Talking about Several Technical Problems in Screen Printing of Steel Drum(2)

Second, the adhesion of ink on the drum is poor

When the surface of steel drums is printed with graphics, the steel drums are generally coated with paint. Due to the paint on the surface of the steel drums, there is even a certain amount of dust and oil, which can cause poor adhesion between ink and steel drums. In addition, the ink itself The poor adhesion will also directly result in poor adhesion of graphic images on the drum surface. If the user has special requirements in terms of graphic adhesion, it is best to replace the ink with strong adhesion for printing. Improper use of thinner can also cause poor adhesion of the ink film. Therefore, when selecting the drum ink dilution solvent, it is necessary to consider the nature of the ink, so as to avoid the ink and steel drum bond is not strong.

Third, after the printing of steel drums, the edges of the graphics are irregular, with burrs and incomplete phenomena.

After the drums are printed, there are often serrated burrs on the edges of the graphics, including incomplete or broken lines. There are many factors that cause such problems, but mainly due to the quality of the screen version. We analyze from the following aspects:

1. The quality of the sensitized adhesive on the screen is poor, and the resolution is not high, resulting in broken or incomplete lines.

2. When the exposure time is insufficient or the exposure time is too long in the plate making process, the development is not sufficient, and the edge of the screen printing graphic is not neat, and there will be sawtooth. A good screen version, the edges of the graphic should be smooth and tidy.

3. The surface of the screen plate is not smooth. When printing is performed, there is still a gap between the screen plate and the steel drum. Due to the ink penetrating into the air, a burr occurs on the edge of the printing ink.

4. In the printing process, due to swelling of the printing film after exposure to the solvent, and the degree of swelling in the latitude and longitude is different, the surface of the printing film is uneven. During the printing, the gap between the screen plate and the steel drum partially appears. When the ink is suspended, the ink film will have burrs.

To prevent the occurrence of jagged burrs, when making screen plates and screen plates, you should:

1. When making a plate, you should choose the screen with a higher mesh number as much as possible.

2. When making plates, the best quality and high resolution photosensitive materials should be selected.

3. When applying glue to the screen plate, be sure to pay attention to the thickness of the film. If the film thickness is thin, the expansion deformation will be large.

4, as much as possible using diagonal stretch law stretching net, under normal circumstances, the angle of 22 .5 ° is the best.

5. If the printed artwork lines are fine, the indirect plate making method should be used as much as possible, because indirect legal plates generally do not have burrs.

6, in the plate making and printing process, try to control the temperature expansion factor, the use of a small thermal expansion coefficient of the photosensitive material.

7. Improve the quality of plate-making to ensure that the surface of the screen plate is smooth and smooth, and the edges of the screen lines should be neat.

8, the use of spray guns spray screen version to improve the development effect.

9. The distance between the screen plate and the steel drum, the angle of the scraper and the pressure of the stamp should be appropriate.

Fourth, the uneven thickness of the surface of the ink drum graphic

The thickness of the ink film printed on the surface of the drum is not uniform, and the reasons for this phenomenon are various. In terms of ink, it is mainly because the ink is improperly blended, or the ink is blended in the normally formulated ink. When printing, the solvent expands and softens due to the effect of the solvent, and the ink penetrates through the mesh opening to prevent the ink from passing through.

In order to prevent such failures, the ink after dispensing (especially the ink that has not been used up for the last time) must be filtered before use and then used again. Every time the printing is completed, the printing plate must be washed with thinner and dried before it can be stored in the warehouse. When keeping the screen printing plates, be sure to pay attention to dust, moisture and hard, sharp object collisions and scratches.

In screen printing, the main function of the squeegee is to fill ink, evenly ink, scrape ink and imprint. Therefore, when the scraper scribes images on the steel drum, under the effect of the imprinting force, the ink can not only be printed on the steel drum through the screen plate, so that the ink is fully filled into the screen mesh, and Under the effect of the imprinting force, the squeegee squeezes the ink and scrapes from one end of the printing plate to the other. However, due to uneven force or damage to the cutting edge of the front end of the squeegee, an uneven thickness of the ink layer or a trace along the direction of movement of the squeegee may occur during the squeegee printing process. Therefore, the edge of the scraper must be well protected so that no damage occurs. If there is damage, it is necessary to grind it with a grinder or a surface grinder.

Fifth, the size of the drawings on the steel barrel is enlarged

After the screen printing, sometimes the size of the picture on the steel drum is enlarged. The main reason for this phenomenon is the low viscosity of the ink and the excessive flowability; in addition, the size of the screen plate is enlarged during the production, which also causes post-press printing. One of the factors that increases the size of the graphic and text.

In order to avoid the ink flowability caused by the overflow of the ink after printing, resulting in increased size of the graphic after printing, you can add a certain amount of thickener in the ink of excessive fluidity, in order to reduce the flow of ink, also Fast-drying inks can be used to speed up the drying of the ink after printing and reduce the flow of ink. When making a screen layout, the quality of the screen plate must be strictly guaranteed.