Analysis of uneven printing ink

Printing ink uniformity is one of the important conditions for measuring product quality. However, the main feature of the plate printing product is often the large plate area, and the amount of ink received is also relatively large. In this printing process, if the technical processes at each link are not properly controlled, it is extremely prone to uneven ink failure and affect product quality. For example, some product layouts are uneven in ink thickness, or the ink density varies before and after a batch of products, and even produce process defects such as scaly fine spots or streak-like ink marks.

The main reasons for the analysis are as follows:

1. The poor accuracy of the rubber roller, improper adjustment of the position of the rubber roller, and the unevenness of the glue caused the ink to be uneven. When the rubber roller head wears or the contact between the rubber roller and the iron chain roller is poor, uniform ink distribution and ink transfer cannot be achieved. In addition, when the ink recoating roller is too hard, the slippage during the printing process of the layout may cause the problems of uneven printing marks and uneven ink printing, which affects the printing quality of the layout.

2. The roller loss of the ink fountain roll and the edge of the steel sheet are severely curved, resulting in imbalance of the ink layer causing ink layer unevenness. In the presence of these conditions, corresponding repair measures must be taken to make the iron roll maintain a good degree of concentricity and trim the edges of the steel sheet into a straight line, so that the size of the ink roll on the ink fountain can be controlled flexibly so as to avoid Prints are unevenly colored longitudinally.

3. Ink viscosity is too large and the ink layer thickness is uneven. When the stroke of the ink fountain roller is too small, the gap between the steel sheet and the iron roller is too large. At this time, the ink layer of the ink bucket is thick, and it is difficult to be evenly coated. After transferring to the printing surface, the fine scales often appear. The spot, which is due to the paper's ability to absorb ink less than the ink's adhesion on the plate.

4. The uneven printing pressure or the lack of firmness of the plate supports can make the printing ink layer of the layout not be uniformly transferred to the substrate. When the printing pressure is not uniform or insufficient, the ink layer on the plate cannot be uniformly or completely transferred to the substrate, so that the ink layer of the ink is not uniform or ink is not true. In addition, if the embossing process adopts a large-scale plate printing on a wooden tray, because the bottom tray is easily deformed by compression, the firmness is insufficient, so that the printed ink layer may also produce false and inhomogeneous products. It is prone to inconsistencies in ink before and after. Therefore, the embossing process should adopt a metallic printing plate to ensure the printing quality.

5. The printing area is too large, and the equipment structure performance is not suitable to cause uneven ink layer. The larger the printing plate surface, the stronger the adhesion between the ink layer and the printing plate, so that due to the unbalance between the adhesion of the printing ink and the printing plate and the adsorption force of the paper to the ink, it is inevitable that it will be locally produced. The ink layer is cracked and cannot be uniformly transferred to the surface. Therefore, the printing of large-area plate products should adopt a rotary flatbed printing machine with a round flattening structure or a round press rotary printing machine to make the printing ink uniform.

6. Insufficient stroke of the ink string causes ink stripe unevenness. The difference in the thickness of the ink layer in the longitudinal position of the print is also a common condition in graphic printing. This is because of the structural defect of the ink fountain, which cannot be adjusted to a very precise longitudinal uniformity of the ink transfer. For this purpose, some automatic printing presses are provided with several sets of iron rollers that play a role of ink stringing, and the size of the stroke can be increased. Feel free to make adjustments. When printing products with high ink volume, the stringer stroke of the chain iron roller should also be adjusted to ensure uniform ink distribution.

7. Printed marks cause ink unevenness. The so-called print "bar marks", also known as "back glue shadow", commonly known as "colloidal roller marks." It is also a common process defect in the printing process of the plate, that is, one or more traces of the bar shading in the horizontal position of the printed product show a significant difference in ink shade, which greatly affects the aesthetic sensitivity of the product. There are many reasons for the print marks. There are technical and operational factors as well as technical factors. If the printing plate pad is uneven or too high, the printing pressure is heavy, the ink roller is too hard to slip, or its height is poorly adjusted, the ink roller is not used properly, the amount of ink is not enough, or the gap between the rubber roller head wears, etc. Trace of the source. In addition, the ink hue, the difference between the shades of ink, poor ink viscosity adjustment and other factors, but also one of the reasons for the production of print marks. Therefore, all aspects of good printing technology should be effectively implemented to effectively prevent the uneven printing of ink layers.

In short, there are many reasons for the inhomogeneity of the plate printing ink, which must be carefully analyzed. Corresponding measures should be taken in a targeted manner to shut down the printing technology to ensure the printing efficiency and quality.