Printing and processing of the hottest hose

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Printing and processing of hoses (Part 2)

next, let's talk about the control of printing pressure. We think this trend will be further developed

the adjustment of flexographic printing pressure is another key factor to ensure product quality. The pressure between the embossing roller, plate roller and embossing roller must be readjusted before each product printing. The adjustment of printing pressure requires the accumulation of operators' usual experience and the standardization and unification of operation methods. The adjustment of printing pressure mainly includes two aspects: ⑴ the pressure between the corrugated roller and the plate roller; (2) pressure between plate roller and impression roller

first, we need to adjust the spacing between the three rollers. During printing (when the unit is pressed), the spacing between the embossing roller and the plate roller is basically the same as that between the plate roller and the embossing roller. 0.38mm (thickness of double-sided tape) + 1.70mm (thickness of printing plate) is 2.08mm. On the old unit flexographic press, we choose two 2.05mm thick kraft liners. When the printing unit is pressed, place the Kraft liners at both ends between the two rollers, and manually adjust the spacing between the embossing roller and the plate roller, and between the plate roller and the embossing roller, so as to pull the same resistance of the pickup liners at both ends as the standard. At this time, the spacing is the ideal pressure value in printing, but it is slightly different from the printing pressure used in actual production, so the operator needs to make some fine adjustments in normal production. Now the Gerais equipment introduced by our factory has changed this series of cumbersome steps in design, adopting special spacing positioning holes, and using spacing positioning pins to position the positioning holes, so as to ensure the spacing between the three rollers more accurately. This positioning spacing can also be adjusted appropriately in actual production as required. The pressure during printing is adjusted when each unit is under pressure

before starting production, we first position the spacing of each color deck, and relax the pressure between the plate roller and the embossing roller (pay attention to the synchronization between the operating surface and both ends of the transmission surface). During the slow operation of the flexographic press, start pressing from the first group of printing units, observe whether the ink transfer between the inking roller and the embossing roller is uniform, and then observe whether the ink transfer between the embossing roller and the plate roller is good, and then gradually increase the pressure between the plate roller and the embossing roller until pictures and texts are printed on the composite sheet (pay attention to keep the synchronization between the operating surface and the driving surface, and ensure that the pressure is increased equally at both ends at the same time). Check whether the lines and points printed on the sheet are clear, whether the pattern and text are complete, and whether there are white, false and other problems on the ground. In view of these problems, slightly adjust the pressure between the plate roller and the embossing roller

flexographic printing is a light pressure printing process, and its pressure is far less than that of offset printing and gravure printing. We usually require small pressure when printing with flexography, but when printing with composite hose, because the substrate is composite sheet, we deliberately increase the printing pressure slightly. Taking the field version as an example, it is better to adjust the printing pressure to vaguely see the pressure frame on the edge of the field, so as to avoid the omission of printed pictures and texts caused by the uneven thickness of the composite sheet per unit area

3. In the flexible printing process of hose, the requirements for printing equipment, printing ink and substrate materials

flexible printing uses composite sheet, a material with higher cost, as the substrate, so we have higher requirements for the performance of flexible printing equipment than ordinary flexible printing machines, and the printing equipment must be equipped with corona treatment devices. d) The measurement results and production date of this batch of products. The printing unit must be installed with a full UV drying and curing system, and the equipment needs to have an accurate tension numerical control system and the overall stability of the whole machine. According to the author, although many domestic equipment manufacturers such as Ziguang, Heiniu, beiren Fuji, Xinmin Taiyang, Taihang, etc. produce narrow width flexographic printing machines, the equipment for composite hose printing still relies mainly on imported equipment. In terms of printing quality of composite hose, we need equipment with high overall stability, convenient printing quality control, fast printing speed, high flexibility of product variety replacement and outstanding printing efficiency of the whole machine, so as to ensure the quality of hose products

flexographic printing is a relief printing method, which has been developed for a hundred years. However, the popularity and application of UV ink in domestic flexographic printing has only been a few years. Compared with water-based ink and solvent based ink, UV ink viscosity is relatively high, and it is easy to produce the weakness of poor leveling when printing on the line of hose, resulting in poor ink uniformity of corrugated roller. During operation, it is necessary to increase the pressure between corrugated roller and plate roller to show the hierarchical effect of printing. But this operation often causes the problem of paste, the printing resistance of the line version decreases, and the color saturation of the print is not enough. At present, water-borne UV ink has been developed abroad, but the ink price is relatively expensive. In use, waste is often caused by improper operation. From the perspective of economic interests, we must rely on the strong working spirit of employees and the accumulation of long-term operation experience, and pay attention to daily savings

printing materials are the largest expenditure in hose printing costs. However, in the printing process, there are still coarse and deep wear marks on many waste grinding surfaces, which are caused by the unstable quality of the sheet. The different tightness at both ends of the composite sheet, the wrinkle and rib on the surface, the uneven thickness per unit area, and the large change of the internal friction coefficient are all the reasons for the decline of the yield. Composite hose printing has very high requirements for the printability of composite sheets. We also hope that the manufacturers of composite sheets can further improve its overall quality, stabilize its printability, let users better control the printing quality of hoses, reduce product costs, and achieve the purpose of win-win between suppliers and users

4. Advantages of flexographic printing in composite hose printing

flexographic printing process is no longer a strange printing process in China's printing industry. Its advantages in overall printing quality, printing cost and production cycle have been fully affirmed in the hose industry. Moreover, due to the environmental protection characteristics of flexographic printing, it is more popular with customers, and the production of composite hoses has a relatively sufficient business source. The printing production speed of the flexographic press and the equipment connection production capacity can ensure that customers can receive the required composite hose products quickly and in time. The UV ink used by flexo in hose printing makes the customer's products truly green, safe and reliable. The products can easily open the foreign market and create greater profit space for the customer after the completion of the experiment

5. problems and solutions of hoses in the process of flexographic printing

hoses also have some problems in the process of flexographic printing. Because the outer packaging of hoses adopts lithography, many designers will copy the sample of offset printing and use it in the printing of hoses, and hope to print exactly the same effect with different printing methods and printing processes. This practice will never get satisfactory results. We should tell the designer that when designing the manuscript, we should try to choose large pieces of field or lines, and choose spot colors, so as to give full play to the advantages of flexible plate spot colors, bright and eye-catching, and high saturation. In addition, we should not make clear the front and back chromaticity, and it is best to have a white leak in the middle. The conventional practice is to leak more, not stack more, so as to improve the error of flexible plate overprint in printing

we expect the printing industry to carry out more publicity, introduce the advantages and limitations of flexographic printing process characteristics and performance ability, and cultivate more flexographic professionals. We hope that hose designers can design originals that are more in line with the flexographic printing process and commodity publicity effect, so that flexographic printing can be better applied to hose printing

Author: Li Bo, Li Xiang: Shanghai Changhong (Changfu) hose factory

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