Analysis and Elimination of Uneven Color on Printing Silk Screen

Printing ink color uniformity is one of the important conditions to measure product quality. However, the main feature of plate printing products is often the large area of ​​the plate, and the amount of ink received is correspondingly large. In this way, if the technical process of each link is improperly checked, it is very easy to cause uneven ink color failure, which affects the quality of the product. For example, the thickness of the ink layer on some products is uneven or the ink color is uneven before and after a batch of products, and even produces fish scale-like fine spots or streak-like ink marks.

Analysis of the main reasons are as follows:

1. Poor accuracy of rubber roller, improper adjustment of rubber roller position and uneven distribution of ink caused by too hard colloid

When the rubber roller shaft head is worn or the rubber roller and the ink-inking iron roller are in poor contact, it is impossible to achieve a more uniform ink distribution and ink transfer. In addition, when the inking roller colloid is too hard, it is easy to slip in the ink distribution process of the plate surface, which causes the defects of printing streaks and uneven ink, which affects the printing quality of the plate surface. Yinmao supplies rubber rollers for Heidelberg, Manroland, KBA, Komori and other original machines. It has the characteristics of longer service life, higher efficiency, and more environmental protection.

2. Ink fountain iron roller grinding loss circle and the edge of the steel sheet are curved

Uneven ink delivery caused uneven ink layer. When these conditions exist, it is necessary to take corresponding repair measures, try to keep the iron roller with better concentricity, and grind the edge of the steel sheet into a straight line, so that the ink roller on the ink fountain can control the size of the ink output flexibly, so as not to produce The prints are unevenly colored in the longitudinal direction.

3. Ink color unevenness 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 delivered by the ink fountain is thick, and it is not easy to be evenly coated. After transferring to the plate surface and printing, fine scales often appear The spot is due to the paper's absorption of ink is less than the adhesion of the ink on the printing plate. India.com sells DIC New Century UV3021 UV curing viscosity reducer online, which can effectively reduce ink viscosity and increase fluidity.

4. Uneven printing pressure or poor solid support

Layout ink layer cannot be transferred to the substrate evenly. When the printing pressure is uneven or insufficient, the ink layer on the plate surface cannot be transferred to the substrate evenly or completely, which makes the ink layer of the printed product inconsistent or inked. In addition, if the bottom plate is used to print a larger area of ​​the plate in the embossing process, the bottom plate is easy to compress and deform, and the solidity is not enough. In this way, the ink layer of the printed product often produces unrealistic and uneven shapes, and the batch products There is a tendency for inconsistencies in ink color before and after. Therefore, the embossing process should use metal plate sticky plate to ensure the printing quality.

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

The larger the printing plate surface, 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 to the printing plate and the paper's adsorption of ink, it will inevitably occur locally The ink layer is cracked and cannot be transferred evenly and completely to the paper surface. Therefore, for printing large-area plate products, it is advisable to use a rotary press with a round flattening structure or a rotary press with a round press to make the printing ink color uniform. The multi-linked bill rotary printing machine, purchased on the printing cat net, efficient and labor-saving, worthy of you!

6. Insufficient ink stroke caused by uneven ink stripe density

The difference in 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 defects in the ink fountain structure, it is impossible to adjust to a very accurate uniformity of longitudinal ink delivery. For this reason, some automatic printing machines are additionally provided with several sets of iron rollers that function as ink inking, and the size of the tandem stroke can be Make adjustments at will. When printing a product with a large amount of ink, the cross-travel stroke of the cross-ink iron roller should also be adjusted to ensure uniform ink distribution.

7. Printing bar marks cause uneven ink layer

The so-called printing "bar marks", also known as "back glue shadow", commonly known as "rubber roller marks". It is also a common process defect in the plate printing process, that is, there are one or more ink traces with obvious differences in ink color density on the horizontal position of the printed product, which greatly affects the beauty of the product. There are many reasons for the printed streak, there are technical reasons for the operation, as well as technical factors. If the printing plate pad is uneven or too high, the printing pressure is too heavy, the inking roller is too hard to slip or its height is poorly adjusted, the inking roller is not used enough, the amount of ink is not enough, or the gap between the roller shaft head is a printing bar The source of traces. In addition, factors such as ink hue, ink color density difference, and poor adjustment of ink viscosity are also one of the reasons for printing streaks. Therefore, every link of printing technology should be properly managed to effectively prevent the printing defects of uneven ink layer. In short, there are many reasons for uneven printing ink color, which must be carefully analyzed, and appropriate measures should be taken to control the printing process technology to ensure printing efficiency and quality.