Talking about several technical problems existing in screen printing of steel drums (3)

Talking about several technical problems existing in screen printing of steel drums (3)

6. After the steel drum is printed, the surface ink will crack and split.

After the steel drum is printed, the cracking phenomenon of the graphic is mainly caused by the action of the solvent and the large temperature change. In addition, when the graphic is scraped on the steel drum by the scraper, if the pressure of the scraping plate is insufficient, the viscosity of the ink is large and the flow is not smooth, which may cause the printing ink layer to be unreal and white spots appear; if the pressure of the scraping plate is too large, When the fluidity is high and the viscosity is low, the ink penetrates between the edge of the plate and the steel drum, and the ink is liable to be inwardly returned. Under the pressure of the squeegee, when the ink is transferred to the surface of the steel drum, at the moment of leaving the plate, the ink is pulled apart between the steel drum and the screen plate, and is transferred to the surface of the steel drum and adhered to the screen plate. In part, the following situations will occur:

1. The ink is filled into the gap of the screen plate.

2. The ink is subjected to the pressure of the squeegee and is in a contracted state.

3. When the plate is off the plate, the ink is pulled between the wire mesh and the steel drum.

After the ink is pulled off, the viscoelasticity returns to its original state. This splitting phenomenon depends on the viscoelasticity, the speed of the release, the interfacial tension between the ink and the screen plate, and the absorption of the ink by the steel drum. The splitting phenomenon is an important factor in studying the formation state of the ink layer.

In order to prevent the occurrence of cracking and splitting of the ink layer, when selecting a solvent, the properties of the ink and the solvent resistance after coating on the surface of the steel drum must be taken into account, and the temperature and humidity at the printing site are taken care of, so that the ink can be effectively prevented. Cracking and splitting of the membrane occurs.

Seven, silk screen leakage ink

When printing graphics on the surface of the steel drum, it is forbidden to mix dust and dust into the surface of the steel drum. Because these dusts are not treated, during printing, the film may be damaged due to the pressure of the squeegee, and pinholes may be generated due to insufficient exposure during plate making, and these factors may cause the film to leak. At this time, tape paper or the like can be attached from the back of the screen plate for emergency treatment. If this operation is not very rapid, the ink on the screen will be dried and the entire layout has to be wiped with a solvent. The wiping plate is also a factor in the peeling of the plate, so it is best to avoid it. In addition, the ink leakage of the screen plate often occurs in the portion where the ink stays, so it is preferable to strengthen this portion at the time of plate making.

In the process of printing the steel drum by hand, first check whether the ink is pure, and do not mix iron filings, iron thorns and dust. Also check that the surface of the steel drum is smooth and avoid dust and iron thorns. Because the sharp corners easily pierce the screen film, resulting in ink leakage. Therefore, the screen version must be inspected and reinforced before printing. In addition, it is necessary to carefully carry out the graphic error and the pinhole correction of the plate to reinforce the periphery of the plate. The so-called reinforcement is to force some plastic tape on the back of the screen plate. Try to avoid the printing in the plate due to the screen version and ink, scraper and other failures to stop working.

8. The ink and flying ink of the graphic after the printing of the steel drum

(1), ink

The ink is a blotted print on the surface and the neutral part of the surface of the steel drum. This phenomenon impairs the printing effect, and the reasons for this phenomenon are:

1. The printing speed and the drying speed of the ink are too slow.

2. The ink layer of the ink is too thin.

3. The thixotropy of the ink is too large.

4. When printing, the effect of static electricity on it is generated.

5. The polarity of the pigment particles in the ink, the particles condense each other, and a color dot blot appears.

How can we improve and eliminate the phenomenon of ink absorption? In general, start with the following aspects:

1. Improve the fluidity of the ink;

2. Use a fast drying solvent;

3. Print as much as possible with high viscosity inks;

4. It is recommended to use ink made of pigment with small oil absorption;

5. Minimize the effects of static electricity.

(2) Flying ink

Flying ink is the drawing phenomenon of ink. The reasons for this phenomenon are:

1. The ink is not evenly ground;

2. The scraper is slower than the plate when printing;

3. There is less space around the printed graphic;

4, the generation of static electricity, resulting in ink drawing;

5. The angle of the scraper is too small.

The solution is:

1. Replace the ink with better quality. When mixing the ink, be sure to stir evenly;

2, pay attention to the speed of the printing when printing;

3. Appropriate gaps should be left in the making of plates;

4, often check and repair the scraper blade.