Common Problems and Countermeasures in Screen Printing (5)

Fifteen, printing ink leak

Part of the printing ink leakage, known as the ink leakage failure, the reasons are: a part of the scraper is injured; the pressure of the scraping ink is large; the gap between the printing plate and the printing material is too large; the plate frame is deformed and the printing pressure is insufficient. The viscosity of the ink is too high; the ink is not uniform; the screen is too fine; the printing speed is too fast.

If the printing material and the ink are mixed with dust and printed without processing, the printing plate will be damaged due to the pressure of the squeegee; when the plate is exposed, pinholes are generated in the wooden foot, and the printing film will leak ink. . At this time, adhesive tapes, etc. can be used for emergency handling from the back of the plate. If this operation is not very fast, the ink on the layout will be dried, and the whole of the plate will have to be wiped with solvent. Wipe plates are also the cause of delamination of the plate, so it is best avoided. The ink leakage of the printing plate often occurs in the ink staying part, so it is better to strengthen this part in the plate making.

In the process of manually printing the binder, when inserting a metal plate and a rigid plastic plate into the printing table, it is easy to puncture the plate with a sharp corner, so be very careful. It is generally best to check and reinforce before printing. In order to prevent ink leakage, the printing plate should be inspected or repaired before printing begins: the pinholes of the printing plate should be filled, the printing plate must be fully reinforced, and printing should begin.

Sixteen, image distortion

The printing pressure applied to the printing plate by the squeegee during printing can bring the line contact between the printing plate and the printed material. It should not exceed. If the printing pressure is too high, the printing plate contacts with the printing material and the screen may expand and contract, causing the printing image to be deformed. Screen printing is the smallest type of printing in various printing methods. If we forget this, we cannot print good prints.

If you cannot print without increasing the pressure, reduce the gap between the plate and the surface of the substrate so that the pressure on the blade can be reduced.

Seventeen, AIDS

Ink-wetting refers to the dot-like blotting of the graphics and dark-sounding parts of the substrate, which impairs the printing effect. In particular, the use of transparent ink is more likely to produce this phenomenon. The reasons are as follows: printing speed and ink drying are too slow; ink layer is too thin; ink thixotropic; electrostatic effects; Dot blots.

The improved methods are: improving the fluidity of the ink; using a fast-drying flux; printing with a high-viscosity ink as much as possible; using as much ink as possible with a small amount of oil; minimizing the influence of static electricity.

Eighteen, flying ink

Ink flying is the phenomenon of ink drawing. The causes are: the ink is unevenly grinded; the squeegee is slow from the print during printing; the white space around the printed image is less; static electricity is generated, resulting in the angle of the ink pulling squeegee being too small.

19. Electrostatic fault

Electrostatic current is generally very small, the potential difference is very large, and there may be the phenomenon of attraction, repulsion, conduction, and discharge. These phenomena will lead to deterioration of the product, degraded performance, fire, fire and human body and other adverse consequences.

1 adverse effects on screen printing. In the screen during printing, the rubber portion and the screen are charged by the pressurization of the blade rubber. If the screen itself is charged, it will affect the normal inking and produce blockage failures; it will be absorbed by the screen at the moment when the substrate is output.

a. Synthetic resin inks are easily charged.

b. Substrate is water-absorbent even though it is papery, but static electricity can also be generated when the air is dry. Plastic substrates have good insulation properties, are not affected by temperature, and are prone to static electricity.

c. The printing area is large and the charging is also large, which is easy to produce bad effects.

d. Since spark discharge can cause flames, be very careful when using flammable solvents.

e. The human body's electric shock due to static electricity is caused by contact with a charged object, or by electrostatic discharges that generate spark discharges when grounded. Although the electric current generated by electric shock is small, no danger will occur, but electric shocks often occur, which will have an adverse effect on the operator's psychology.

2 method to prevent static electricity. The methods for preventing the generation of static electricity include: adjusting the ambient temperature and increasing the air humidity. The appropriate temperature is generally about 20° C. and the relative humidity is about 60%. A small amount of antistatic agent is put into the alcohol used for scrubbing printing materials; the friction pressure and the speed are reduced; Minimize the friction, pressure and impact of substrates; install general grounding devices; use ionization of flame, infrared, and ultraviolet rays; and use ionization of corona discharge with high-voltage currents.