The secret to solving uneven ink color

Printing ink color uniformity is one of the important conditions for measuring product quality. However, the main feature of plate printing products is often that the plate area is large, and the ink volume is correspondingly large. In this way, in the printing process, if the technical process in each link is not properly checked, it is extremely easy to cause uneven ink color and affect product quality.

① Poor accuracy of the rubber roller, improper adjustment of the rubber roller position and too hard colloid cause uneven ink distribution

When the rubber roller shaft head is worn or the rubber roller is in poor contact with the ink roller, it is impossible to achieve more uniform ink distribution and ink transfer. In addition, when the inking roller colloid is too hard, it is easy to slip during the printing process of the layout, causing the defects of printing streaks and uneven inking, which will affect the printing quality of the layout. 

② The black iron roller grinding loss circle and the steel sheet edge are severely curved

The imbalance of the ink supply causes uneven ink layer. When these conditions exist, corresponding repair measures must be taken to keep the iron roller as concentric as possible and to grind the edge of the steel sheet into a straight line, so that the ink output of the ink roller on the ink fountain can be controlled flexibly to avoid The prints have uneven color in the longitudinal direction. 

③ Uneven ink color caused by too much ink viscosity and thick ink layer

When the stroke of the ink fountain iron roller is adjusted too small, and the gap between the steel sheet and the iron roller is adjusted too large, the ink layer of the ink fountain roller is thick, and it is not easy to be evenly coated. After being transferred to the plate and imprinted, fine scales often appear The spots are caused by the paper's adsorption of ink being less than the ink's adhesion on the printing plate.

④ Uneven printing pressure or insufficient plate support

The ink layer of the layout cannot be transferred evenly to the substrate. When the printing pressure is uneven or insufficient, the ink layer on the plate surface cannot be transferred evenly or completely to the substrate, causing the ink layer of the printed product to be inconsistent or improperly inked. In addition, if the embossing process uses a wooden base to print a larger area of the plate, because the base is prone to compression and deformation, and the firmness is insufficient, the ink layer of the printed product will often be unreliable and uneven. It is prone to have different ink shades before and after. Therefore, the embossing process should adopt the metal plate support to stick the plate to ensure the printing quality.

⑤ The printing area is too large, and the structure and performance of the equipment are not compatible, resulting in uneven ink layer

The larger the printing layout, the stronger the adhesion between the ink layer and the printing plate. In this way, due to the imbalance between the adhesion of the ink and the printing plate and the adsorption force of the paper on the ink during imprinting, it is inevitable that it will occur locally, so The ink layer is cracked and cannot be transferred to the paper evenly and completely. Therefore, for printing large-area plate products, it is advisable to use a rotary flatbed printing machine with a circular flattening structure or a circular circular rotary printing machine to make the printing ink uniform. 

⑥ Insufficient ink flow stroke causes unevenness of ink color stripes

The difference in the thickness of the ink layer in the longitudinal position of the printed product is also a common situation in plate printing. This is because of the structural defects of the ink fountain, it is impossible to adjust the uniformity of the longitudinal ink delivery very accurately. For this reason, some sets of iron rollers for stringing ink are added to some automatic printing machines, and the stringing stroke size can be adjusted. Make adjustments at will. When printing products with a large amount of ink, the stroke of the ink roller should also be adjusted to ensure uniform ink distribution. 

⑦ The unevenness of the ink layer caused by the printing mark

The so-called printing "stripe marks" is also called "back rubber shadow", commonly known as "rubber marks". It is also a common process defect in the plate printing process, that is, there are one or more shadow marks with obvious differences in ink color in the horizontal position of the printed product, which greatly affects the aesthetics of the product. There are many reasons for printing bump marks, including operational technical reasons and process factors.

If the printing plate pad is uneven or too high, the printing pressure is too heavy, the inking roller is too hard and easy to slip or its height adjustment is not good, the number of inking rollers is not enough, the amount of ink is insufficient, or the rubber roller shaft head wear gap, etc., are all printing machines. The source of scars.

In addition, factors such as ink hue, difference in ink color density, and poor adjustment of ink viscosity are also one of the reasons for printing streaks. Therefore, each link of the printing technology should be properly controlled to effectively prevent the printing defects of uneven ink layer.

In short, there are many reasons for the uneven ink color of the plate printing, which must be carefully analyzed, and corresponding measures should be taken to control the printing process technology to ensure the printing efficiency and quality.