Talking about several technical problems existing in screen printing of steel drums (2)

Talking about several technical problems existing in screen printing of steel drums (2)

Second, the adhesion of the ink on the steel drum is poor

When the surface of the steel drum is printed, it is generally that the steel drum has been painted. Since the surface of the steel drum is covered with paint and even has some dust and oil, these will cause poor adhesion between the ink and the steel drum; The poor adhesion will also directly lead to poor adhesion of the surface of the steel drum. If the user has special requirements in terms of image adhesion, it is best to replace the ink with strong adhesion for printing. If the diluent is improperly selected, the adhesion of the ink film may be poor. Therefore, when selecting the drum ink to dilute the solvent, the properties of the ink must be considered to avoid the adhesion of the ink to the steel drum.

3. After the steel drum is printed, the edges of the graphic are not neat, and there are burrs and defects.

After the drum is printed, there are often jagged burrs on the edges of the image, including defects 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 photosensitive adhesive coated on the screen is poor, and the resolution is not high, resulting in broken lines or defects in the fine lines.

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

3. The surface of the screen plate is not flat. When printing, there is still a gap between the screen plate and the steel drum. Due to the infiltration of the ink, the edge of the printing ink is burred.

4. During the printing process, due to the expansion of the plate film after contact with the solvent, and the degree of warp and weft expansion is different, the surface of the plate film is uneven. When printing, there is a gap in the contact surface between the screen plate and the steel drum. When the ink is suspended, the ink film will be burred.

In order to prevent the appearance of jagged burrs, when making screens and using screens, you should:

1. When making plates, you should choose a wire mesh with a higher mesh number.

2. When making plates, the photosensitive materials with good quality and high resolution should be selected as much as possible.

3. When applying the 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, try to use the oblique stretch net method to stretch the net, under normal circumstances, the angle is 22.5 ° is the best.

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

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

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

8. Spray the screen plate with a water spray gun to improve the development effect.

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

Fourth, the thickness of the ink on the surface of the steel drum is uneven

The thickness of the graphic ink film printed on the surface of the steel drum is uneven, and the reason for this phenomenon is various. As far as the ink is concerned, the ink is mainly mismatched, or the ink is mixed into the ink which is normally formulated. When printing, the ink expands and softens due to the action of the solvent, and the ink-permeable mesh is clogged, so that the ink cannot pass.

In order to prevent this kind of malfunction, the formulated ink (especially the ink that was not used up last time) must be filtered once before use. After each printing, the printing plate must be washed with thinner and dried before being stored in the warehouse. When storing screen plates, be sure to pay attention to dust, moisture and collisions and scratches of hard, pointed objects.

In screen printing, the main function of the squeegee is to fill, level, smear and emboss. Therefore, when the scraper prints the graphic on the steel drum, under the action of the embossing force, the ink can not only be printed on the steel drum through the screen plate, so that the ink is sufficiently filled into the mesh of the screen, and Under the action of the embossing force, the squeegee squeezes the ink from one end of the printing plate to the other end. However, due to uneven force or damage to the edge of the front end of the squeegee, uneven thickness of the ink layer may appear or a trace may appear along the moving direction of the squeegee during the squeegee process. Therefore, the cutting edge of the front end of the squeegee must be well protected from damage. If there is damage, it should be ground with a grinder or a surface grinder.

5. The size of the graphic on the steel drum is enlarged.

After screen printing, the size of the image on the steel drum is sometimes enlarged. The main reason for this phenomenon is that the viscosity of the ink is relatively low and the fluidity is too large. In addition, the size of the screen plate is enlarged during the production, which also causes the post-press. One of the factors that expand the size of the graphic.

In order to avoid excessive ink flow and cause the ink to overflow around after printing, the size of the image after printing becomes larger, and a certain amount of thickener can be added to the ink with excessive fluidity to reduce the fluidity of the ink. Fast drying inks can be used to speed up the drying of the ink after printing and reduce the flow of ink. When making the screen layout, the quality of the screen version must be strictly guaranteed.