The hottest perspective composite hose flexographi

Perspective composite hose flexographic printing (II)

2 Control of printing pressure

the adjustment of printing pressure is another key factor to ensure product quality. Before each printing, the pressure between the embossing roller, plate roller and embossing roller must be readjusted. The adjustment of printing pressure mainly includes two aspects: one is the pressure between the wrinkle roller and the plate roller; The second is the pressure between the plate roller and the impression roller

first of all, adjust the spacing between the three rollers. When printing promotes the construction of Yucheng bioengineering Utilization Technology Research Institute (the unit is in the pressed state), the spacing between the embossing roller and the printing plate roller is basically the same as that between the printing plate roller and the embossing roller. Namely: 0.38mm (thickness of double-sided adhesive) +1.70mm (plate thickness of JG158 (2) 004 rubber powder polystyrene particle external wall external insulation system) =2.08mm. When the old-fashioned unit is pressed, place the kraft paperboard at both ends of the roll gap, and manually adjust the spacing between the embossing roll and the plate roll, and between the plate roll and the embossing roll, taking the same resistance of pulling the kraft paperboard 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, which requires operators to make fine adjustments in normal production. The gelas flexographic printing machine introduced by our factory has changed this series of cumbersome steps in design. It uses a special pressure positioning hole to position the positioning hole, which can more accurately ensure the printing pressure between the three rollers. However, the pressure value of this positioning also needs to be adjusted appropriately in actual production

before starting production, we first carry out pressure positioning for each color deck and relax the pressure between the plate roller and the embossing roller (pay attention to the synchronization of the operating surface and the transmission surface). When the flexographic press is running at a slow speed, start pressing from the printing unit of the first color group, first observe whether the ink transfer between the inking roller and the embossing roller is uniform, 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 the picture and text are printed on the composite sheet (pay attention to keep the synchronization between the operating surface and the transmission surface, whether the force on the test piece is normal, and ensure that the pressure is increased at both ends at the same time and evenly). Check whether the printed points on the sheet are clear, whether the pattern and text are complete, and whether there are problems such as whiteness and emptiness 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 printing pressure is far less than that of offset printing and gravure printing. When setting the flexographic printing pressure at ordinary times, it is mainly required to be small. However, in the case of hose printing, the printing pressure should be deliberately increased slightly because the substrate is a composite sheet. Taking the field version as an example, we adjust the printing pressure to vaguely see the pressure frame on the edge of the field, so as to avoid the white leakage of printed graphics and texts caused by the uneven thickness of the composite sheet per unit area

requirements for printing equipment and consumables

1 Requirements for flexographic printing machine

hose printing uses composite sheet, a material with high cost, as the substrate, so the performance requirements of flexographic printing equipment are higher than those of ordinary flexographic printing. The printing equipment must be equipped with corona treatment device, and the printing unit is equipped with a full UV curing system. What's more, the equipment needs to have an accurate tension control system and the overall stability of the whole machine, and the printing quality control is convenient, The printing speed is fast, and the product variety change flexibility is high. 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, hose printing is still dominated by imported equipment

2. Requirements for ink

flexographic printing belongs to relief printing. Although it has a history of nearly 100 years, the popularity of UV ink in domestic flexographic printing is only a few years. Compared with water-based inks and solvent based inks, UV inks have high viscosity and poor leveling in eye adjusted hose printing, resulting in poor ink uniformity of the wrinkle roller. During operation, it is necessary to increase the pressure between the wrinkle roller and the plate roller to show the hierarchical effect of the print. However, such operation often causes problems such as paste, reduction of printing plate printing resistance, and insufficient color saturation of printed matter. At present, water-borne UV ink has been developed abroad, which greatly improves the above situation, but the price is relatively expensive. In use, waste is often caused by improper operation. From the perspective of economic benefits, employees need to have a strong heart and pay attention to daily saving

3. Requirements for substrate materials

substrate materials account for the largest proportion of hose printing costs. However, in the printing process, many waste products are often caused by the unstable quality of the sheet, such as the different tightness at both ends of the composite sheet, the surface wrinkle and rib burst, the uneven thickness per unit area, the large change of the internal friction coefficient and other problems are all factors that cause the decline of the yield. At present, hose printing requires very high printability of composite sheets. We hope that domestic manufacturers of composite sheets can further improve their overall quality and stabilize their printability, so that printing enterprises can better control hose printing quality and save product costs, so as to achieve the purpose of win-win between suppliers and users

existing problems and solutions

due to the offset printing used in the outer packaging of the hose, many designers will take the offset printing sample to the hose printing, and hope that different printing methods can achieve exactly the same effect, which will never get satisfactory results. When designing the draft, designers should try to choose large pieces of field or lines, and choose spot colors, so as to give full play to the bright and eye-catching features of flexographic printing spot colors and high saturation; It is better to leak more white and overlap less between colors, so as to minimize the overprint error during flexographic printing

we expect the printing industry to cultivate more flexographic printing professionals, introduce the process characteristics and performance limitations of flexographic printing, so 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 better serve hose printing

information source: Printing Technology