Screen Printing Faults and Countermeasures

Screen printing failures are caused by many factors, including screen printing plates, screen printing squeegees, screen printing inks, screen printing equipment, screen printing materials, and operating techniques. In the fore chapters and sections of the book, there are targeted introductions to the troubleshooting and exclusion of silk screen printing. This section will introduce the universal silk screen failures and countermeasures for readers' reference.

There are single reasons for the occurrence of silk screen failures, but more are the result of the cross-cutting effects of intricate causes. This is the operator's judgment of the cause of the failure, and the corresponding countermeasures must be taken.

First, paste version

The paste version, also known as plugging, refers to the phenomenon that the hole of the screen printing plate can't transfer ink to the printing material during printing. The appearance of this phenomenon will affect the printing quality, even if it is severe, it will not be able to print normally.

The cause of the stencil phenomenon in the screen printing process is intricate. The reasons for plagiarism can be analyzed from the following aspects.

The reason for the substrate. Screen printing substrates are diverse, and the texture characteristics of substrates are also a factor in the stencil phenomenon. For example, substrates such as paper, wood board, and fabrics have low surface smoothness and poor surface strength, and are prone to powdering and hair loss during the printing process, resulting in stencil printing.

The reason for shop temperature, humidity and ink properties. Screen printing shop requires a certain temperature and relative humidity. If the temperature is high and the relative humidity is low, the volatile solvent in the ink will evaporate quickly and the viscosity of the ink will become high, thus blocking the mesh. Another point that should be noted is that if the downtime is too long, it will produce a paste version phenomenon, the longer the paste version becomes more serious. Second, if the ambient temperature is low and the ink flowability is poor, it is easy to produce a paste.

Silk screen printing reasons. The prepared screen plate can be used after being rinsed with water and dried before use. If the printed version is left over for a long time and is not printed in time, the dust will adhere to more or less during the preservation process. If printing is not performed, it will cause a paste plate.

The reason for printing pressure. Excessive embossing force during the printing process will cause the squeegee to bend. The squeegee is not in line contact with the screen plate and the substrate, but is in surface contact. This will not clean the ink with each squeegee, leaving a residue. Ink, after a certain period of time will cause conjunctiva caused paste version.

Reasons for improper clearance between screen plate and substrate. The gap between the screen printing plate and the substrate should not be too small. After the gap is too small, the screen plate cannot be separated from the substrate. When the screen plate is lifted, some ink adheres to the bottom of the plate. This is also easy. Cause paste version.

The reason for the ink. When the particles of the pigments and other solid materials in the screen printing ink are large, the phenomenon of blocking the mesh holes is likely to occur. In addition, the mesh size and through-hole area of ​​the selected mesh are smaller than those of the ink, so that it is one of the reasons why the coarse-grained ink does not easily pass through the mesh. For stencils caused by large particles of ink, it is possible to solve the problems when manufacturing the ink. The main method is to strictly control the fineness of the ink.

The ink is dried too fast during the printing process, which can easily cause stencil failure. This is particularly true when using volatile drying inks, so it is important to choose the right solvent to control the drying speed when printing. In the selection of ink to take into account the impact of climate, generally in the winter using fast-drying ink, in the summer should be added to the ink in the dryer, if the use of late drying agent also occurs paste version, you must change to other types of ink.

Oxidation-drying inks are used, and the phenomenon of stencil printing does not appear much. However, if the desiccant is used excessively in summer, stencil printing may occur, and desiccants must be controlled in summer.

When using a two-fluid reactive type ink, since the ink itself is slow to dry, there is almost no stencil printing, but occasionally, stencil printing occurs.

In the printing process, the viscosity of the ink is increased, resulting in a paste plate. The main reason is that the solvent of the ink on the plate evaporates, resulting in an increase in the viscosity of the ink and a screen-sealing phenomenon. If the area for printing graphics is large, the ink on the screen printing plate will consume more, and the stencil printing will be less. If the picture area is small, the ink consumption on the screen printing plate is small, it is easy to cause the paste plate, and the countermeasure is to change the ink frequently.

Poor flow of the ink will cause the ink to produce a paste when not passed through the screen. This can be solved by lowering the viscosity of the ink to increase the fluidity of the ink.

After a paste failure occurs, an appropriate solvent scrub can be used depending on the nature of the ink on the plate. The method of scrubbing starts from the printing surface and gently wipes from the center to the periphery. Check the plate after wiping, if any defects should be promptly repaired, and re-start printing after repair. It should be noted that the plate is thinned each time it is scrubbed, and if it is wiped out, it causes a major defect in the plate.