Factors affecting uneven ink color in products:

1. Printing scratches cause uneven ink layer thickness. The so-called printing "bar marks", also known as "back glue marks", commonly known as "glue roller marks". It is also a common process flaw in plate printing, which is the appearance of one or more distinct ink intensity differences in the horizontal position of the printed product, greatly affecting the aesthetic appeal of the product. The causes of printing scratches are multifaceted, including technical and technological factors. Uneven or excessively high plate padding, heavy printing pressure, hard ink rollers that are prone to slipping or poor height adjustment, insufficient number of ink rollers used, insufficient ink volume, or worn gaps on the rubber roller shaft are all sources of printing scratches. In addition, factors such as ink hue, differences in ink color intensity, and poor adjustment of ink viscosity are also one of the reasons for the occurrence of printing scratches. Therefore, it is necessary to effectively control all aspects of printing technology and effectively prevent the printing problem of uneven ink layers.

2. Insufficient ink stroke caused uneven ink color strip thickness. The vertical position of the printed product produces differences in the thickness of the ink layer, which is also a common situation in plate printing. This is because of the defects in the structure of the ink hopper, which makes it impossible to adjust it to a very precise vertical ink transfer uniformity. Therefore, some automated printing machines have several sets of iron rollers that play a role in ink transfer, and their stroke size can be adjusted freely. When printing products with a large amount of ink, the stroke of the iron rollers for ink transfer should also be increased to ensure even ink distribution.

3. The printing area is too large and the equipment structure and performance are not suitable, resulting in uneven ink layers. The larger the printing plate, the stronger the adhesion between the ink layer and the printing plate. This imbalance between the adhesion between the ink and the printing plate and the adhesion of the paper to the ink during embossing may occur locally, leading to the rupture of the ink layer and the inability to transfer evenly and completely to the paper surface. Therefore, when printing large-area graphic products, it is advisable to use a rotary platform printing machine with a round press flat structure or a rotary printing machine with a round press circular shape to achieve uniform printing ink color.

4. Uneven printing pressure or insufficient firmness of the plate holder prevent the ink layer from evenly transferring onto the substrate. When the printing pressure is uneven or insufficient, the ink layer on the layout cannot be evenly or completely transferred to the substrate, resulting in uneven ink thickness or uneven ink application. In addition, if the embossing process uses a wooden base to print a larger area of the plate, due to the compression deformation and insufficient solidity of the base, the ink layer of the printed product often produces unevenness and unevenness, and batch products are also prone to inconsistent ink color before and after. Therefore, the embossing process should use a metal plate holder to ensure printing quality.

5. Uneven ink color caused by high ink viscosity and thick ink layer. When the stroke of the ink bucket iron roller is adjusted too small, and the gap between the steel plate and the iron roller is adjusted too large, the ink layer fed by the ink bucket is thick and difficult to be evenly coated. After being transferred to the printing plate and pressed, fine scale spots often appear. This is because the adsorption force of the paper on the ink is less than the adhesion force of the ink on the printing plate.

6. The iron roller of the ink hopper is severely worn and out of round shape, and the edges of the steel sheet are in a curved shape, causing an imbalance in ink output and uneven ink layer. When these situations exist, corresponding repair measures must be taken,