle, which can be made by 0.1mm according to the printing process of the satellite flexographic press. But if it is not plastic packaging, but paper trademarks, at this time dozens of trademarks are assembled into a plate, and there is no difference between the main part and the secondary part. For the trademark, it is the main part everywhere, so the 0.1mm buckle cannot take into account the overprint accuracy of the whole layout. In the past, when the author produced the tiger beer aluminum spray paper trademark, he had to put forward a series of specific requirements for the plate making company according to the characteristics of his company's equipment. In some places, the buckle should reach 0.25mm, in some places, it should be empty, and it must not be folded. The same is true for the shrinkage of PE film in the printing process. PE film, especially 25 ~ 40 m PE, shrinks very much in the printing process, and some products reach 3 ~ 4%. In this way, the compensation for the design manuscript is essential

this parameter is unknown to the plate making company, which requires the technical department to put forward its own compensation requirements when submitting electronic documents. In addition, the adjustment of the layout suitable for flexographic printing process, such as the change of gradient curve, large-area field plate making separately from fine lines, must also be taken into account. In this way, the product quality is greatly guaranteed, and the delivery date will not be delayed

therefore, the process quality control of manuscript making is to understand the design in electronic documents and adjust it according to the actual production situation. What we hand over to the plate making company is not only an electronic document, but also a complete set of instructions. If you are at a loss for a moment, you should discuss with the technicians of the plate making company to make a better plan. We feel that the role of the technical department should not be just a setter, but a headquarters

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